There are two things you can always count on: public radio pledge drives and the local blood bank asking for a donation of a very different sort.

Both kinds of giving can fill you with a sense of goodwill. But, let's be honest, the tote bags help, too.

When it comes to blood donations, though, ethical concerns and risk have led to limits on incentives for donors in many places. The World Health Organization has set a goal for governments around the world to reach completely voluntary and nonremunerated donations of blood by 2020.

The WHO declaration, made in Melbourne, Australia, in 2009, came, in part, because the assembled public health officials asserted their belief that "paid donation can compromise the establishment of sustainable blood collection" from volunteers. Also, paying people to give blood may hurt the quality of donations.

Three economists argue in the latest issue of Science that it's time to rethink restrictions. In the last few years there have been some real-world experiments with incentives that suggest they can help increase donations without causing trouble.

In Switzerland, the reward of a lottery ticket valued at a little over five bucks lifted donations by about 5 percentage points from a base of about 42 percent of the population that typically gave blood. In the U.S., a $10 gift card increased donations by 7 percentage points over the usual 13 percent donation level.

The economists, including Nicola Lacetera of the University of Toronto Mississauga, wrote that the incentives led to quick and localized upticks in donations, which could help with blood shortages.

There are a few things that can be done to minimize potential problems. Offering incentives framed as rewards, rather than outright cash payments, would make sense, for instance.

And giving rewards to people who show up to donate — not just to those people who complete donation — could reduce the incentive for people to lie in order to qualify as a donor. "This practice may be critical for blood safety when incentives are offered," the economists write.

The details can be fiddled with, and researched some more. "But there should be little debate that the most relevant empirical evidence shows positive effects of offering economic rewards on donations," the authors conclude.

This is one of those "good news, but" medical stories.

New treatments for heart failure have made it much less likely that people with this chronic condition will die suddenly.

But an analysis by researchers at UCLA finds that the death rate for people with advanced heart failure remains stubbornly high, with 30 percent of people dying within three years.

"They're not dying suddenly, but their disease is still progressing," says Dr. Tamara Horwich, an assistant professor of medicine at UCLA and a co-author of the study, which was published in Circulation Heart Failure.

Still, that's a lot better than 50 years ago, when heart failure patients were pretty much sent home to die. Heart failure has many causes, including heart attack, diabetes, high blood pressure and viral infections. But the effect is the same: a heart that doesn't move blood effectively.

About 6 million people in the United States have heart failure, according to the Centers for Disease Control and Prevention, and is the primary cause of 55,000 deaths a year.

In the past 20 years, medical care for heart failure has changed radically, with new medications and devices. Horwich and her colleagues wanted to see if these advances were helping patients in the real world.

The people in this study were referred the UCLA center in their early 50s, on average; this is not a disease just for the old. The study looked at 2,500 patients who had been treated at UCLA from 1993 to 2010.

They found that three drugs — ACE inhibitors, beta blockers, and aldosterone antagonists — had been widely adopted for treatment of heart failure between 1993 and 2010. At the same time, the number of people with implanted automatic heart defibrillators went from 11 percent to 68 percent. The implanted defibrillators correct abnormal heart rhythms, a big cause of sudden death.

Death rates were 42 percent lower for patients in the most recent treatment group, between 2005 and 2010, than for the patients in the 1990s. That was largely due to a drop in sudden cardiac deaths.

But deaths from progressive heart failure remained high, with 31 percent of patients dying in the latter part of the study, compared to 36 percent in the 1990s. People could be coming to UCLA sicker than in years past, Horvich speculates, having survived heart attacks and other problems that would have killed them in the past.

But it could also be because those people are ending up on implantable ventricular assist pumps or getting heart transplants, very expensive treatments that are difficult for many people to tolerate.

"We're not curing the disease," Horvich tells Shots. "We're delaying the inevitable." And that means, she says, that "we still have a lot of hard work ahead of us" in finding ways to prevent and treat heart failure.

California just unveiled a wide array of choices for the 5.3 million people expected to qualify to buy coverage through its online marketplace established by the federal health overhaul.

It's the first disclosure of prices in the nation's most populous state for individual health insurance that complies with the Affordable Care Act, and the menu of affordable options surprised some consumer advocates and analysts who had been expecting premiums to be much higher.

"I'm impressed," said Betsy Imholz, director of special projects for Consumers Union. "I actually think they are good prices," she said, especially for those who will receive federal insurance subsidies.

The worry had been that shoppers in the individual insurance market would face sticker shock when the sweeping changes of the health law take effect beginning in January 2014. The law prohibits health plans from rejecting people with pre-existing conditions and doesn't allow insurers to charge women and sicker people more.

Nearly three dozen health plans submitted bids to sell their products in the competitive marketplace, and 13 were selected. But California exchange officials, authorized by state lawmakers to negotiate on behalf of consumers, rejected bids that were too expensive, they said, or failed to include enough choices of doctors and hospitals.

"We've hit a home run for consumers," said Peter V. Lee, the executive director of the California exchange, known as Covered California.

The companies approved to sell individual insurance on the exchange include the state's dominant commercial players, such as Anthem Blue Cross, Kaiser Permanente, Health Net and Blue Shield of California. A number of regional and quasi-public health plans that rely on public and university hospitals and community health centers to deliver medical care to low-wage workers were also approved.

The proposed premiums still need the OK from state insurance regulators. Three of the nation's largest players in the employer-sponsored insurance market — UnitedHealthCare, Cigna and Aetna — aren't going to be selling on the California exchange.

The proposed premium prices vary depending on where in California the buyer lives. Other factors that affect pricing include the consumer's age and the richness of benefits.

Under the premiums unveiled Thursday, a 25-year-old in Los Angeles could choose a Health Net catastrophic plan for $117 a month or a more comprehensive plan for $147 a month from L.A. Care, the nation's largest public health plan.

People making less than about $45,600 per year would qualify for a subsidy that would lower the premiums further.

More than half of Californians shopping for insurance through the state-run marketplace will be eligible for federal income tax credits. Those credits will help offset the price of private insurance: a 40-year-old individual in Los Angeles, for example, who earns $1,915 a month, or 200 percent of the federal poverty level, would pay a monthly premium of $90 for a Health Net HMO "Silver" plan in 2014, according to the rates released by Covered California.

At a media briefing in Sacramento, which had a celebratory air, exchange officials said the restrained premiums largely reflected deft negotiating by the health plans with thousands of doctors and hospitals, including powerful hospital chains whose market clout has been blamed for rising health care costs in California.

"We made the pitch that we can't sustain the current system with 7 million Californians not being insured," said Paul Markovich, president of Blue Shield of California. "We felt there was a rate at which they could still be financially viable, but it would make rates much more affordable for this population."

The rate for an individual plan offered by Blue Shield of California will increase an average of 13 percent for existing customers, said Markovich. But the benefits, he said, as mandated by federal and state regulators and uniform across all health insurance packages, will look more like the comprehensive insurance workers receive from employers.

Health care analysts said simply calculating how much an individual's premium might increase next year was an incomplete — and faulty — assessment of the competitive marketplaces the federal health law was meant to unleash in each state. Caroline Pearson, a vice president at Avalere Health, a consulting firm in Washington, said she judged California's performance by whether residents would have access to insurance products priced around $5,200 a year, the Congressional Budget Office's estimate for an average individual market premium.

And every region in California, based on her analysis, will offer plans below $4,000 a year. The offerings "strike me as very competitive," said Pearson. "It speaks to the number of carriers that were attracted to the market, and that the exchange created competition to drive down prices."

Everybody itches. Sometimes itch serves as a useful warning signal — there's a bug on your back! But sometimes itch arises for no apparent reason, and can be a torment.

Think of the itchy skin disorder eczema, or the constant itching caused by some cancers. "A very high percentage of people who're on dialysis for chronic kidney disease develop severe itch that's very difficult to manage," says Dr. Ethan Lerner, an associate professor of dermatology at Harvard Medical School.

Scientists now say they've got a much better clue as to how itch happens.

For a long time, the thought was that itch piggybacked on the nerves that feel pain or temperature. But it now looks like itch has its own dedicated highway from skin to brain.

And the molecule that makes itch happen comes as a surprise; it usually hangs out in the heart, where it helps control blood pressure.

It's a neurotransmitter called natriuretic polypeptide B, or Nppb.

Researchers at the National Institute of Dental and Craniofacial Research wondered what it was doing in nerve cells. To find out, they created a mouse that didn't make Nppb in its body.

Things that made a normal mouse scratch like crazy had no effect on mice with no Nppb. But when those mice were injected with the substance, they scratched, too.

Nppb seems to be working sort of like an itch-molecule. Take it away and the mice don't itch. Put it back and the itch returns.

The researchers also found a small group of nerves in skin that produce and use this molecule to send an itch message to the spinal cord.

This research hasn't been replicated in humans, so it doesn't prove that human itch works the same way. But the researchers are confident that the molecule is a key clue in defining the long-elusive itch pathway.

The study was published in the journal Science.

Quite a few medical school students have something against obese people, and most of those who have such a bias are unaware of it.

That's the conclusion of study appearing in the July issue of Academic Medicine. It was conducted at the Wake Forest School of Medicine in Winston-Salem, N.C. The study's author says the subconscious judgments could affect how patients are treated.

Here's how the study was done: Researchers gave third-year medical students Harvard's Implicit Association Test on weight. The test is designed to get at people's subconscious biases by measuring how long it takes for them to associate a positive word, such as "love," "laughter" or "pleasure," with a drawing of a person who is either thin or obese.

Psychologists have shown that people's subconscious biases affect how fast they can associate a positive trait with someone they think poorly of.

More than one-third of the students had a moderate to strong bias against obese people, as measured by the test, whereas only 17 percent had an anti-thin bias. Two-thirds of the students were unaware of their anti-fat bias.

Since this study was only done with students in North Carolina, the researchers can't say for sure these attitudes apply to medical school students elsewhere. But given the fact that previous studies have shown that doctors have a similar subconscious bias against overweight patients, it's likely the Wake Forest students are fairly typical.

The researchers for the North Carolina study say medical education should include strategies for recognizing these subconscious biases and guarding against their affecting medical judgments.

How would bias affect the way doctors take care of obese patients? Several ways, study author David Miller told me in an email.

"If doctors assume obese patients are lazy or lack willpower, they will be less likely to spend time counseling patients about lifestyle changes they could make," he said. "Doctors also may be less likely to recommend formal weight loss programs if they assume their patient is unlikely to follow through. "

Miller said bias might also make doctors less effective. "If a patient senses his or her doctor doesn't like them or doesn't respect them," he said, "that will damage the trust that is key to an effective patient-physician relationship."

Scientists have completed the first assessments of how readily the H7N9 flu virus in China can pass among ferrets and pigs. The mammals provide the best inkling of how dangerous these bugs may become for humans.

The news is both bad and good. They've found the new bird virus is easily passed between ferrets sharing the same cage.

"This is a more infectious virus — it has a higher intrinsic transmissibility [among mammals] — than most of the avian viruses we've seen in the past," Dr. Richard Webby, a study co-author, tells Shots.

But the saving grace, so far, is that H7N9 doesn't travel very well through airborne secretions from sneezing and coughing. It requires direct, intimate contact for infection.

Researchers have found that pigs, which often serve as incubators of flu strains that go on to cause big outbreaks in people, can get infected with H7N9. But infected pigs don't pass it on very well, either through direct contact with other pigs or through airborne secretions.

This all fits with the picture that has emerged in China this spring, where H7N9 has so far sickened 131 people and killed 36.

At least three-quarters of those victims apparently got the virus from contact with poultry or markets selling live chickens. Only a few seem to have gotten it from family members. Apparently, no one has been infected by breathing the same air as an infected person.

The new data, published online by the journal Science, come from researchers in China and collaborators in North America. Webby is an influenza expert at St. Jude Children's Research Hospital in Memphis. Other labs have reportedly found the same thing.

But other recent data suggest H7N9 may be evolving into a virus with more ominous implications for public health.

Several Chinese scientists have found a few tiny mutations in two H7N9 viruses they retrieved from a woman who butchered poultry and from chickens in a neighboring stall in a live-poultry market in Nanjing — a city in the epicenter of the Chinese H7N9 outbreak.

Both of these mutations are in a protein called hemagglutinin, found on the surface of flu viruses.

"These findings suggest that the novel virus had been evolving and might, with a few amino acid mutations, adapt to humans," say the authors of a letter published Wednesday evening by the New England Journal of Medicine.

Webby says the H7N9 viruses analyzed so far have receptors that allow them to latch onto cells of both birds and humans. To transmit efficiently between humans, the virus has to lose its avian gene sequences. The Nanjing virus samples seem to be on the way to doing just that.

"On a scale from 1 to 10 — from an avian virus with no potential to infect humans to a fully human-adapted strain — we don't know exactly where this H7N9 is," Webby says. "But I think we can safely say from these data that it might be closer to 10 than the avian viruses we've seen infecting humans in the last decade."

In other words, he thinks H7N9 is close to becoming capable of causing a catastrophic flu pandemic.

Webby says the viruses that caused the 1918 and 1957 flu pandemics had precursors that acquired "humanized" traits "in a stepwise fashion" as H7N9 may be doing.

The latest data add urgency to efforts to squelch the virus's spread among Chinese poultry. Otherwise, H7N9 could become entrenched in poultry populations, as the H5N1 avian virus has.

If that happens, "the opportunities for the H7N9 virus to evolve to acquire human-to-human transmissibility, or to be introduced into pigs, would greatly increase," the authors of the Science paper write.

But how can the spread of the virus in China's live poultry markets be suppressed? Webby says there are ways short of shutting down these markets altogether. "It's not easily done, but it can be done," he says.

In Hong Kong, authorities defeated H5N1 poultry infections by segregating chickens and waterfowl, and by having "clean days" when no imports of new birds are allowed while markets are disinfected.

But the political will has to be mustered to undertake such changes across a wide swatch of China. And Webby worries that the pressure to undertake them will wane as the number of human cases of H7N9 goes down — whether as a result of temporary market closures, as Shanghai has done, or the advent of summertime temperatures less congenial to flu, or both.

"There's a bit of a worry in my mind that the urgency to do something about this will drop," Webby says. "We really need to get on top of this virus and get it out of animal populations. Otherwise it's just not going to go away."

As predicted, abortion opponents on Capitol Hill are wasting no time in their efforts to turn publicity over the recent murder conviction of abortion provider Kermit Gosnell to their legislative advantage.

Their latest goal: a federal ban on most abortions after 20 weeks of pregnancy.

Rep. Trent Franks, R-Ariz., tried unsuccessfully to pass a ban on abortions after 20 weeks in the District of Columbia in 2012. (Congress has special local authority over the nation's capital.) Franks, who chairs the Judiciary Subcommittee on the Constitution, then reintroduced the bill in April.

And now Franks keeps mentioning Gosnell — who was convicted earlier this month of murdering three newborns and one of his female patients — as a major reason not just to pass the bill but to expand its reach nationwide.

"Kermit Gosnell is not an anomaly in this Fortune 500 enterprise of killing unborn children," Franks said at a hearing on the bill Thursday. "Rather, Kermit Gosnell is actually the true face of abortion on demand in America."

Backers of both the federal and state bills chose 20 weeks as the cutoff for abortion because, they say, that is roughly when a developing fetus can begin to feel pain. One of the witnesses at today's hearing, Maureen Condic, a neurobiologist from the University of Utah medical school, testified as much.

"Fetuses at 20 weeks post-fertilization have an increase in stress hormones in response to painful stimuli that can be eliminated by appropriate anesthesia, just as for an adult," she told the subcommittee.

Abortion-rights backers, not surprisingly, disagreed. They presented documents from a list of women's health groups, led by the American Congress of Obstetricians and Gynecologists, suggesting that the science is far from clear, but that most studies still say pain is unlikely before the third trimester of pregnancy (which begins at roughly 28 weeks' gestation).

The broader argument that congressional opponents of the bill make is simpler: Because 20 weeks is still before fetal viability, the bill is, pure and simple, unconstitutional, under current Supreme Court precedents.

Rep. Jerrold Nadler, D-N.Y., read from an appeals court ruling earlier this week that struck down a similar law in Arizona. "A woman has a constitutional right to choose to terminate her pregnancy before the fetus is viable," Nadler said. "A prohibition on the exercise of that rite is per se unconstitutional."

Opponents of the bill also worry that it lacks any exceptions that would allow abortions in cases of fetal anomaly, some of which cannot be detected prior to 20 weeks. Christy Zink of Washington D.C., was faced with one of those situations in 2009, 21 weeks into her second pregnancy.

"An MRI revealed that our baby was missing the central connective structure of the two parts of his brain," she testified. "What allows the brain to function as a whole was simply absent." There was other damage as well. "In effect, our baby was also missing one side of his brain."

Zink had an abortion, and later, a second child. But she told the subcommittee she fears for the doctors who cared for her, and for what might have been.

"If this bill had been passed before my pregnancy, I would have had to carry to term and give birth to a baby whom the doctors concurred had no chance of a life and who would have experienced near constant pain," she said.

Backers of the Franks bill say cases like Zink's are too rare to take into account. They don't worry much about the Supreme Court, either.

Before it was upheld by the Supreme Court in 2007, the "Partial-Birth Abortion Ban Act was struck down by every lower federal court that considered it," Douglas Johnson, of the National Right to Life Committee, said Wednesday at a news conference on the Franks bill. "Three U.S. district courts, [and] three U.S. courts of appeals all ruled it was in clear violation of Supreme Court precedents. But when it reached the U.S. Supreme Court they said otherwise."

Clearly that's what the bill's backers are hoping will happen again — if their proposed legislation gets that far.

Home can be a refuge. But when natural disaster strikes, hunkering down at home can be a deadly mistake.

All told, 32 of the 53 New Yorkers who died in last fall's Superstorm Sandy drowned, and most of them died at home, according to a report published today in the Center for Disease Control and Prevention's Morbidity and Mortality Weekly Report.

They lived in or near a zone of the city that was under a mandatory evacuation order. They drowned when the storm surge flooded homes and cut off escape routes.

Why didn't they leave? Red Cross volunteers gleaned these comments from neighbors and relatives of the deceased: "Afraid of looters." "Thought Hurricane Irene was mild." "Unable to leave because did not have transportation."

Getting people to evacuate when a hurricane or other natural disaster looms is a challenge that has bedeviled public safety officials nationwide for years.

Safety in the face of natural disasters has been on our minds this week because of the devastating tornado in Moore, Okla. People typically have less warning of an approaching tornado than they do of a hurricane like Sandy, making evacuation less of an option. But planning ahead there ups the odds of survival, too. Many homes in Oklahoma don't have basements where people can shelter. But storm cellars or above-ground safe rooms make it more likely that people will avoid injury from debris flung by 200-mph winds, NPR's Jon Hamilton reports.

Today's report on Superstorm Sandy doesn't evaluate whether the people who died received evacuation messages, or whether they were offered help getting out after Mayor Michael Bloomberg ordered that people leave the area on Oct. 29. Though the report notes that the median age of those who drowned was 62, it does not address how this factors into heeding evacuation warnings.

"Given the inability and unwillingness of some residents to evacuate, additional research is needed to identify barriers and motivators for persons during an evacuation and the effectiveness of interventions designed to assist those persons," the authors conclude.

Up until the 1970s, drowning was the most common cause of death in hurricanes, the authors of the MMWR report said. Better weather predictions and evacuation plans had helped reduce deaths by drowning. But in 2005's Hurricane Katrina, and now with Sandy, drowning has reemerged as the greatest danger.

After drowning, the most common cause of deaths directly caused by the storm was being crushed or struck by debris. The most common cause of indirect deaths, many of which happened after the storm, was from carbon monoxide poisoning from generators.

The New York Times has mapped Sandy-related deaths, including the names and ages of those who perished.

And NPR member station WNYC created an interactive map of New York City evacuation zones that can help people figure out what to do in case of hurricanes.

This feels a bit like deja vu.

Scientists report a major breakthrough in human stem-cell research. And then just a week later, the findings come under fire.

Biologists at Oregon Health & Science University said May 15 that they had cloned human embryos from a person's skin cell.

Researchers have been trying to do this for more than a decade. Many scientists in the field were heralding the announcement as discovery of the Holy Grail because now they could make personalized stem cells for treating an array of diseases.

But several images in the paper aren't quite right, a commenter said Wednesday on the website PubPeer.

Specifically, three pairs of photos are duplicated and then labeled as different results. There are also some questions about data demonstrating that the scientists had created stem cells.

The lead author on the study, Shoukhrat Mitalipov, staunchly defended his findings Thursday to the journal Nature. "The results are real, the cell lines are real, everything is real," he said.

Mitalipov claims the problems in the paper were innocent mistakes made because he rushed to publish the findings in the journal Cell.

Right now, the editorial team at Cell supports the study and Mitalipov's claims.

"Based on our own initial in-house assessment of issues raised ... it seems that there were some minor errors made by the authors when preparing the figures for initial submission," Cell's editor Emilie Marcus said on Facebook. "While we are continuing discussions with the authors, we do not believe these errors impact the scientific findings of the paper in any way."

The journal reviewed and accepted the paper four days after receiving it. The paper was then published online 12 days later. Typically, this process takes at least two months and can even last years.

With such a fast turnaround time, some scientists are being careful not to jump to conclusions. "I expect the errors above were also due to the rush to publish." Robin Lovell Badge, at the MRC National Institute for Medical Research in London, told Nature. "The authors should be given a chance to answer and correct mistakes,"

But others think the team should have been more diligent, especially given the past problems in the field.

Back in 2005 and 2004, South Korean veterinarian Hwang Woo-suk published two papers claiming to have cloned human embryos. By early 2006, a committee in Seoul concluded that Hwang fabricated the data in both studies and the journal Science retracted both papers.

"The four-day review process was obviously inadequate," Arnold Kriegstein, of the University of California, San Francisco, told Nature, referring to Mitalipov's study. "It's a degree of sloppiness that you wouldn't expect in a paper that was going to have this high profile. One worries if there is more than meets the eye and whether there are other issues with the work that are not as apparent."

Scientists will know soon enough. It's rather straightforward to confirm Mitalipov's results. If the embryos were indeed created by putting the nucleus of a skin cell into a donor egg, the stem cells will have the exact genetic fingerprint of the skin plus a tiny bit of DNA left over from the egg (specifically, its mitochondria).

Stress can be a bummer for your heart. And, it seems, antidepressants may help some people with heart disease better weather that stress.

That's the intriguing suggestion from a study that tested how people with heart disease reacted when faced with challenging mental and social tests.

People who were on an antidepressant while dealing with these stressful situations were less likely to have myocardial ischemia, a condition in which the heart gets less blood. It can cause chest pain, irregular heartbeat and, in the most serious cases, heart damage.

People are often given a treadmill test to diagnose heart disease. They run, or walk, as fast as they can, and doctors measure how well the heart handles the strain.

But in this study, the stresses were mental and emotional.

Researchers at Duke University Medical Center asked people who had been diagnosed with myocardial ischemia to do challenging tasks: math problems, tracing a diagram while looking in a mirror, and making a speech about a situation that sparked anger or sadness.

Of the 112 people in the randomized controlled trial, half had been taking the antidepressant Lexapro for six weeks before they did the tasks. Sixty-six percent of the people taking antidepressants experienced myocardial ischemia during the tasks, compared to 82 percent of the people not taking antidepressants.

That's hardly a slam-dunk, but it does suggest that the antidepressant could help some people control the mental stress before it starts affecting the body.

"We've long known that mental stress can cause myocardial ischemia, but what do you do, how do you treat it?" asks Dr. Elizabeth Jackson, assistant professor of medicine and director of the women's heart program at the University of Michigan Hospital and Health Systems. She was not involved in the study, which was published in JAMA, The Journal of the American Medical Association.

Patients' mental stress isn't usually tested by cardiologists, Jackson says. This study suggests that "if they're [under] severe stress, maybe we should be looking at that and treating it more aggressively than we do now."

That's not to say that cardiologists should start handing out antidepressants, Jackson told Shots. Other options could help, too, including many that don't involve drugs. "One trial doesn't necessarily mean it's the right thing for everybody."

But this study, she says, is a reminder that "we can't just look at the heart separately. We need to look at people's emotional healthiness to keep them heart healthy."

When it comes to weaning, humans are weird.

Our closest relatives, chimpanzees and gorillas, breast-feed their offspring for several years. Some baby orangutans nurse until they are 7 years old.

But modern humans wean much earlier. In preindustrial societies, babies stop nursing after about two years. Which raises the question: How did we get that way? When did we make the evolutionary shift from apelike parenting to the short breast-feeding period of humans?

Scientists combed the fossil record for clues, but they came up empty until one researcher decided to play tooth fairy.

Manish Arora studies tooth chemistry at the Icahn School of Medicine at Mount Sinai in New York. He knows that teeth hold many secrets.

"You can almost visualize tooth development in terms of growth rings that you would see in a tree," says Arora.

Like tree rings, the layers of enamel and dentin that accumulate day after day mark the passage of time. And the compounds in the enamel can tell scientists a lot about the tooth owner's early growth and development.

But Arora was looking for something very specific: a marker in the tooth that would reveal the timing of weaning. So, he meticulously recorded the breast-feeding habits of women and their babies.

Years later, when the children started to place their lost baby teeth under their pillows, Arora was there to collect them. Luckily, this tooth fairy stand-in had a research grant.

"They do get a small reimbursement for every tooth they donate," Arora says.

When Arora and his colleagues started to analyze the chemical makeup of the teeth, they noticed an interesting pattern in the distribution of the element barium.

"During the period of breast-feeding, the barium levels in teeth were higher," Arora says. "At weaning, the levels of barium in teeth started to drop."

Barium is calcium's cousin (it's in the same column on the periodic table), and it goes where calcium goes. Over the years, it accumulates in our bones. When a mother begins nursing, some of that barium migrates into her breast milk and eventually into her baby's teeth. Arora had found his marker.

He could take a tooth and tell when that tooth's owner stopped nursing. His colleague Tanya Smith, who studies human evolution at Harvard, knew just the tooth to test first.

"It's a first molar tooth from a Neanderthal from a site in Belgium called Scladina," Smith says.

The tooth is 100,000 years old and perfectly preserved. Analyzing the tooth's barium distribution, the researchers determined that this Neanderthal started weaning after about 7 months, and then transitioned to a mixed diet. At 15 months, the barium signal dropped abruptly, as if mother and child had been separated.

The results were published in Nature.

Smith says applying the same technique to other fossilized teeth will help paint a clearer picture of the evolution of human weaning. The shorter nursing times would have given mothers the freedom to reproduce more frequently and gather food for the group. Now we're a step closer to finding out when and how this shift happened.

Arora adds that there's another important application: studying human nursing today. Most breast-feeding studies are questionnaire-based and can be foiled by the faulty memories of their subjects. But with Arora's method, scientists have access to a dental record that always tells the truth.

Scientists have completed an unusual survey: a census of the fungi that inhabit different places on our skin. It's part of a big scientific push to better understand the microbes that live in and on our bodies.

"This is the first study of our fungi, which are yeast and other molds that live on the human body," says Julie Segre, of the National Human Genome Research Institute, who led the survey.

Trillions of microbes live everywhere in and on our bodies. Most of these viruses, bacteria and other microorganisms are harmless. Many of them are actually helpful. But scientists are just starting to figure out exactly what they are and what they do.

"A lot of medicine has to do with not just our own human cells but really [is] about how humans interact with the bacteria and fungi that live on our bodies," Segre says.

To assess the fungal population, Segre and her colleagues collected samples from 14 different patches of skin on 10 healthy volunteers.

"We did an exploration where we looked at all the different little crevices of your body," she says.

The researchers then sequenced the fungal DNA in those samples and report what they discovered in this week's issue of the journal Nature.

"What we found was that the human body is an even more diverse ecosystem than we had known when we looked only at the bacterial communities," Segre says.

The survey turned up dozens of types of fungi — far more than anyone knew were there. In most parts of the body, fungi from the genus Malassezia dominated. One part of the body had an especially wide array: the feet.

For example, researchers found at least 80 varieties on the heel, at least 60 between the toes and at least 40 on toenails. Elsewhere on the body, they only identified between two and five types of fungi.

The researchers aren't sure why feet are teeming with such a broad fungal assortment. One possibility is that temperature of our feet fluctuates a lot. Segre says there may be another, simpler explanation: "Even those of us who wear shoes a lot still walk around barefoot, either in our homes or in locker rooms. And there's just great exposure to fungi."

Whatever the explanation, the survey could eventually lead to new ways to treat millions of people who suffer from all sorts of skin conditions, such as toenail infections and athlete's foot.

"It really would certainly underlie the idea that you really do need to take very good care of your feet," Segre says. "So, for example, I do wear flip-flops when I walk around a locker room because I know from these studies that I don't actually want to share the fungi with the, you know, 20 other people who are showering after just going swimming."

The researchers were also surprised when they discovered that one volunteer's fungi were still out of whack seven months after she had taken an antifungal drug.

"We want to think there is a resilience of our bacterial communities, of our fungal communities, and that as soon as we stop medicating that they would bounce back into a state of health," Segre says.

But the volunteer's experience provides more evidence that this expectation is far from the case. It suggests that all the antibiotics, antibacterial products and antifungal medications people use these days may be affecting the good microbes that live on our bodies more than we think.

"The scale at which people are being exposed to antimicrobial drugs is really substantial," says infectious disease specialist Martin Blaser, at New York University. "And it would be surprising if there were not consequences from that."

Researchers plan to use this survey to explore a number of questions, including why women tend to get yeast infections when they take antibiotics. And why do some people get dandruff and some babies get diaper rash while others don't.

"There will be many further follow-up studies looking at the disease state on the skin and what kind of perturbations are associated with both the bacteria and the fungi there," says Joseph Heitman of Duke University, whose research focuses on microbial pathogens.

The results may also yield insights into skin cancer, he says. "What if we were to find the microbes on the skin either increase or decrease the risk for skin cancer, for example? That might be very important information to have," Heitman says.

Kenya has recorded its first case of polio in two years, the World Health Organization said Wednesday.

A 4-month-old girl came down with paralysis on April 30, and then two healthy kids nearby also tested positive for the virus.

But this handful of infections with poliovirus has the potential to set back global efforts to eradicate polio, WHO spokeswoman Sona Bari tells Shots.

"Polio is a virus that spreads silently," she says. "One case represents between 200 and 1,000 people infected. It's the tip of an iceberg."

Kenya hasn't seen a case of wild polio (as opposed to the rare ones linked to vaccination) since July 2011. And now the risk to neighboring countries is very high, Bari says.

"This is a particularly fragile part of the world in terms of immunity," she says. "Overall, Kenya has a robust health care system, but if polio lands in a pocket with low immunity it could spark a large outbreak."

The new case occurred in the largest refugee camp in the world, the Dadaab Refugee Camp in southeast Kenya. About 500,000 people from neighboring countries live there or move in and out of the camp each year.

"There is a lot of travel through this nexus in Africa," Bari says. Viruses can spread rapidly.

"Last time we saw polio in this region, it caused infections in Sudan, Ethiopia, Somalia and even Yemen." Eventually the virus spread as far as Indonesia and paralyzed more than 700 children.

A few weeks ago, Somalia recorded its first wild polio case in more than five years. A 32-month-old girl became paralyzed in the region near Mogadishu.

Many parts of Somalia have not held polio vaccination campaigns since 2009, Global Polio Eradication Initiative said, and the country, in general, has one of the lowest immunization rates in the world.

Genetic analysis suggests that the poliovirus in Somalia came from Nigeria, which is more than 3,000 miles away. It's still unknown if the Somalia case is connected with the ones in Kenya. But the international health community has responded quickly to contain both outbreaks.

"Fortunately, we're prepared for these things," Bari says. Vaccinations campaigns will start in Kenya this Sunday. In Somalia, they've already immunized about 400,000 children. "About 1 million children will get vaccinated in eastern Kenya," she says.

Such rapid responses are critical if the WHO and other foundations hope to reach their target of eradicating polio by 2018 — a goal that health leaders said would cost about $5.5 billion.

Polio is currently endemic in just three countries: Afghanistan, Pakistan and Nigeria. There were only 223 cases recorded worldwide in 2012 and so far, just 34 in 2013. More than half of the cases occurred in Nigeria.

Great Britain is in the midst of a measles epidemic, one that public health officials say is the result of parents refusing to vaccinate their children after a safety scare that was later proved to be fraudulent.

More than 1,200 people have come down with measles so far this year, following nearly 2,000 cases in 2012. Many of the cases have been in Wales.

Childhood vaccination rates plummeted in Great Britain after a 1998 paper by Dr. Andrew Wakefield claimed that the vaccine for measles, mumps and rubella had caused autism in a dozen children. That study has since been proven fraudulent, but it fueled fears about vaccine safety in Great Britain and the United States.

"This is the legacy of the Wakefield scare," Dr. David Elliman, spokesman for the Royal College of Pediatrics and Child Health, told The Associated Press.

Most of the measles cases have been in children and teenagers between the ages of 10 and 18, according to British health officials. In that age group, vaccination rates dropped below 50 percent in some parts of England after the Wakefield paper was published.

Immunization rates have increased since then, with 90 percent of children under age 5 now fully vaccinated against measles. The BBC has mapped the fall and rise of vaccinations after the Wakefield scare, which closely matches cases in the current epidemic.

"If someone came from another country with measles, it's going to run rampant in an area with a higher percentage of people who aren't vaccinated," says Dr. Aaron Glatt, an infectious disease specialist and chief administrative officer for Mercy Medical Center in Rockville Center, NY. He's a spokesman for the Infectious Disease Society of America.

Each year there are about 60 cases of measles in the United States, according to the Center for Disease Control and Prevention. The disease was declared eliminated in this country in 2000. These new cases are caused by international travelers who bring the virus with them to the U.S.

Research over the past 15 years has shown that childhood vaccines don't cause autism, but parents continue to worry about vaccine safety. About one-third of parents say they worry that small children are getting too many shots too soon.

"Nothing is without any risk," Glatt told Shots, noting that there will always be some risk of side effects and adverse reactions with vaccines. "But the risk of getting measles, which can be a fatal disease, more than outweighs that."

Today more than 1 in every 3 baby boomers — that huge glut of people born between 1948 and 1964 — is unmarried. And those unmarried boomers are disproportionately women. As this vast generation rushes into retirement, there's a growing concern among experts on aging: Who will take care of all these people when they're too old to care for themselves?

It's a question many of the experts take personally. "That is what scares me," says Sara Rix, who works for the AARP Public Policy Institute, studying the economic prospects of women in the workforce. "Because I am one of those people," she says, "and I do think about it."

"Oh, I've got wonderful nieces and nephews," Rix says, noting that's what a lot of her boomer peers claim, too. "Well, in fact, they've got their families. They've got their in-laws. They've got their parents. And I don't think it's reasonable to expect much out of them."

Kathleen Kelly, who runs the Family Caregiver Alliance and the National Center on Caregiving in San Francisco, says she's seeing the same sort of concern in her social circle. "I'm in my 50s, and my friends are all talking about, 'Could we all move in together? Could we buy an apartment building and all live together?' There are all sorts of permutations of this conversation," Kelly says. "But it really is something that people are thinking about, particularly women."

And, because boomers are boomers, some are doing more than just thinking about it. Already, there's a small but apparently growing movement of boomer women forming group houses with their single peers.

One of those homes belongs to Bonnie Moore, a 60-something divorcee who lives in a well-kept, five-bedroom house in Bowie, Md., a cozy suburb of Washington, D.C.

To stay in her house after her divorce, Moore needed financial help. But she wanted to do more than just add boarders who would help pay the bills, she says. The home she's organized instead is "a little bit like family, a little bit like roommates, a little bit like a sorority house," she says from the sofa of her softly lit living room. "It just evolves."

Moore, an attorney, isn't actually childless. She has a grown son who lives in Utah and has been urging Moore to move there to be closer to him and his family. "He's just sort of saying, 'Well, Mom you're old now; we have to take care of you,' " Moore says. "And I'm saying, 'I'm not old. I've got 20 years out there in my yard, thank you very much,' " she says with a laugh.

Moore has been careful about selecting as housemates women who get along, but who also have a sense of independence. "All of us, we have our own separate lives," she says. "We do our own separate things, but we'll meet up in the kitchen and chitchat. And then we'll all go our different ways, which makes it nice. None of us are joined at the hip, and yet we all live together and do our own thing and live in the same house."

Lorene Solivan is one of Moore's three current roommates — "the youngest," Solivan says proudly, having just turned 60.

Solivan, an event manager for a food company, had been living in an apartment in Northern Virginia. But she was having financial troubles of her own and was looking to downsize.

"And then I saw the ad on Craigslist: GOLDEN GIRLS HOUSE. I said, 'Oh, that looks like fun,' " she says.

Solivan, who does much of the group's cooking, says it's been a nice transition for her. To live with a built-in social group of people your own age is "a big plus," she says, "whether you're 20, 40, or 60 — whatever the case may be."

That's why Moore is trying to take her concept and expand it. She already has a website and is working on a guide to help other single boomer women set up houses like hers. "I think it'll be fun," she says. "And I'd like to be part of various seminars and workshops for women [about] the whole idea of living communally and learning to get along in this kind of environment."

Still, there are a lot of obstacles. One big one is that most boomers don't realize they might need help getting or paying for long-term care if their health falters.

"I call it the 70-70-70 conundrum," says Bruce Chernof, president and CEO of The SCAN Foundation, which focuses on long-term health care issues. "Seventy percent of people over the age of 65 will need some form of long-term-care supports as they age," he says. But when you look at polling, "roughly 70 percent of Americans don't actually think they're likely to need it, and roughly 70 percent think Medicare will probably cover it when they get there."

The problem, of course, he adds, is that "those last two 70 percents are not true."

Then there's the numbers problem. "We know that ... about a third of baby boomers are single," says Kelly. "But we also know that there's a large percentage of those that are in their 50s and 60s [who] are getting divorced, and so we're going to have more single individuals in the future. We just haven't seen this before."

At the same time, most boomers have had fewer children than previous generations did, and many boomers have no children.

"So there's less adult children to take the place of the caregiving cohort that currently is providing ... caregiving to their parents," she says. And today, family caregiving provides an estimated $450 billion a year worth of unpaid care.

Rix of AARP says a big problem for single boomer women is that they're not financially prepared to hire the caregivers they might need if they don't have family members to volunteer the time. "[These single women] are still likely to be concentrated in what we've traditionally called the 'pink collar' jobs," she says, which are "the lower-wage, low-benefit occupations. So when they reach old age, they often reach old age without pension coverage."

Most of these women will have Social Security, Rix says — assuming that they are eligible, and that the rules don't change between now and when they retire. But for many older women, that will be all, or nearly all the money they have to live on, she says, "and it's not going to pay for a lot of care — formal care. So it's a frightening future for a lot of women."

There are things women can do to make that future a little less frightening, says Kelly. Some suggestions are pretty obvious, like maintaining a healthy, active lifestyle.

But another bit of advice may be less intuitive, Kelly says, "and that is to invest in social relationships and networks." She doesn't mean the sort of social networks people create on the Internet, but rather, "a community of individuals [living with or near you, so] that you may be able to share tasks and responsibilities as you grow older."

That brings us back to Bonnie Moore, who says that deciding to form a group house was about more than just financial necessity. "I think women naturally are more community oriented," Moore says. "It's just part of the woman's nature."

And besides, she adds, "to come home and have someone say, 'Hi, how was your day?' ... That's really nice sometimes."

So if you're a boomer and you liked that group house you shared in college or just after, good for you. The United States is one of the few developed nations that have no organized public policy for providing long-term care — so group living may be in your future as well as your past.