Birds FluEverything You Need to Know About the Next Pandemic
John Wiley & SonsCopyright © 2006 Marc Siegel
All right reserved.ISBN: 0-470-03864-0
Chapter One BIRD FLU BASICS
What is bird flu?
All bird flus are influenza A. Influenza A is primarily a respiratory virus, causing coughing, congestion, sore throat, muscle aches, fatigue, and fever in most species it infects.
This strain (also called the H5N1 virus) surfaced in Hong Kong eight years ago, although it may have been around for four decades previous to this. It has mostly been affecting Asian poultry. When tested in the laboratory, it has been found to be quite deadly, killing ten out of ten chick embryos against which it was tested. It is difficult to tell how many birds it has killed in Asia, though, because millions of birds have been killed by humans to prevent its spread. As soon as one chicken develops symptoms, it is killed along with all the chickens that may have come in contact with it.
It appears to be quite deadly to humans as well, although in Hong Kong in 1997 many humans reportedly developed antibodies to the virus and did not get sick. There is concern that if the virus mutated, it could cause a pandemic because we do not have built-up immunity to it. This mutation could occur either at random or if the virus mixes its DNA with a human flu virus inside a pig or a human. But it's also quite possible (in fact it's even more likely) that it may never mutate at all or that if it does mutate, the mutated virus would result in a much less severe illness in humans.
What is influenza?
Influenza is a virus. Unlike bacteria, which are single cells, a virus is not a full cell and cannot reproduce on its own. To reproduce, a virus infects a cell and uses the resources of that cell. Essentially, a virus is just a sack of genetic material enclosed by a protein envelope. Viruses don't even fit the definition of "alive," though most scientists agree that they are.
There are two types of viruses: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Influenza is an RNA virus. Influenza comes in two main varieties: A and B. (It also comes in a C, which rarely causes illness.) Influenza A viruses are found in many different animals, including ducks, chickens, pigs, whales, horses, and seals. Influenza B viruses circulate widely only among humans and generally do not make us as sick as influenza A does.
Influenza A viruses are divided into subtypes based on two bumpy proteins on the surface of the virus: the hemagglutinin (H) and the neuraminidase (N). These two identifying proteins are why the current bird flu is referred to as H5N1. There are 16 different hemagglutinin subtypes and 9 different neuraminidase subtypes, all of which have been found among influenza A viruses in wild birds. H5 and H7 subtypes include all the current pathogenic strains.
How does influenza spread and what complications does it cause?
Influenza is spread by airborne droplets and is inhaled into the respiratory tract. It incubates in the body from one to four days before a person feels ill. Complications tend to occur in the very young, in the elderly, and in patients with chronic cardiopulmonary diseases. The major complication of flu is pneumonia from influenza itself, or bacterial pneumonia from pneumococcus or haemophilus.
How is influenza diagnosed?
Influenza is most commonly diagnosed by recognizing symptoms or by direct examination of respiratory secretions. Blood examination (serology) can determine exposure.
What is a pandemic?
A pandemic occurs when many people in several different regions of the world are suffering from a specific illness at the same time. Human pandemics may occur when we are exposed to a virus strain for the first time and we lack immunity to it.
Is there a bird flu test?
The current bird flu is diagnosed by testing the blood for antibodies to the H5N1 strain. The test is 100 percent accurate, though it doesn't tell how sick a bird (or a person) is. Transmission from bird to human is possible but rare, and almost exclusively from close or frequent contact.
How does a bird get it?
It's endemic in birds, especially waterfowl like geese and ducks. It's usually a benign infection of the gastrointestinal or respiratory tracts of waterfowl, and it has existed in birds for many thousands of years. It can pass from wild birds to the poultry on farms when they come into contact, and certain strains, known as pathogenic avian influenza, make these domestic birds very sick. The flu virus mutates frequently, changing its genetics, but it rarely goes through the changes that allow it to routinely infect mammals.
How do birds transmit it to each other?
Birds transmit viruses the same way we do: by sneezing, coughing, and touching other birds.
Is there a cure once you have it?
There is no cure for any influenza for either birds or people. The body's own immune system fights it, and antiviral drugs such as amantadine, ramitidine, Relenza, and Tamiflu are probably all effective against H5N1 bird flu, though the degree of effectiveness hasn't been shown. Although there have been over a hundred reported human cases in Asia, it's not clear if more people have it, but it just didn't make them sick.
With most cases of the annual flu virus, the vast majority of people get better without serious treatment as their immune system fights off the virus. It's the cases where prolonged recuperation or hospitalization becomes necessary that worry doctors.
How fast would a human pandemic spread?
There is concern that air travel would accelerate transmission around the world, although scientific recognition of the mutation early on and the worldwide communication network could help to slow its spread by warning people.
What should I be doing to protect myself?
People are concerned about the possibility of a coming pandemic. The way this information has been communicated in the media and via several of our public health officials carries the message that something major is in the offing. This makes a worst case seem like the only case.
In fact, the government has a reason to consider worst-case scenarios as it attempts to protect us, but we need to consider that a massive pandemic may well not be in the offing. As I suggest here specific measures of personal preparation, I, too, must be careful about hidden messages. When I advise a certain kind of preparation, I must consider if I am inadvertently suggesting that something must be about to happen.
I do not think a massive bird flu pandemic that kills many millions of people worldwide is about to happen, for reasons that I will go into throughout this book. The major reason is that, as with mad cow disease, which has killed hundreds of thousands of cows but only a little over a hundred people, we are currently protected by a species barrier. For bird flu to pass human to human, further changes in its structure have to occur. Influenza viruses change frequently, but this form of H5N1 appears to have been around since the 1950s, and in the eight years that it has infected millions of birds (1997-2005), documented human cases have been rare (less than 150 clinical infections with 70 deaths at the time of this writing). We don't know how many thousands have developed antibodies to this virus and not gotten sick from it, so it may not be as deadly as it seems to be to humans. If it mutates sufficiently to infect us routinely, it may do so in a way that causes it to be far less lethal.
Should I prepare emergency supplies of food and water just in case?
Absolutely not. We've been asking one another this question ever since experts told us that the year 2000 bug in our computers would shut down communications and banking nationwide.
Sinister things scare us out of proportion to their actual risk of affecting us, and we respond, quite naturally, by wanting to be afraid. But bird flu can be seen as one in a long line of things we've been warned about, and for which we supposedly need some kind of "safe room" with an ample supply of food and water just in case.
In one sense, there is little difference between a grizzled terrorist and a mysterious bird flu. Both scare us beyond their reach, beyond the likelihood that they will hurt us. In the wake of 9/11, our leaders have been playing Chicken Little. First it was anthrax, then West Nile virus, then smallpox, then SARS. In each case we were warned that we had no immunity and could be at great risk. In each case there was no accountability going forward, no "We're sorry, we got this one wrong, but we just wanted to prepare you just in case."
It is difficult to trust an official who scared us unnecessarily about smallpox to inform us contextually about bird flu, even if that person is a devoted scientist.
The national psyche has been damaged by all these false alarms. We each make risk assessments, scanning our environment for potential threats, worrying more and more of the time. The emotional center of the brain, the amygdala, cannot process fear and courage at the exact same moment. If we could train ourselves to filter out dangers that don't threaten us by setting our default drives to courage or caring or laughter, we'd be a lot better off.
We don't need emergency supplies of food, we need leaders and information sources we can trust. In a true emergency, our satellite-driven communication system will be our ally, as long as the warnings we receive are accurate and not overblown. Fear is our ultimate warning system, designed to protect us against imminent danger. Our fear responses should not be overdetermined.
By jumping from one fear to the next, we create a climate of distrust. One of my patients told me that he is readying for the coming flu pandemic not only by stockpiling food but by keeping two rifles, ammunition, and a trained German Shepherd at the ready. He envisions a scenario where he may have to barricade himself into his house in order to protect his wife and his two young children. He expects people to be dropping dead in the streets of flu, and he anticipates strangers trying to get into his house to hide from the virus.
This Hitchcockian image is not only extremely unlikely, it contributes to a pattern of thinking that pits us against one another. It is only a half stop from this kind of irrational fright to deep-rooted prejudices where everyone is "the other" and the only way to maintain safety is to cordon off your house.
Should I wash my hands more frequently?
Hand washing is always a good idea as a protection against all respiratory and gastrointestinal viruses, from the common cold to influenza to mononucleosis. Good sanitary practices are essential to not getting the flu if you are in very close contact with it, but more than that, good hygiene is important in not getting any kind of virus or bacteria.
In the fall of 2005, the purchase of hand sanitizers was up almost tenfold. I'm sure this is a response to the fear of getting bird flu. Bird flu is not here, and frequent hand washing or use of sanitizers is a way to reassure yourself in the short term that you are doing something to protect yourself. I would never discourage hand cleansing, but keep in mind that any quick remedy for bird flu fears also reinforces the notion that bird flu is almost here, when there is no evidence to support this. The same is true for avoiding poultry. It may make some people feel safer for a brief moment, but it also reinforces the misconception that our poultry supply is at risk, when it isn't.
Are there specific medical supplies I should stockpile against bird flu? What about Tamiflu?
There is currently no need to personally stockpile anti-virals like Tamiflu (Roche pharmaceuticals) for protection against bird flu. Tamiflu has been tested against this bird flu in mice and is probably effective in humans as well at reducing symptoms, but the doses would probably have to be higher for bird flu than for the usual flu to be effective. It is generally effective when taken in the first forty-eight hours after symptoms begin. A recent study suggests that Tamiflu stockpiles for 25 percent of the population would be sufficient to protect us during a colossal pandemic.
Currently there is no indication for taking Tamiflu for anyone other than perhaps a bird handler or cockfighting organizer in areas of Asia where bird flu is endemic. As with Cipro for anthrax, there is the tendency for fear to create a dependency need for a pill that is not particularly necessary. Not only that, but personal stockpiles remove the physician as an essential filter to decide when a med should be taken. Tamiflu is a well-tolerated drug with nausea as its most common side effect, but taking it when there isn't a situation of true risk from exposure or an ongoing flu is a wasteful use of the drug. Amantadine, an older antiviral drug that is also effective against many strains of influenza A, has been shown in a recent study to have developed a 12 percent resistance to flu viruses because of overuse.
Tamiflu is an expensive drug that has approximately a three-year shelf life, and since bird flu most likely won't mutate to a form that can routinely infect humans over the next few years, the chances are that if you stockpile Tamiflu, you will either misuse it or be compelled to throw it away when it is out of date.
Plus, even if you stockpiled it, without a physician's instructions you'd never know when the appropriate time to take it would be. When there's a rumor of a sick parrot in a cage at LaGuardia? When a human gets it in Madagascar? The first time someone sneezes in your vicinity near the poultry counter of your local supermarket?
How can I protect myself in general against airborne viruses?
This is an important question, and the same basic precautions against all respiratory viruses are applicable to human flu as well as to bird flu if it were to mutate to a human-to-human form. First, frequent hand washing decreases the spread of flu viruses. Be conscious of how often you shake hands or casually kiss someone at a party. These friendly practices spread viruses such as the flu. A sneeze or a cough can propel a virus ten to twelve feet. Cigarette smoke also spreads respiratory viruses, so smokers (and smokers' friends) have to be very careful when they are sick to not blow smoke into a crowded room.
Isolating sick people is the best protection against the spread of flu. Unfortunately, a patient may be spreading the virus for several days before becoming clinically ill. Close contacts of people who are ill should anticipate the possibility of getting sick and in the "window period" should take extra precautions in terms of limiting personal contacts.
What about the yearly flu vaccine?
The yearly flu vaccine is helpful in terms of introducing a "herd immunity," which may protect high-risk groups (the elderly, asthmatics, those with emphysema and diabetes, infants, pregnant women, and the immuno-compromised) by decreasing the amount of circulating flu virus. But a British study this year showed only a mild effect on saving elderly lives.
This result is consistent with a previous National Institutes of Health (NIH) review of the elderly's response to the flu vaccine over the past three decades. But the vaccine is still recommended for those over sixty-five, as it appears to decrease the risk of getting severe complications of the flu, such as pneumonia, which can lead to hospitalization. I recommend the yearly flu shot to anyone in a high-risk group, and I suggest it as an option for anyone who is over fifty or has any chronic illness.
Unfortunately, because the flu vaccine is still made by cultivating the virus in chicken-egg culture (fifty-year-old technology), those with egg allergies often cannot tolerate it.
And as far as anyone knows, the yearly flu vaccine does not offer protection against bird flu. This is subject to some debate, because there is crossover protection from one strain of influenza to another, but significant protection against the H5N1 strain has not been shown. As I will discuss later in this book, there is ongoing research into the development of a single flu vaccine that will cover all strains, including H5N1, and will offer protection for at least ten years. If such a vaccine were commercially available, it would certainly alter prevention strategies for pandemics.