STEVE INSKEEP, host:
At the same time that we have to worry about avian flu leaping to humans, we have to worry about this: American health officials are concerned about a new disease that has broken out in Brazil. It mainly affects cattle, but humans get it, too. It does not kill, but it does cause debilitating symptoms. As NPR's Joe Palca reports, the story has a strange twist.
JOE PALCA reporting:
Cases of the new illness have been turning up in Brazil's Minas Gerais state for the past few years. Flavio del Fonseca(ph) is a scientist at Fiocruz, the Brazilian research institute in Bella Horajanshe(ph). He says cows were the first to get sick. They developed sores on their udders. But then people started getting sick.
Mr. FLAVIO DEL FONSECA (Scientist, Fiocruz): They get sick for 21 to 30 days and it's very painful because they can't touch anything 'cause of the lesions; arms are very swollen, and fever, high fever, headaches, and flulike symptoms like that.
PALCA: So far this year, del Fonseca knows of 90 human cases. But he expects to see more. Most of the time transmission went from cow to person.
Mr. DEL FONSECA: But we have two examples that we saw in the field in which the husband, the person dealing with the animals, passed the disease to someone in the household, like one passed to his wife, and another passed to his son.
PALCA: There are several viruses in the pox virus family that cause these kinds of symptoms. But when del Fonseca and his colleagues did a genetic analysis of this pox virus, they found something that astonished them.
Mr. DEL FONSECA: We study five to six genes, and we sequence these genes, and they are 95 to 99 percent identical to vaccinia virus.
PALCA: Vaccinia virus is the one that was used in the smallpox eradication campaign. And it's not typically found in nature. It's close enough to the smallpox virus to cause immunity when used in a vaccine, but different enough from smallpox not to cause disease. Brazil ended smallpox vaccinations 30 years ago. So how did vaccinia from the vaccine turn up in cows and humans in Brazil? And why is it making people sick? Del Fonseca says that's a mystery. Mark Buller is a pox virus expert at St. Louis University. He says vaccinia didn't used to cause illness in animals, either, but Buller says viruses have a way of changing on you.
Mr. MARK BULLER (Pox Virus Expert, St. Louis University): It's quite conceivable that the virus could adapt out of the vaccine to other animals, and why we haven't seen it before this may be a reporting issue. It may be that the infections in the animals were asymptomatic, and only now, for some reason, they've mutated and evolved.
PALCA: Evolving and mutating is something viruses have learned to do in order to survive. Inger Damon is chief of the pox virus branch of the Centers for Disease Control and Prevention in Atlanta. She says the vaccinia virus doesn't mutate as easily as some other viruses, like influenza.
Ms. INGER DAMON (Centers for Disease Control and Prevention): But, saying that, the virus does change and adapt and exploit new ecological niches.
PALCA: Damon is not yet certain the vaccinia virus causing disease in Brazil is from the smallpox virus. She says that's one hypothesis. Another is that the illness is being caused by a new pox virus that just happens to resemble vaccinia. She expects it will be possible to find out which hypothesis is correct.
Ms. DAMON: I think the first step will be to do more extensive characterization of these viruses, and so one potential approach to that is to do full genome sequencing of a number of these vaccinialike viruses.
PALCA: Damon says the CDC will be collaborating with Brazilian scientists in the coming months to start that kind of genetic analysis. Back in Bella Horajanshe, blood samples are arriving at Flavio del Fonseca's lab from patients suspected of having the new disease. Del Fonseca is trying to get a better understanding of how the disease progresses once someone is infected. He's concerned that in the five years or so he's been studying the new illness, each year patients seem to get a little bit sicker.
Mr. DEL FONSECA: Right now it's not a problem. Five years, 10 years, it could become a problem, so we're thinking about dealing with this now before it transforms itself into a problem.
PALCA: Del Fonseca will be coming to Washington next month for a scientific meeting to discuss the best way to stop the disease from spreading. Joe Palca, NPR News.
INSKEEP: This is NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.