Some people living in a vampire bat–ridden part of the Peruvian Amazon seem to have developed natural resistance to the rabies virus.
“Why these individuals don’t die is very intriguing,” says CDC disease ecologist Amy Gilbert, who led a study by researchers from the U.S. Centers for Disease Control and Prevention and the Peruvian Ministry of Health.
The detection of anti-rabies antibodies in the blood of 14 percent of healthy individuals tested in two communities suggests that people had been exposed to the virus and survived, the researchers write in the August American Journal of Tropical Medicine and Hygiene. All of those positive for antibodies reported encounters with vampire bats resulting in a bite, scratch or skin contact. Only one person sampled reported having been vaccinated against rabies.
Without immediate treatment, the rabies virus makes its way to the victim’s brain, leading to fever, paralysis, convulsions and death. Every year the virus kills more than 55,000 people worldwide.
Many factors may determine how quickly or whether rabies exposure leads to a full-blown infection, Gilbert says. The relatively gentle bite of a vampire bat may deliver a much lower dose of the virus than, say, a dog or raccoon bite. The proximity of the bite to the victim’s head can also play a role. Perhaps even the genetics of the victim is important.
“Rabies used to be a disease we said was 100 percent fatal. It was the most deadly disease of all diseases,” says infectious disease doctor Carol Glaser, with the California Department of Public Health. But that’s not always the case: Three people in the United States recently survived what appeared to be serious rabies infections. No other disease, not even Ebola, kills everyone it infects, Glaser notes, “So it would make sense that there’s a bit more of a spectrum than we appreciated.”
Gilbert and her CDC colleagues studied two remote communities in the Peruvian Amazon. Neither settlement has formal roads; one of them, Truenococha, is a two-hour boat ride to the nearest health clinic and the other, Santa Marta, a six-hour ride. Several nearby communities have had rabies outbreaks in recent years, so the researchers, along with the Peruvian Ministry of Health, went to investigate the link between vampire bats and exposure to the virus.
The discovery that several people appear to have survived exposure to rabies does not mean that anyone should stop worrying about the virus. “We certainly don’t think these people are protected,” Gilbert says. They still need to get post-exposure treatment following bites.” In fact, in areas where people have fairly regular interactions with vampire bats, routine immunizations, especially of children, are a good idea, she says.