A new study by researchers from the CDC in collaboration with the Peruvian Ministry of Health, says that some people living in two Amazon communities in Peru survived exposure to the rabies virus, without receiving vaccination.
The published study, "Evidence of Rabies Virus Exposure among Humans in the Peruvian Amazon," followed a May 2010 survey of two communities located in a remote section of the Peruvian Amazon known for outbreaks of human rabies infections caused by vampire bat bites.
In the communities of Truenococha and Santa Marta, Peru, outbreaks of human rabies infections caused by bat bites have occurred regularly over the past two decades. Yet the study discovered that several people showed signs of surviving rabies bites, even though they had never been vaccinated or treated for the disease.
The study, which appeared in the August issue of the American Journal of Tropical Medicine and Hygiene, involved 92 people, 50 of whom reported previous bat bites. Blood samples taken from 63 people revealed that seven of them were found to have "rabies virus neutralizing antibodies."
This was "evidence that they had been previously exposed to the rabies virus," researchers said, although the study could not determine whether they ever experienced clinical disease. One of the seven had received a rabies vaccination recently, but the other six said scientists, were "unlikely to have received medical care following prior bat bites."
Rabies is the most recognized human health risk from bats in Latin America and is responsible for outbreaks of the virus linked to vampire bat bites among populations living in the Amazon region over the past several decades.
“Nearly all rabies virus exposures that proceed to clinical infections are fatal," said Amy Gilbert, PhD, of CDC’s National Center for Emerging and Zoonotic Infectious Diseases and lead author of the study. But the results she added, "support the idea that under very unique circumstances there may be some type of enhanced immune response in certain populations regularly exposed to the virus, which could prevent onset of clinical illness."
According to the CDC, "rabies has the highest case fatality rate of any conventional infectious disease, approaching 100%," and is most often transmitted through the bite of a rabid animal. Study results however, suggest that exposure to the rabies virus is not invariably fatal in humans. Still, this doesn't mean that people should become complacent about rabies the CDC said.
"Avoiding rabid animal exposures, and receiving injections administered after a person is exposed to rabies virus remain the best ways to protect against acquisition of this fatal disease," the Center explained.
In the United States, human deaths from rabies have declined over the past century from more than 100 annually to an average of two per year. Aggressive campaigns to vaccinate domestic animals against the disease have helped and more recent human rabies cases are primarily tied to bites from infected bats.
The CDC urges any person who has had contact with bats to seek medical advice, and to report exposures to local public health authorities. Rabies infects the central nervous system, ultimately causing disease in the brain and death. For further information about rabies, visit Cdc.gov/rabies.