The study shows that rabies is not always lethal. This understanding, if backed and deepened by further studies, could lead to new treatments. The work implies that some people escape infection after exposure to a small amount of the virus, but Gilbert says it is not clear from the researcher's work if the Peruvians developed true immunity to the virus. Instead the presence of antibodies indicates possible previous non-fatal infection. For now, prevention is the most effective strategy to combat rabies.
Efforts to stamp out the disease through programs that vaccinate domesticated animals such as dogs are largely successful in developed countries, but the rabies virus still kills 55,000 people each year according to the World Health Organization. About 81 percent of rabies outbreaks in Peru from 1996 to 2010 were linked to vampire bat bites, according to the Peruvian Ministry of Health (pdf in Spanish). Vampire bats regularly prey on livestock, but will feed on humans if given the opportunity.
Despite the typically dire consequences, a few individuals have apparently survived rabies infection of the central immune system. An Alaskan trapper may have developed immunity after years of skinning foxes. In 2011, an eight-year-old Californian girl developed the characteristic throat spasms that prevent eating and drinking, traditionally called hydrophobia. The infection reached her cerebrospinal fluid and brain. After intensive care, she made a full recovery.
Most notably, a Wisconsin teenager survived CNS infection after a creative physician put her in a medically induced coma and then administered the anti-rabies virus treatment. He hoped to slow the creep of the disease and give her body a chance to fight back. Since then, several physicians have tried the Milwaukee protocol, but none have replicated the first success.
The discovery of natural antibodies and possible immunity in the Peruvians should not slow efforts to eradicate the disease, Gilbert emphasizes. "Despite finding antibodies in these persons, we don't consider them protected," she says. An editorial that accompanies the research paper echoes her thoughts. The writer, Rodney Willoughby, a physician at the Medical College of Wisconsin, created the Milwaukee protocol. He writes that this discovery is "an opportunity for novel therapeutics" and should spur researchers to find a rabies cure.