The immune system may be able to defeat rabies even after it reaches the brain – could there be an alternative therapy to the Milwaukee protocol?
Rabies is caused by single-stranded negative-sense RNA viruses in the genus of Lyssavirus. Rabies virus (RABV; genotype I) is the most prolific of the 12 viral species classified within the genus, and it is responsible for greater than 55,000 human deaths annually. Typically, RABV is transmitted in the saliva after the bite of an infected mammal. In the Americas, bats and carnivores are the major reservoirs of RABV. Multiple insectivorous bat species play a role in RABV transmission to humans in the United States.
In 2011, 8-year-old Precious Reynolds of California became only the sixth person known to survive rabies without receiving a vaccine shortly after infection. At the University of California Davis Children's Hospital doctors treated Reynolds with the Milwaukee protocol – an experimental procedure that plunges the patient into a drug-induced coma, taking the brain "offline" while the immune system scours the virus from infected neurons. But the Milwaukee protocol is not a miracle cure for rabies – far from it. Since Rodney Willoughby of the Children's Hospital of Wisconsin in Milwaukee developed the treatment in 2004, the protocol has been tried at least 35 times around the world in attempts to save people with rabies. Including Reynolds, only five have ostensibly benefited from the treatment.
Why has the Milwaukee protocol worked in only a few cases? The answer may be that the survivors owe their lives not to the experimental treatment, but to a combination of fortunate circumstances and a robust response from their own immune systems. New research suggests that rabies is not quite the unequivocally fatal disease we think it is. The six known survivors may have been infected with weak strains of the rabies virus that their immune systems were able to eventually scrub from their brains – with or without the Milwaukee protocol.
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