Why Is Rabies The Most Lethal Infectious Disease?

We may not hear of epidemics or pandemics, but…

In bite-size terms…

Rabies is caused by viruses in the Lyssavirus genus, especially the classical rabies virus, which infects the mammalian nervous system and thus can (and all-too-often does) spread through mammals.

Transmission usually occurs through saliva entering tissue via a bite, but even just saliva contacting vulnerable areas can also pose a risk, and infections closer to the head can progress more quickly because the virus travels towards the brain through nerves.

Why rabies is hard to stop: rabies virions can remain hidden for days, months, or (rarely) even years, while suppressing parts of the immune response, and travel inside nerve cells at up to 10cm per day, which helps shield them from immune defenses too.

Once the virus reaches the central nervous system, symptoms begin rapidly as the infection spreads through nervous tissue, initially causing flu-like illness before progressing into severe neurological disease.

Why rabies is so deadly: rabies viruses usually avoid triggering strong inflammation in the brain, preventing immune cells and many therapies from reaching infected tissue effectively, and once symptoms appear, rabies is almost always fatal.

Pre-exposure and post-exposure rabies vaccinations are highly effective if (and usually only if) administered before symptoms develop, preventing the virus from reaching the central nervous system. In contrast, very few people have survived symptomatic rabies, usually after intensive medical care and often with lasting neurological damage.

For this reason, even merely possible exposures, such as waking to find a bat in a bedroom, merit urgent medical evaluation—precisely because rabies prevention is only reliably effective before symptoms begin.

For more on all of this, enjoy:

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Take care!