Viruses aren’t automatically your enemy. These ambiguous, definition-bucking little beasties, found in every single environment on Earth, play a variety of roles – and the ancient precursor to one seems to play a role in how we form memories. Saying that, plenty of viruses can cause lethal infections in humans, with some being deadlier than others.
Without a doubt, influenza is the single biggest killer of them all. Back in 1918, between 50 and 100 million people died after being infected by the virus, which was around 5 percent of the planet’s population at the time. Overall, half a billion people were infected. Far from taking the lives of those that were otherwise vulnerable – the already sick, the elderly, or the very young – it spared no one.
There are several myths surrounding the pandemic, but it’s safe to say that it was the deadliest mass infection in human history. In fact, it’s something that plenty, including Bill Gates, have warned could happen again if we take our eye off the ball, or if we defund key agencies tasked with keeping the wolf from the door.
By total number of deaths, there’s no competition: The H1N1 strain of influenza virus is by far and away the most lethal in this respect. What if, though, we look at the mortality rate of viral infections instead – the number of infected people that ultimately die?
At a rough estimate, based on the high-end deaths value, H1N1’s case fatality rate (CFR) back then was roughly 20 percent. As it turns out, there are viruses that have frighteningly higher CFRs out there in the world today.
Take rabies, for example. This is a disease that, according to the World Health Organization (WHO), occurs in more than 150 countries around the world. It’s present on every single continent, except Antarctica, and 99 percent of human transmissions occur through dog bites. Children aged between 5 and 14 years are the most frequent victims.
Different variants have different incubation periods and epidemiologies. Those with “furious rabies” can become hyperactive and develop a fear of water and sometimes fresh air. A few days later, cardiorespiratory arrest occurs.
Those with paralytic rabies take longer to die. It begins to immobilize your muscles at the bite point, and eventually you fall into a coma and die as your brain and spinal cord continually inflame.