Viruses 101

What do rabies, cold sores, and COVID-19 all have in common? They are each caused by a viral infection.

Viruses have co-existed with humans from our earliest evolutionary origins—and well before that. To date, scientists have identified at least 219 virus species that are able to cause disease in humans, and a few more are discovered each year.1

That number likely just scratches the surface of the number of viruses that inhabit our world. According to recent estimates, a minimum of 320,000 viruses exist within the mammalian class of animals alone.2 Even more virus species infect birds, reptiles, and plants. According to some estimates, there are 10 million times more viruses on earth than there are stars in the universe.3