I previously discussed the idea that new human virus infections will continue to emerge from animal hosts. Stephen Morse, my colleague here at Columbia, has called this collection of viruses the ‘zoonotic pool’. How many viruses are in this pool?
Here are Dr. Morse’s calculations: assume that there are 50,000 vertebrates on earth, each of which harbors 20 different viruses. That gives a total of 1 million vertebrate viruses. We have only identified about 2,000 viruses; therefore over 99.8% of vertebrate viruses have not yet been discovered!
In other words, the zoonotic pool is very large – providing many opportunities for new human infections, and for the scientists that study them. This realization has lead to the rapidly growing field of pathogen discovery, of which Ian Lipkin and Joe DeRisi are masters.
Morse, SS. 1993. Emerging viruses. Oxford University Press.
Lipkin WI 2008. Pathogen Discovery. PLoS Pathog 4(4): e1000002.