The vast majority of “emerging” viruses capable of infecting humans have “jumped” from animals to humans. This includes some of the most devastating epidemics on record, such as the ongoing global HIV/AIDS pandemic.
Fortunately it seems that most new viruses that jump from animals to humans are incapable of spreading among the human population. For example, bird flu has repeatedly jumped from poultry to humans, but has not yet adapted to spread directly from those humans to others.
However, some viruses have been able to establish human-to-human transmission after an initial jump from animals, including the Ebola virus, which most likely jumped from fruit bats to humans, and Middle East Respiratory Syndrome (MERS) coronavirus, which jumped from camels to humans.
These differing outcomes led us to ask why only a subset of emergent viruses are able to establish transmissible infections in humans. In other words: what determines the likelihood of a virus’ human-to-human transmissibility?
We thought that biological factors such as the virus’ size, structure and mode of transmission might determine this likelihood. If we could show this to be the case, then identifying the determinative biological factors in emerging viruses could assist public health planning and resource-allocation decisions. New emerging viruses could be categorised according...
