Assessing the epidemic potential of RNA and DNA viruses

Many new and emerging RNA and DNA viruses are zoonotic or have zoonotic origins, with an animal reservoir that is usually mammalian and sometimes avian. Not all zoonotic viruses are transmissible (directly or via an arthropod vector) between human hosts. Virus genome sequence data may provide the best evidence of transmission. Of human transmissible virus, 37 species have so far been restricted to self-limiting outbreaks. These viruses are priorities for surveillance because relatively minor changes in their epidemiologies can potentially lead to major changes in the threat they pose to public health. Based on comparisons across all recognised human viruses, we consider the characteristics of these priority viruses and assess the likelihood that they will further emerge in human populations. We also assess the likelihood that a virus that can infect humans but is not capable of transmission (directly or via a vector) between human hosts can acquire that capability.