A team of researchers have reviewed what we know about how infectious diseases hosted by bats are passed from them to other animals and to humans. This study reveals how future outbreaks of infectious diseases might be prevented.
Viruses that originate in bats may be the most notorious infectious diseases which can be passed between animals and humans. Viruses which originate in bats include Hendra virus, Nipah virus and Marburg virus. Ebola is another example of a virus harboured naturally in bats, when passed to humans it has devastating and sometimes fatal impacts on those infected.
Bat populations naturally carry infectious viruses. The reason is little understood but one hypothesis is that their immune systems differ from most other mammals, perhaps as a result of their evolutionary adaptations for sustained flight, allowing them to tolerate infections without becoming ill themselves. This makes them excellent hosts for these infections.
For a disease hosted by bats to pass into another population of animals the researchers behind this study have laid out 5 enabling conditions: bats carrying the disease must be present and infected; they must be shedding the virus into the environment, often through urine, saliva or faeces; the virus must be able to survive outside of the body; recipients must be exposed to the virus; and they must be susceptible to the virus. The team say that an intervention at any of these stages could prevent the spillover of diseases carried in bat populations to other animals and to humans.
Understanding how infections filter through ecological systems to cause disease in humans is of profound importance to public health. ‘Tracking the dynamics of emerging diseases from the cell to the landscape will be necessary to assess the weight of evidence for potential causes and to elucidate how human activities affect one or more of the enabling conditions’ say the team.