`Prediction will never be perfect'
Olivier Restif, epidemiologist at the University of Cambridge, studies the dynamics of infectious diseases. He spoke to DownToEarth on zoonotic diseases. Excerpts What challenges do researchers in the field of zoonotic diseases face? It often takes several years of painstaking field research to identify the animal species that acted as the reservoir of a particular disease. In the case of Ebola fever, the virus has been found in apes, bats, rodents and more. In each case, it was only in one or a few animals, making it very hard to decide if these were just anecdotal cases or whether we had found the main source of disease. And when you're dealing with a deadly virus, researchers have to take extreme precautions to protect themselves and the people around them. What are the roadblocks to the accurate prediction of occurrence, size or frequency of outbreaks? Once an outbreak has started, we have epidemiological models to help us predict how much they are going to spread and guide interventions. However, just like weather forecast, they are notoriously unreliable in the longer term because we are dealing with very complex systems: it takes just one person getting on a plane to start a pandemic. On a more optimistic note, we are getting much better at estimating risk, so we can direct preventative effort on the regions or the animal species that we have identified as being more "risky", even if we don't know which disease is going to emerge next. Do you foresee the development of such predictive capabilities in near future? Major international programmes are already in place to fill the gaps in our knowledge of the chains of transmission that can result in zoonotic outbreaks. This involves the identification of viruses already pres- ent in wildlife, and a better understanding of how people may come in contact with those viruses. But prediction will never be perfect, so we must learn from recent outbreaks to improve the response. Has there been any noticeable change in the funding available in this field after the international attention the Ebola epidemic received last year? Fortunately, the funding effort in this area had already increased before the latest Ebola outbreak. But emerging diseases, just like climate change or antibiotic resistance, are global threats that require international collaborations, and every country must contribute. Funding for research is important, but we urgently need to see investment in front-line public health infrastructure so that lives can be saved when the next outbreak occurs. Are we more likely to see mosquitoborne diseases like Zika in future? These are the diseases which we expect would increase in response to climate change. Although insect vectors have been travelling from tropical to temperate regions onboard ships and planes for many years, they are now more likely to survive and become established in temperate regions as winters become milder.