As our climate changes, conditions are also changing. Now, scientists are identifying new health risks associated with a shifting environment. They've found that new diseases are appearing, caused by previously unknown infectious agents.

The emerging and re-emerging infectious diseases include leishmaniasis, West Nile fever and others. They're actually causing about one third of deaths around the world, and developing countries in particular are suffering from these climate-triggered infections.

What in the climate causes these infections in the first place? Several parameters may be behind this increased spread of pathogens and their host. Climate change modifies temperature and humidity conditions, which alters the transmission dynamics for infectious agents. Climate change also affects the range, abundance, behavior, biological cycles and life history traits of the microbes or host species. That said, this multitude of factors makes it hard to establish a direct link between climate change and the overall evolution of infectious pathologies.

That's why scientists decided to take a bit of a closer look. They found a relationship over a 40-year period between climate change and the epidemics of a disease emerging in Latin America: Buruli ulcer.

Rising surface temperatures in the Pacific Ocean increase the frequency of El Niño events. This, in turn, causes waves of droughts. The scientists compared changes in rainfall patterns with changes in the number of cases of Buruli ulcer. In the end, they found that less rainfall and stagnant water conditions caused an increase in Buruli ulcer cases.

The findings reveal that climate does impact the prevalence of disease. This, in turn, highlights the need to consider a set of parameters and their interactions when forecasting the risk of an epidemic. Not only that, but it shows that contrary to popular belief, less rainfall does not mean a decrease in infectious diseases. Instead, it shows that each disease has its own favorable conditions.

The findings are published in the journal Emerging Microbes & Infections.