Scientists at the University of Liverpool have shown that a change in weather patterns, brought on by the 'Godzilla' El Niño of 2015, fuelled the Zika outbreak in South America. The findings were revealed using a new epidemiological model that looked at how climate affects the spread of Zika virus by both of its major vectors, the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus).
The model can also be used to predict the risk of future outbreaks, and help public health officials tailor mosquito control measures and travel advice.
The model used the worldwide distribution of both vectors as well as temperature-dependent factors, such as mosquito biting rates, mortality rates and viral development rates within mosquitoes, to predict the effect of climate on virus transmission. It found that in 2015, when the Zika outbreak occurred, the risk of transmission was greatest in South America.
The researchers believe that this was likely due to a combination of El Niño - a naturally occurring phenomenon that sees above-normal temperatures in the Pacific Ocean and causes extreme weather around the world - and climate change, creating conducive conditions for the mosquito vectors.
El Niños occur every three to seven years in varying intensity, with the 2015 El Niño, nicknamed the 'Godzilla', one of the strongest on record. Effects can include severe drought, heavy rains and temperature rises at global scale.
Dr. Cyril Caminade, a population and epidemiology researcher who led the work, said: "It's thought that the Zika virus probably arrived in Brazil from Southeast Asia or the Pacific islands in 2013.
"However, our model suggests that it was temperature conditions related to the 2015 El Niño that played a key role in igniting the outbreak - almost two years after the virus was believed to be introduced on the continent."
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