Change in weather patterns, brought on by the 'Godzilla' El Nino of 2015 one of the strongest on record, fuelled the Zika outbreak in South America, scientists have claimed.
El Nino, a naturally occurring phenomenon that sees above-normal temperatures in the Pacific Ocean and causes extreme weather around the world — led to climate change such as severe drought, heavy rains and temperature rises at global scale, which further created conducive conditions for the mosquito vectors, the researchers said.
It was previously 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 Nino that played a key role in igniting the outbreak – almost two years after the virus was believed to be introduced on the continent," said Cyril Caminade, researcher at the University of Liverpool in Britain.
In addition, other critical factors such as the non-exposed South American population, the risk posed by travel and trade, the virulence of the Zika virus strain and co-infections with other viruses such as dengue, might have also played a role in the amplification of the outbreak, Caminade said.
According to Matthew Baylis, Professor at University of Liverpool, "Zika is not going away and so the development of tools that could help predict potential future outbreaks and spread are extremely important."
"Our model predicts a potential seasonal transmission risk for Zika virus, in the south eastern US, southern China, and to a lesser extent over southern Europe during summer," Baylis added.
For the study, the team developed 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 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.
The model can also be adapted to other important flaviviruses, such as Chikungunya and Dengue fever to help health officials prepare for, or even prevent, future outbreaks.
The paper was published in the Proceedings of the National Academy of Sciences (PNAS).