Heavy rainfall precedes outbreaks of mosquito-borne viruses

By Brooks Hays  |  Nov. 22, 2017 at 12:01 PM
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Nov. 22 (UPI) -- New research suggests outbreaks of mosquito-borne viruses Zika and Chikungunya tend to begin three weeks after heavy rainfall.

The latest analysis -- detailed in the journal PLOS ONE -- also showed Chikungunya remains prominent when the two viruses are circulating together, as Chikungunya has a shorter incubation period.

Researchers at UCLA analyzed incidents of Zika, Chikungunya and dengue among several thousand blood and urine samples collected through the Brazilian state of Rio de Janeiro. They organized the incidents by geographic distribution, tracking the timing of infections in cities and neighborhoods. They also compared the timelines of infections with dates of heavy rainfall.

The analysis showed Zika was more common among those without access to municipal water infrastructure, while incidents of Chikungunya were weakly correlated with greater urban density. But the correlation between rainfall and outbreaks of Zika and Chikungunya proved the strongest.

Heavy rains in October 2015 were followed by a massive outbreak of Zika. A decline in Zika cases in February 2016 was followed by a wave of Chikungunya infections.

Zeroing in on weather patterns that predict disease outbreaks could help health officials better contain and respond to infections.

This week, Florida officials confirmed the second local Zika case in the state in 2017.

Previous studies have suggested heavy rain in Florida and the Caribbean can encourage the spread of infectious disease. Mosquitoes lay eggs in standing water, and can proliferate more efficiently in the wake of heavy precipitation.

Health officials worry Puerto Ricans could suffer an increase in mosquito-borne illnesses in the wake of Hurricane Maria's devastating pass over the island earlier this fall.

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