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Climate change accelerates infectious disease outbreaks
October 22, 2017, 4:45 pm
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In addition to its role in role in driving devastating natural disasters, global climate change can also spur outbreaks of infectious diseases such as Zika, malaria and dengue, says a new study by researchers at the University of Colorado in the US.

Climate change presents complex and wide-reaching threats to human health as it amplifies and unmasks ecological and socio-political weaknesses that increase the risk of adverse health outcomes in socially vulnerable regions, said the researchers.

The researchers said these vulnerabilities can happen anywhere. After Hurricane Katrina hit New Orleans, cases of West Nile disease doubled the next year. Climate change in Africa appears to be increasing cases of malaria. And the recent destruction in Houston, Florida and Puerto Rico due to hurricanes may usher in more infectious diseases in the years ahead.

The study focused specifically on a magnitude 7.7 earthquake that struck coastal Ecuador in April 2016, coinciding with an exceptionally strong El Niño weather event, which is associated with heavy rainfall and warmer air temperatures. They are also linked to outbreaks of dengue fever.

The researchers noticed a 12-fold increase in Zika cases in the earthquake zone. Prior to this, there were only a handful of Zika cases in the whole country. Zika virus is transmitted by mosquitos. Warmer temperatures and increased rainfall from the El Niño, along with a devastated infrastructure and an influx of people into larger cities from the earthquake, likely increased mosquitos and caused the spike in Zika cases.

The researchers suggest El Niño created ideal conditions for Zika-carrying mosquitos to breed and make more copies of the Zika virus. The warmer temperatures and increased rainfall from El Niño have previously been associated with a higher likelihood of dengue outbreaks. Warmer temperatures can also accelerate viral replication in mosquitoes and influence mosquitos' development and breeding habits.

At the same time, the El Niño event brought warmer sea-surface temperatures, which have been shown to correlate with outbreaks of mosquito-transmitted diseases. Estimates from remote sensing data in coastal Ecuador show that sea-surface temperatures were higher than average from 2014-2016.

The team also believes an increase in water scarcity after the earthquake indirectly benefited mosquito development. The quake damaged municipal water systems, forcing people to store water in open containers outside their homes. These served as additional habitats for mosquito larvae.

The new findings could be used by governments to identify and protect vulnerable communities before natural disasters happen. One idea is to develop disease models that can use existing climate models to predict where these vectors will show up due to climate variability. Applying these new models to areas that have pre-existing social vulnerabilities could identify susceptible regions, allowing us to direct healthcare resources there ahead of time."

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