Did you think Zika was scary? Well, take this: global warming endangers up to 1 billion people worldwide at risk of exposure to disease-bearing mosquitoes over the next 50 years, according to new research.
The two most common mosquitoes that transmit the disease – Aedes aegypti is Aedes albopictus – report viruses such as dengue, Zika and chikungunya, as well as more than a dozen others that could become bigger threats in the next half century, the researchers report.
By creating a month-to-month model of temperature changes around the world, scientists analyzed what would happen if these two types of mosquitoes moved with increasing temperatures over the decades.
"Although it is difficult to establish the numbers, we knew that this would be a problem for some time," said study author Colin Carlson. He is a postdoctoral fellow in the biology department of Georgetown University in Washington, D.C.
"The scale of the numbers is definitely terrifying," Carlson added. "If there is a human aspect to this, it is that we were hoping for a different result."
Mosquitoes carry diseases that cause millions of deaths each year, according to the World Health Organization. Dengue, Zika and chikungunya cause symptoms that include fever, rash and severe muscle pain, among others. The Zika virus emerged in Brazil in 2014 and caused serious brain damage to thousands of South American children exposed in the womb.
Carlson and his team found that with increasing temperatures around the world, transmissions may occur throughout the year in mosquito-borne diseases, and seasonal outbreaks could occur almost anywhere. Almost every population on earth could be exposed to these diseases over the next half century.
"The threat is coming"
In the United States, where Zika cases have occurred in warmer areas in recent years, dengue and chikungunya could also become wider threats, Carlson said.
Currently, about 100 to 200 cases of dengue fever occur in the United States each year, especially in people who have traveled abroad, according to the National Institutes of Health in the United States.
"The significance of the study is that we have the ability to know that the threat is coming," Carlson said. "The hope is that we can prevent some of these viruses from settling in the territories of the United States and the United States, but any approach we adopt that focuses only on maintaining tropical diseases outside the United States and Europe is lacking broader framework ".
The researchers' projections also included a surprising discovery: areas like West Africa and Southeast Asia, with the worst temperature increases, could actually become too hot for some disease-carrying mosquitoes.
In this analysis, mosquito-borne diseases such as malaria were not examined, but the common use of window screens in many homes in the United States was a simple and effective way to prevent epidemics, Carlson noted.
The dott. Marci Drees is an infection prevention officer and a hospital epidemiologist at the Christiana Care Health System in Wilmington, Delaware, and was not involved in the new research. But she said she wasn't surprised by her results.
"I think we are all aware of the fact that with global warming and climate change, the habitats of these various vectors – not just mosquitoes, but also ticks and others – will expand," said Drees.
He said that Lyme disease, which is carried by deer ticks, is a prime example of the spread of disease-borne insects related to rising temperatures. "Once quite limited to the Mid-Atlantic and upper Midwest states, Lyme disease is now reported in almost all of the United States," said Drees.
Carlson said he would like his research to be used to plan "basic country-level responses" to climate change and their effects on disease.
"We now have excellent control over what the temperature is doing," he said. "I want to make the leap from risk to the expected load – who gets sick, when and how many people."
Carlson said he was not sure US officials are now ready to face climate change projections that could affect future generations.
"But I think we are at some sort of unprecedented time for climate protection in the United States," Carlson said, adding that social media is helping the public share scientific articles.
"In the end, this is a study of thousands published on climate change and health every year, but hopefully important conversations will start," he said.
The study was published in the journal PLOS Neglected tropical diseases.
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