As the planet gets warmer, scientists say, diseases like Zika, chikungunya and dengue will continue spreading farther north. The authors of the new study, published Thursday in the journal PLOS Neglected Tropical Diseases, created a model that includes data on predicted temperature changes and the known range of the day-biting, disease-carrying mosquitoes Aedes albopictus and Aedes aegypti.
Europe will probably see some of the biggest increases in diseases from both of these species, the researchers say. The United States, East Asia, high-elevation parts of central America, East Africa and Canada will also see large increases in risk for these diseases.
The much warmer climates in Southeast Asia and West Africa will not be as suitable for the albopictus species.
This study complements previous work on the link between climate change and bugs, well, bugging us to death. The Fourth National Climate Assessment, published by the US government in November, suggested that North America could see some of the largest increases in disease. Other reports have suggested that climate change could “halt and reverse” progress in human health over the past century.The cases of disease caused by mosquitoes have been increasing. A study in May found that tick- and mosquito-borne diseases have more than tripled since 2004 in the United States. About a sixth of the illnesses and disability cases worldwide come from these conditions, according to the World Health Organization; every year, a billion people are infected and more than a million die from them.
The new study found that the number of people who will be at risk for these diseases in any month of the year will increase substantially by 2050, by about half a billion. By 2080, the number of people at risk in one or more months increases to nearly a billion more than currently expected.
“This model we created is a really large planning tool,” said lead study author Sadie Ryan, an associate professor of medical geography at the University of Florida. She hopes officials will use the work to anticipate problems so they can budget and plan to keep the bugs at bay, as such planning has worked well in the past.
“If you think about why we don’t have malaria in the US now, [it] is because we had incredibly successful vector control,” Ryan said. “We have these tools, but we have to want to use them.”
Ryan cautioned that countries in South and Central America had mostly gotten rid of Aedes aegypti by the 1970s. Their vector control effort was “so efficient. Then we stopped funding it as well, and then it came roaring back in the ’80s.”The study is “provocative” and “well worth paying attention to,” said Dr. Myron Cohen, a professor and director of the Institute for Global Health and Infectious Diseases at the University of North Carolina at Chapel Hill. Cohen was not involved in the study but has worked on research involving mosquito-borne diseases such as Zika.
The important question, he says, is whether politicians and policy-makers — the ones who will need to make the changes to slow climate change and prepare for its consequences — see studies like this and act.
“If Florida, for instance, is going to see a lot of dengue, they’re going to need to be better prepared, and if the southern US is going to suffer more dengue, that would be bad,” Cohen said. “Information like this is very interesting and very important. We hope politicians and policy-makers will get this and act on this concern.”