A new study has revealed that 75 percent of the US may provide suitable conditions for disease-spreading mosquitoes, for at least some of the year. The findings are related to temperature, so global warming might increase chances of invasions from unwanted insects.
Aedes aegypti and Aedes albopictus are types of mosquito that carry deadly diseases like Zika, dengue, and yellow fever. The US Centers for Disease Control and Prevention (CDC) have warned that these mosquitoes could survive in three-quarters of mainland US states.
So far these are just predictions. Potential abundances and disease transmission risks are still unknown. Nevertheless, the new research highlights the need to take precautions and carry out surveillance on previously unmonitored areas, just in case the unwelcome visitors do arrive.
The researchers analyzed records of mosquito presence in US counties to model their full potential range. They found that 71 percent of counties provided suitable conditions for Ae. aegypti, whilst 75 percent could support the survival of Ae. albopictus. The researchers created maps of their predictions to show where mosquito survival would be most likely. They published their findings in the Journal of Medical Entomology.
"These maps show CDC's best estimate of the potential range of Ae. aegypti and Ae. albopictus," said senior author Dr Rebecca Eisen, from the CDC's Division of Vector-Borne Diseases. "In other words, these maps show areas where CDC predicts Ae. aegypti and Ae. albopictus mosquitoes could survive and reproduce if introduced to an area during the months when mosquitoes are locally active."
The scientists found temperature to be the most important predictor of whether the mosquitos would be able to survive. Like a lot of insects, they need warmth to develop. This begs the question, could climate change allow mosquitos to spread to the US more easily?
The CDC had already created a report on county-level mosquito surveillance records for the two species from 1995 to 2016. The new study combined these with historical records stretching as far back as 1960 and county-level climate data reaching back to 1980. The researchers then used statistical analysis to create a model showing which US counties have suitable environmental conditions for the mosquitoes to survive.
The findings are important as they will influence public health and control measures.
"Surveillance efforts can be focused in counties where Ae. aegypti and Ae. albopictus could survive and reproduce if introduced to an area during the months when mosquitoes are locally active or at least survive during summer months if introduced," Eisen said.
"Additionally, the maps can help healthcare providers and the public understand where these types of mosquitoes could be found so that they can take steps to protect against mosquito bites and possible infection."