Where have all the mosquitoes gone? Parts of the US are seeing a huge drop — and that has experts worried

Read our Privacy noticePesky mosquitoes seem unavoidable in summer but maybe not for long - in parts of the United States, at least. open image in gallery The West Nile virus is seen under a microscope. High numbers of West Nile virus have also been reported in nearby Colorado and Utah. Drought means that mosquitoes breed around smaller bodies of water, giving more opportunity for the virus to spread between them. The West Nile cases are how scientists have been tracking major changes to mosquito populations.