Mosquitoes have always been a nuisance, but there are increasing concerns about how they spread disease because of Zika virus. Mosquitoes that spread Zika virus mostly bite during the daytime hours and are also known to spread other diseases, such as dengue and chikungunya viruses. Unfortunately, Zika, which is linked to severe birth defects, can be spread during sex, and there are currently no vaccines to prevent the spread of this disease.