Key Takeaways Mosquitoes can carry a range of diseases that pose a risk both at home and while traveling, such as Zika, West Nile virus, dengue and malaria. While most mosquito bites are harmless and only cause a mild irritation, it’s important to watch out for serious side effects or illnesses that could be mosquito-borne. Mosquito activity tends to increase during warmer temperatures and humid climates, so be sure to take more precautions during these times.