You may think of mosquitos as just an annoying pest that will make you itch with a bite, but they can actually be very dangerous. In the U.S., the West Nile virus is becoming increasingly more common. Other diseases mosquitos transmit include dengue fever, malaria, and chikungunya. Almost all of these diseases result in flu-like symptoms and some can be deadly if a doctor is not seen immediately. If you decide to go outdoors, make sure you use insect repellant and keep your skin covered as much as possible.