Mosquitoes are considered vectors, which means they may carry pathogens that can transmit disease from one human or animal to another. According to the World Health Organization (WHO), vectors cause more than 700,000 deaths annually worldwide by spreading infectious diseases. Malaria and dengue are two of the most prevalent diseases transmitted by mosquitoes. Other diseases carried by mosquitoes include: Chikungunya fever, Zika, Yellow fever (or malaria), Dengue fever, West Nile disease and Japanese encephalitis. Most of these diseases are rare and few cases are found within the U.S., apart from the West Nile virus.