Aedes aegypti mosquitoes
The mosquito Aedes aegypti is the primary species responsible for transmitting viruses such as Zika, dengue, chikungunya and yellow fever between people. In some communities, other mosquitoes may also contribute to transmission, but their contribution is minor. The World Mosquito Program introduces Wolbachia into Aedes aegypti mosquitoes, which helps to block the transmission of these viruses, which have the potential to cause debilitating and potentially fatal diseases.
Aedes aegypti originates from Africa but is now distributed globally in tropical and subtropical regions. Global redistribution was assisted by mass human migrations, first to the New World associated with the slave trade between the 15th to 19th centuries, and then to Asia as a result of trade during the 18th and 19th centuries. Worldwide redistribution occurred after World War II following troop movement.
In addition to the global distribution of mosquitoes, rapid human population growth and increased urbanisation has led to substandard housing, inadequate water supply and waste management systems, and consequently an abundance of mosquito breeding sites. Storage of drinking water and other urban water, containers including plant-pot bases, guttering, tarpaulins, tyres and discarded containers can all collect rainwater and provide habitats for Aedes aegypti larvae.
Importantly, mosquitoes do not naturally carry viruses. Mosquitoes must acquire them from an infected person before they can transmit them to another person. Only female mosquitoes bite, requiring the blood for egg production, and therefore only female mosquitoes transmit viruses.