Heavily infected areas are found in Uttar Pradesh, Bihar, Andhra Pradesh, Orissa, TamilNadu, Kerala and Gujarat. The infection is acquired from a person who has filariasis. The maximum infectivity is when the organisms are circulating in the blood. Their usual habitat is in the lymph nodes. The mosquito feeds on such a person and acquires the filarial parasite .The filarial organism is transmitted when the mosquito bites a person .The parasite is deposited near the site of puncture.
Filariasis affects all age groups.