According to estimates by the World Health Organization, about 51 million people worldwide were infected with filariasis in 2018. In the majority of endemic areas worldwide, microfilariae show a nocturnal periodicity, as they have adapted to the daily rhythm of their vectors (mosquitoes). There are various clinical developments of the infection. The risk of lymphedema and the extent of microfilaremia are likely to be genetically influenced. A high frequency and intensity of the immune response to the dead or dying worm seems to promote the development of clinical symptoms through inflammatory processes, as does the amount of antigen released by the parasite into the lymph vessels. It is suspected that the regular infection-specific immune suppression contributes to the chronicity of the infection. Diagnostics should be carried out in individuals with relevant epidemiological exposure and typical symptoms. Ultrasound, laboratory tests, and lymphoscintigraphy are possible.