**1.2 Epidemiology**

Currently, an estimated 858 million people live in 50 endemic countries [12, 13]. Of these, 65 million people are infected with LF. The majority of these infections, around 90%, are thereby caused by *W. bancrofti*. An estimated 19 million cases with hydrocele and 17 million lymphedema cases exist, leading to 1.3 million disabilityadjusted life years (DALYs) [12, 14, 15]. Most infections with *W. bancrofti* occur in South and Southeast Asia as well as in Sub-Saharan Africa, but also Central and South America, the Middle East as well as the Pacific Islands are endemic regions. *B. malayi* has its distribution in South and Southeast Asia, found in India, Indonesia, Thailand, Vietnam, Malaysia, and the Philippines. *B. timori* is limited to Eastern Indonesia and Timor-Leste. Despite the wide distribution of LF, the prevalence rate has been decreasing in many areas, mainly due to the impact of the Global Programme to Eliminate Lymphatic Filariasis (GPELF). This programme has even led to the elimination of LF in several countries including Togo, Egypt, Maldives, Sri Lanka, Thailand, Cambodia, Cook Island, Marshall Islands, Niue, Palau, Tonga, Vanuatu, Vietnam, Japan, Korea and China [16, 17]. In the last two decades, GPELF has distributed more than 8.2 billion treatments, ultimately leading to this success. GPELF has ended in 2020, but MDAs targeting LF are still ongoing in 45 endemic countries. While the initial goal to globally eliminate LF by 2020 was missed, GPELF has created a good foundation for endemic countries to achieve the goal which the WHO has stated in their NTD roadmap 2021–2030: to eliminate LF as a public health problem in 80% of the endemic countries by 2030 [14, 18, 19]. Further major challenges for the future are increasing population numbers in endemic countries and the associated unplanned urbanization combined with poor sanitary [20].
