In 2000 when the Global Programme to Eliminate Lymphatic Filariasis (GPELF) was launched 120 million people in 83 countries globally were infected with lymphatic filarial parasites, and it was estimated that over 1.3 billion (20% of the world's population) were at risk of acquiring infection.  At that time more than 40 million people were thought to be incapacitated or disfigured with lymphoedematous limbs, or breasts, and/or hydrocele of the scrotum.  Affected people were found in the endemic countries the sub-tropical areas of the globe, including the Americas, Africa and Asia, and were living in both urban and rural areas. Lymphoedema distribution LF prevents afflicted individuals from experiencing a normal working and social life, furthering the cycle of poverty.

In 2015, as a result of the Global Programme activities the number of endemic countries has reduced to 73 countries and of the 1.3 billion at risk some 315 million people have now been able to stop taking treatment representing major progress towards disease elimination.

Country treatment detail can be found here

The parasite: 90% of infections globally (100% in Africa) are caused by the filarial worm, Wuchereria bancrofti, with most of the remaining infections by Brugia malayi.  The Brugian parasites are confined to areas of east and south Asia, especially India, Malaysia, Indonesia, the Philippines and China.  Small foci of Brugia timori are also found in Indonesia.  

Humans are the exclusive host of W. bancrofti infections , and even though certain strains of B. malayi can also infect some feline and monkey species, the life-cycle in humans and in these other animals generally remain epidemiologically distinct, so that little overlap exists.

The vectors:  The disease is transmitted by mosquitoes.  For W. bancrofti culicine (Culex) mosquitoes are the major vector in most urban and semi-urban areas while anophelines are the chief vectors in the more rural areas of Africa and elsewhere.  Aedes species. are the mosquito vectors in many of the endemic Pacific iislands.   For the Brugian parasites, Mansonia species serve as the major vector, but in some areas anopheline mosquitoes are also responsible for transmitting the infection.