The WHO reports (1999) "quantum leaps" in the incidence of malaria around the world coincident with extreme weather events associated with El Nino. Both heat and variations in rainfall affect transmission of the disease by mosquitoes. Kenya and Somalia; tens of thousands of people were affected by Rift valley fever and at least 200 died after the heaviest rains since 1961 attributed to El Nino fell on the region. Cholera has increased markedly over the last year in Latin America and Africa, where an epidemic has been in progress for seven years. The rise in cases is attributed to heavy rainfall and floods associated with El Nino.