Extreme weather events in Malawi and Pakistan have driven "very sharp" rises in malaria infections and deaths, a global health chief said ahead of World Malaria Day on April 25.

Cases in Pakistan last year, after devastating floods left a third of the country under water, rose four-fold to 1.6 million, according to the World Health Organization (WHO).

In Malawi, Cyclone Freddy in March triggered six months' worth of rainfall in six days, causing cases there to spike too, Peter Sands, head of the Global Fund to fight AIDS, Tuberculosis and Malaria, told AFP in an interview.