More than half a billion people, nearly double previous estimates, were affected by the deadliest form of malaria in 2002, scientists said on Wednesday. Most were in sub-Saharan Africa but nearly 25 percent occurred in south-east Asia and the Western Pacific. "The disease burden is 515 million clinical attacks a year on the planet. That is quite substantial," said Professor Bob Snow of the Kenyan Medical Research Institute in Nairobi, Kenya.
"We have taken a conservative approach to estimating how many attacks occur globally each year but even so the problem is far bigger than we previously thought," he told Reuters.
The figures, which are reported in the science journal Nature, are almost twice those of the World Health Organisation (WHO) which estimated the global incidence of malaria at 273 million cases in 1998 with 90 percent of cases in Africa.
"It is quite substantially higher than the WHO estimate," said Snow who calculated there were 365 million cases of malaria in Africa alone in 2002.
Malaria is transmitted by the bite of an infected mosquito. It occurs in more than 100 countries and kills more than a million people each year.