A number of extreme weather events have been happening around the world this summer, including record flooding in Pakistan that has killed more than 1,000 people and displaced millions of others; the worst drought in Russia in decades, which has triggered wildfires and doubled the daily death rate in Moscow to about 700; and torrential rains in China, which have caused massive flooding and triggered landslides that have killed more than 3,000 people. Meanwhile, here at home, residents in more than 15 states have been sweltering from heat waves that flared in June.

HONG KONG (Reuters) - Nearly 3 billion people, or two-fifths of the world's population, were at risk of contracting malaria in 2009 and closer study of the mosquito's life cycle is needed to combat the disease, researchers said in two reports. In the first study, scientists mapped out the geographical spread of the Plasmodium vivax -- the most common parasite that causes malaria -- using reported cases of malaria and details on temperature and aridity. "We estimate that the global population at risk of P.