Global warming will pose major threats to the health of the world's population, said Dr. Margaret Chan, secretary-general of the World Health Organization (WHO), which has set "The Climate" as the theme for this year's World Health Day, marked on April 7. The rise in global air and sea temperatures, causing ice to melt and sea levels to rise, she said, will affect not only the environment. "Climate change endangers human health," Chan declared in Geneva. "The warming of the planet will be gradual, but the effects of extreme weather events - more storms, floods, droughts and heat waves - will be abrupt and acutely felt. Both trends can affect some of the most fundamental determinants of health: air, water, food, shelter and freedom from disease." Climate-sensitive diseases, which already kill millions of people a year, include malnutrition, diarrheal diseases and malaria. A European heat wave in 2003 killed an estimated 70,000; Rift Valley Fever in Africa resulted from an excess of rain; Hurricane Katrina in 2005 killed over 1,800 Americans and displaced thousands more; malaria in the East African highlands served as a nesting ground for mosquitoes and spread malaria. Higher temperatures shortens mosquitoes' breeding cycles, causing the insects to multiply at a much faster rate. Flooding and unsafe water in Bangladesh led to cholera epidemics, the WHO chief said. "Although climate change is a global phenomenon, its consequences will not be evenly distributed," continued Chan. "In short, climate change can affect problems that are already huge, largely concentrated in the developing world, and difficult to control." But developed countries will see the growth in urban "heat islands," endangering young and old with cardiovascular or respiratory disease. Higher temperatures can increase ground-level ozone and spur the onset of the pollen season, contributing to asthma attacks. Climate change, concluded the WHO head, also causes masses of people to migrate and diseases to move from one place to another. In Israel, the voluntary organization "Israel For Bicycles" (www.bike.org.il) issued a statement encouraging residents to use bicycles for transport rather than motor vehicles whenever possible. Organization head Yotam Avizohar said on Monday: "Everybody talks about the climate crisis and looks for creative solutions for the future, such as electric cars. But we call to implement - tomorrow morning - plans that encourage daily use of bicycles within cities. More than 90 percent of Israelis live in cities. The state doesn't encourage this or walking, even though these [are healthy]. Bicycle riding," he continued, "won't solve the climate problem, but it certainly has to be part of the solution."