The World Health Organization says climate change endangers human health and developing countries will be most at risk from the increasing spread of disease. The organization is marking World Health Day with a global call to action to help countries adapt to changing climate and reduce its negative health effects. Lisa Schlein reports for VOA from WHO headquarters in Geneva.

Margaret Chan presents 'Protecting Health from Climate Change', during a press conference in Geneva, 07 April 2008

WHO Director-General Margaret Chan provides a nightmarish scenario of the future under climate change. She notes more frequent drought will threaten food security. This will increase malnutrition, which already is responsible for 3.5 million deaths a year.

She says extreme weather events such as storms and floods will spread cholera, typhoid, diarrhea and other deadly diseases. Heat waves in urban areas will increase disability and death, mainly in elderly people.

Dr. Chan says vulnerable people in developing countries will be the first and the hardest hit from climate change.

"For example, just 12 years from now in 2020, crop yields in parts of Africa are expected to drop by half. As another example, women and young girls in parts of Asia currently spend from six to nine hours collecting water. Climate change is adding an additional set of stresses in areas that are already fragile with marginal livelihoods and thin margins of survival."

A farmer waits for rain on his drought hit paddy field in Morigoan in India’s northeastern state of Assam (File)

The World Health Organization says climate change will bring positive and negative health impacts. It says the affects will depend on a country's location and other factors such as rainfall, humidity, and temperature. But, it says the overwhelming impact on health will be negative.

WHO Assistant Director-General for Health Security and Environment David Heymann says changing temperatures and patterns of rainfall are expected to alter the geographical distribution of insect vectors that spread infectious diseases. He says malaria and dengue are among the greatest public health concerns.

"Not only do these diseases occur, they then can get on airplanes or on ships and go to other parts of the world where the conditions are ripe for these diseases, where they have not been previously, but will begin transmission ... This is not itself due to climate change," he said. "But, this shows you that when climate changes do occur in one part of the world, the whole world will be at risk of climate change because of our globalized society."

The World Health Organization says people in rich countries also will be affected by climate change. But, it notes the wealthier countries have better means to deal with the health risks than do the poorer countries.

The World Health Organization says preventive actions are needed to respond to the increased health threats. It says it is very important to establish early warning systems and to help nations strengthen their health systems.