World Health Day (April 7) focuses on health threats posed by global warming.

The past 12 years have been the hottest ever recorded on earth, and communities all over the world have been hit by unprecedented floods, wildfires, droughts and tropical storms.

This year's World Health Day (Monday 7 April) is dedicated to "protecting health from climate change", as scientists and governments predict widespread injury and sickness as a result of this global warming.

Flooding, heavy rains and warmer temperatures all facilitate the spread of germs such as bacteria and viruses. In addition, as more people flock to cities after their homes and agricultural livelihoods are destroyed by natural disasters, this will increase the spread of infectious diseases such as tuberculosis and HIV/AIDS.

The World Health Organisation (WHO) warns that the health hazards stem both from "higher risks of extreme weather events" and "changes in the dynamics of infectious diseases".

"The health impacts of climate change are already evident in different ways: more people are dying from excessive heat than before, changes are occurring in the incidence of vector-borne diseases, and the pattern of natural disasters is altering," says the WHO.

Vector-borne diseases are those in which the disease is carried by "vectors" such as mosquitoes and ticks. Already, highlands in Kenya, Burundi and Uganda that were previously considered malaria-free are reporting malaria infections as temperatures increase.

The significant gains made by South Africa to address malaria could well be undermined as a result of hotter weather, floods that increase the breeding areas of mosquitoes and droughts that cause stagnant pools that are the ideal sites for mosquitoes.

"The science is clear," warns the WHO. "The earth is warming, the warming is accelerating, and human actions are responsible. If current warming trends remain uncontrolled, humanity will face more injury, disease and death related to natural disasters and heatwaves; higher rates of food-borne, water-borne, and vector-borne illness; and more premature deaths and disease related to air pollution."

Not only that, continues the WHO, "in many parts of the world, large populations will be displaced by rising sea level and affected by drought and famine. As glaciers melt, the hydrological cycle shifts and the productivity of arable land changes. We are beginning to be able to measure some of these effects on health even now."

There is general agreement that global warming is happening because the earth's atmosphere is becoming overloaded with human-created "greenhouse gases", carbon dioxide and methane.

Carbon dioxide is caused by burning fossil fuels such as coal to generate power - and South Africa is in the process of building new power stations to do precisely these. Methane is released from animals, particularly cattle, as well as landfills.

"Scientists have established that the changes in global climate being experienced by the world today are, in all likelihood ,due to over a century of indiscriminate pumping of carbon dioxide and other greenhouse gases into the atmosphere by developed countries in their pursuit of economic development," says Dr Chukwumerije Okereke, a senior researcher from the University of East Anglia's Centre for Climate Change Research.

"The average American is responsible for the emission of about 125 times more greenhouse gas than the average African. Yet it is Africans who are suffering extended periods of drought, massive crop failure, unprecedented flooding episodes and rapid desert encroachment," adds Okereke.

But global warming can still be reduced, thus reducing the risks associated with it, says the WHO.

Controlling disease vectors (such as mosquitoes and ticks), reducing pollution from transport, and efficient land use and water management are all measures that can help. So can improving the supply of clean water and sanitation and bolstering disaster preparedness in vulnerable areas.

"Scientific uncertainty persists about the possibility and timing of abrupt and catastrophic climate change if temperatures continue to rise," warns the WHO.

"This makes it urgent for action to begin now to stabilize the climate through strong and effective mitigation undertaken simultaneously with adaptation activities to prevent increases in foreseeable climate-related illnesses. Full participation of the health sector in national and international processes for mitigation and adaptation to climate change is essential."

Health Minister Dr Manto Tshabalala-Msimang will address the impact of global warming on the pattern of diseases and health challenges at World Health Day celebrations in Boipatong today (7 April 2008).

"The dialogue on global warming and related health challenges aims to better prepare countries to strengthen surveillance and control of infectious diseases, as well as to ensure safer use of diminishing water supplies and promote better coordination in emergencies," says the Department of Health.