As the global community deliberated at the 16th Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC) from this week in Cancun, Mexico, countries from South-East Asia were faced with the task of ensuring that regional concerns were addressed in discussions of the impact of climate change on human health. Climate change strikes at the basic pillars of life - water, food, air, and the ecosystem. Island nations like the Maldives, mountainous countries like Bhutan and Nepal, and countries like Bangladesh, Indonesia, India, Sri Lanka, and Thailand - with large populations living along the coast - are most vulnerable.

The UNFCCC recognised the adverse impact of climate change on human health in 1992. It urged parties to formulate policies and actions to minimise the distressful effects on economy, public health, and the quality of the environment. Yet 17 years later, only 1 of the 47 nations mentioned human health as a consideration in the preparatory submissions to the UNFCCC negotiations for the Copenhagen meeting in December 2009. This silence about health indicates a serious blind spot. Human health seems to be lost in the debate on climate change science, emissions targets and trading, differential responsibilities, and threats to livelihoods and shelter.

More frequent extreme weather events are an expected manifestation of climate change. South-East Asia already bears the burden of the largest number of deaths due to natural disasters. In the last few years, cyclones, floods, and heat waves have killed thousands and left millions more homeless. In addition, climate change is expected to increase the burden of malnutrition, diarrhoea, malaria, and dengue - all of which are climate-sensitive. Such effects are likely to overwhelm the already overburdened health infrastructure in the region.

Among the effects of extreme weather events are water scarcity, crop destruction, and salinisation of fields, problems of food distribution, and increased diseases or pests affecting plants. The increased frequency of extreme weather events under current climate change scenarios would thus have follow-on impacts, such as adding to the global total of food-insecure people. This is why it is so urgent to take action now to avert such effects.

The South-East Asia region is already faced with issues related to large populations, rapid urbanisation, and varied-and sometimes difficult-geographic terrain. In view of such factors, climate change (if not addressed) will have serious negative consequences for the pace of development and may set back progress already made. Ensuring adequate fresh water for populations in the region will be a key issue;by the 2050s more than one billion people could be affected by the lack of fresh water.

Recent predictions regarding climate change-related heat waves are that the number of deaths from such events will increase, especially among the most vulnerable groups which include the elderly, the very young, the chronically ill, and socially isolated people. The greater incidence of heavy precipitation that climate change is expected to bring will lead to floods and landslides. Such events could cause enormous numbers of fatalities and injuries as well as huge economic losses. A variety of sectors-agriculture, settlements, commerce, and transport-would suffer damage. In particular, urban and rural infrastructure would be severely stressed. Because of likely movements of populations due to disasters, member states would also need to take steps in the area of psychosocial support for displaced and affected people.

Dengue and dengue haemorrhagic fever are caused by a virus and transmitted through mosquitoes. In recent years, there has been a significant increase in reported cases of dengue in the South-East Asia Region. Bhutan and Nepal reported cases of dengue for the first time since 2004 and 2006 respectively. Mosquitoes transmitting dengue previously found at a height of 500 metres above sea level have now been sighted at an altitude of 2200 metres in Darjeeling, India, and 4000 metres in Nepal. As a result, vector-borne diseases will expand into new areas whose populations were earlier unexposed to such diseases.

The evidence is clear: climate change will directly impact human health. It is time to act now. Resources need to be channeled to support adaptation measures by the health and environment sectors. The global community needs to support efforts, technically and financially, to protect health from climate change in this region. Health research to estimate the economic impact of climate sensitive diseases on developing countries needs to be prioritised.

Countries from South and South-East Asia have demonstrated political will at the highest level. This is evident in the New Delhi Declaration by the Health Ministers from 11 countries of the region in 2008, which was reiterated more recently by a conference of regional members of parliaments at Thimphu, Bhutan, and in the Dhaka declaration by ministers and senior officers from ministries of health and environment.

But the health effects of climate change-and the damage-are already upon us. It is time for the countries that are most vulnerable to climate change to voice their concerns and ensure that human health becomes the central theme for climate change discussions and agreements.

The writer is deputy regional director, WHO, South-East Asia