Every day is dress casual day at the renovated regional headquarters of the World Health Organisation in Manila. With Manila sizzling at 39 degrees Celsius, it's off with the jackets and ties in a 'green office initiative' instituted by Western Pacific regional director Shigeru Omi. Dr Omi says the office apparel is their small way of helping to cool the Earth. It is timely because the issue of climate change, and its consequences for human health, was the theme for this year's World Health Day, which was marked last Monday. A US$10 million regional effort to save the planet comes as the WHO estimates that of the 150,000 deaths a year which are linked to climate change, from diseases and floods, more than half are in Asia. But coming so close to the Beijing Olympics the climate-change theme is a thorny issue for China. With Beijing under fire from activists following the Olympic torch relay, the last thing it needs is to be pressured on is its contribution to global warming. Dr Omi was nonplussed when asked whether the choice of theme for World Health Day was a political decision. 'Our decision has nothing to do with China, let alone the Olympics, but is based on the status of climate change and its potential impact on human health. It has affected every country and every country has to take their share of the responsibility,' he said. WHO spokesman Dick Thompson agrees. 'There were no political considerations about the theme selection,' he said. 'The point was to bring human health into the discussion over climate change.' WHO director-general Margaret Chan Fung Fu-chun, formerly Hong Kong's director of health, will press the point with world leaders at a G8 meeting in Japan next month. 'In selecting climate change as the theme for this year's World Health Day, the WHO aims to turn the attention of policy-makers to some compelling evidence from the health sector,' Dr Chan said. 'While the reality of climate change can no longer be doubted, the magnitude of its consequences - most especially for health - can still be reduced. Consideration of the health impact of climate change can help political leaders move with appropriate urgency.' Dr Chan said the effects of extreme weather events - more storms, floods, droughts and heat waves - 'will be abrupt and acutely felt' but that the effects of a warming planet would be gradual. 'Both trends can affect some of the most fundamental determinants of health: air, water, food, shelter, and freedom from disease,' she said. WHO experts said there was already evidence of indirect links between global warming and the changing epidemiological patterns of mosquito-borne diseases such as malaria and dengue fever, with implications for the mainland and Hong Kong. Hong Kong itself has been trying with success to keep out dengue fever, because once it becomes endemic it can never be eradicated. Its first local outbreak in 2002 was successfully controlled. As of February there had been seven cases this year, all imported. There were 58 cases in the whole of last year and 31 in 2006. There were 33 malaria cases last year and 40 in 2006, but there have been none so far this year. Malaria's link to global warming, said Dr Omi, was straightforward. Malaria-carrying mosquitoes are now found in areas where there were none before, such as the highlands of Papua New Guinea. The link between climate change and dengue fever was less clear, he said, adding that it was too soon to verify a link between the rise in cases and the rise in temperatures. John Ehrenberg, the WHO regional adviser on malaria, vector-borne and other parasitic diseases, said there was enough indirect evidence linking climate change with the spread of vector-borne diseases. Controlling dengue fever in Asia would depend on when it stopped becoming a 'neglected disease'. The WHO will help governments strengthen mosquito surveillance systems between outbreaks and provide technical support when outbreaks occur. 'We are in the process of making a strategic dengue prevention and control programme this year,' Dr Ehrenberg said. The problem is that dengue fever gets nothing like the political attention that is given to flu pandemic threats or the bird flu virus, particularly when outbreaks of bird flu are still occurring in Asia, including the mainland. 'We are concerned about a flu pandemic hence the concern about bird flu,' Dr Ehrenberg said. 'Dengue is rather localised; it will not spread like a flu pandemic.' However, most health officials only respond to dengue or malaria when an outbreak has already started and are not proactively seeking to prevent the disease. 'The WHO is working very hard with member states to address this issue,' Dr Ehrenberg said. The spread of dengue fever can be compared to that of the West Nile virus, which originated in Africa, and has spread throughout the Americas. It progressed from tropical zones to the United States and spread very quickly. 'People are moving more and when people move more they also transport diseases so you could actually carry disease from one part of the world to another,' Dr Ehrenberg said. 'The weather has changed dramatically. The glaciers are melting. You can see the changes from year to year. With the melting of the glaciers you also see the spread of disease.' Dr Ehrenberg said Singapore, however, was ahead of the game when it came to detecting such diseases. It had a very quick network that identified the patient and immediately alerted all the different sectors, including national parks and private businesses, he said, adding that Singapore had the problem of lots of people coming in from Malaysia and India and bringing the diseases with them. An example of Singapore's proactive approach was the discovery that bamboo water drainage outlets in the roofs of churches and other buildings were breeding sites for Aedes albopictus mosquitoes - the carriers of dengue. The government has now changed the construction code. Dr Omi highlighted other consequences of climate change for health, such as dysentery and malnutrition caused by floods and poor agricultural output. 'Some of the Pacific Islands like Tuvalu or Marshall Islands are already feeling the impact because of their low-lying areas,' Dr Omi said. 'That small change in sea level ... the seawater is seeping into the land, changing the salinity of the soil and changing the production of irrigated crops.' Mr Thompson said the WHO was planning to look into the impact climate change was having on the type, magnitude and distribution of diseases. Dr Chan said in short, climate change can exacerbate problems which are already huge. These problems are largely concentrated in the developing world and difficult to combat.