The threat dengue fever poses to our city has been evident since the first locally transmitted outbreak struck down 20 victims in 2002. Two years on, however, this potential killer is still not being taken seriously enough. There have been no further outbreaks here, but the warning signs are growing. They point to this mosquito-borne disease representing a clear danger. Monthly indices recording the prevalence of the Aedes albopictus mosquito, which carries the disease, give rise to concerns. In April, seven areas recorded high levels. The figures for May, released yesterday, are even more worrying. They reveal that the average index is at a record level and that nine locations exceeded the 40 per cent threshold considered high-risk. Four areas hit the 50 per cent mark and one of them - Tai Wai - was more than 60 per cent. The situation has rightly been described by one health official as alarming. The fear is that there may be another outbreak and that the disease will gain a foothold in Hong Kong. It is, perhaps, surprising that this has not already happened. Our city would seem to offer the Aedes mosquito a perfect home. It loves our hot, wet, urban environment. The mosquito does not lack breeding grounds. It favours discarded lunch boxes, bottles and cans, empty tyres, blocked gutters, broken pots - anything which collects small amounts of water. These are all too easy to find in Hong Kong, even though there has been some improvement due to the cleanup campaign launched in response to Sars. Wiping out the Aedes mosquito will not be possible. But reducing its numbers to a relatively safe level should be easy to achieve. The key is to limit the breeding grounds. However, this will require an aggressive response from the government and a community-wide effort. We need to rekindle the spirit which helped defeat Sars. Since the dengue fever outbreak in 2002, the government has adopted various measures to limit the risks. Inspections of potential breeding grounds have been stepped up and there have been repeated calls for the public to guard against dengue fever. These have, no doubt, helped keep the disease at bay - and they are to be stepped up in the light of the latest index readings. However, the danger posed by dengue fever is still not sufficiently appreciated. A poll last year showed only 37 per cent of people take precautions to avoid mosquito bites, such as wearing repellent. And there appears to be a misguided perception that the risk exists only in rural areas. There is no room for complacency. Dengue fever, once known as 'break bone fever' is a painful and extremely unpleasant disease. There is no cure. That virtually all first-time victims recover offers little reassurance. A second infection can lead to a more serious form of the disease - and that can be fatal. Children are particularly at risk. Further evidence of our city's vulnerability can be seen in the prevalence of dengue fever in most parts of the region. There have been hundreds of cases in the Philippines this year, and thousands in Vietnam. A devastating outbreak in Indonesia claimed more than 250 lives. Hong Kong has, so far, managed to avoid joining the list of 100 countries where dengue fever is endemic. But only through a sustained and widespread effort will that situation be maintained. There is a need for a more intensive campaign to raise awareness and to motivate the whole community. A blitz should be launched on potential mosquito breeding grounds across Hong Kong - and not just in identified hot spots. This should have interdepartmental support. It is also worth considering a designated Sars-style cleaning day in which everyone is encouraged to rid their homes and workplaces of such sites. Dengue fever is avoidable. We all have a responsibility to ensure it does not get a grip in Hong Kong.