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Deadly Battle against Dengue in Southeast Asia

Updated On: Jun 12, 2007

Bird flu continues to be in the limelight as it became the main topic discussed at the APEC Health Ministers Meeting, June 6-8 in SydneyAustralia.

Pacific Rim health ministers promised on Friday to share samples of new bird flu strains in a cooperative effort to safeguard humans from the deadly virus. Indonesia is by far the hardest hit country with 79 human deaths or 80% of its victims. The H5N1 virus has killed at least 189 people and sickened 121 more worldwide.

Besides bird flu, the surge of dengue cases in Southeast Asia region is increasingly worrying. Singapore recorded a nearly 50 percent increase in dengue infections in the first 4 1/2 months of this year compared to the same period in 2006. Dengue cases reported from the start of January to May 12 rose to 1,488 - up from 993 in the corresponding period last year, according to the Health Ministry. Two men have died this year from dengue fever. Like several other Southeast Asian countries, Singapore reported a higher-than-usual number of dengue infections in 2005. At least 19 out of Singapore's 4.2 million people died in 2005 from the disease.

In Thailand, there has also been a 15 per cent spike in dengue fever cases so far this year. Dr Kamnuan Ungchusak, the director-general of the Disease Control Department's Bureau of Epidemiology, was quoted as saying by the Nation newspaper that the outbreak was 'abnormal' because it had spread to the mountainous northern regions, which are seldom hit. Health Ministry analyst Yaowapa Ganmeuan told The Straits Times that her office recorded 11,574 dengue patients from January to the end of last month, against 9,865 cases in the same period last year. The Health Ministry raised the alert last month when it noticed that Trat province, had reported dengue cases at a rate five times the national average.

In IndonesiaJakarta has been badly hit by dengue fever this year. So far, Jakarta has recorded 20,000 dengue cases and, separately, 62 deaths from the disease. This is a 10 per cent spike in the number of cases in the city since last year. In a move to fight the disease more aggressively, the city's administration plans to impose fines on those whose homes and buildings are breeding grounds for the Aedes mosquito, which carries the dengue virus.  Countrywide, official records showed that about 85,000 people had been infected with the dengue virus, and there had been 877 deaths. The number of fatalities in the January-May 2007 period in Central Java reached 230, which is higher than 217 recorded last year. Many of the victims died because they could not get to a hospital in time for treatment. Jakartaadministration’s initiative of mass clean-ups does not seem to be working because most Indonesians are still ignorant about how to prevent dengue.

The number of reported dengue cases in Malaysia was creeping up, with 994 infections reported last week compared with 980 a week earlier. The state of Selangor still tops the list with 338 cases, followed by Kuala Lumpur with 127 cases and Kelantan with 80. The Malaysian government has proposed that Singapore and Malaysia look into joint research to better understand the different strains of the Aedes mosquito-borne virus, since dengue fever is flaring up again to near-epidemic levels in both countries. Malaysian health officials are also trying to rope in domestic maids to eradicate mosquito breeding grounds at home.

In the Philippines, penalties are imposed on those breaking a dengue-prevention ordinance, particularly in poor areas. The community passed an anti-dengue ordinance last year after a sharp rise in the disease in shanty areas. Dengue cases in Quezon City, which has two million residents, hit epidemic levels last year - 2,253 people were infected with the virus, a 30 per cent rise over 2005. Countrywide, the Department of Health logged 35,758 cases and 368 deaths, compared with 33,504 cases and 397 deaths in 2005. A decade ago, the country started a national dengue prevention programme to control the spread of the disease. Many local governments strengthen this with their own initiatives. Still, Quezon City's health chief Antonieta Inumerable believes stronger measures are needed. He said: 'If you are poor and your stomach is empty, most do not make the extra effort.'

Recent changes in Aedes mosquitoes' behaviour suggest they are adapting, making the anti-dengue mission harder, therefore a review of current approaches may be needed, said Carl Baptista, a pest management expert. The mosquitoes are now able to rest and deposit eggs where they see fit, both indoors and outdoors. NEA's strategy of 'search and destroy' and also 'source reduction' - the removal of stagnant water bodies - has been largely successful. But with the rise in dengue cases, a review of these approaches may be needed. Recent studies conducted in Singapore have shown that thermal fogging has little effect on the wild mosquito population when conducted between the hours of 9am and 5pm. A Straits Times reader said that in an US experiment, it was found that less than 4 per cent of mosquitoes were killed with fogging. New strategies suggested include newer water-based pesticides that kill mosquitoes more easily. In short, mosquitoes should be killed at all stages of the life cycle.

Interestingly, researchers working for the Indonesian Mosquito Control Association have discovered that 30 percent of male Aedes aegypti mosquitoes have now also become a vector for the dengue virus. The discovery has changed the long-held perception that only female Aedes aegypti mosquitoes carry the virus and led to the conclusion that the risk of the disease becoming endemic in Indonesia has increased, Dr Tri Baskoro T Satoto, the association`s secretary general. This discovery will be studied further to establish the pattern of the dengue virus` spread in the long term so that the right anticipatory steps can be taken.

Some sources also reported that the increase of dengue cases in the region is partly caused by global warming. Indeed, warmer climate leads to more frequent mosquito breeding.  A group of Indonesian researchers confirmed a new strain of virus, which was believed to be mutated due to warmer temperature. However, this has been denied by the WHO. The Asian Development Bank developed a model suggesting that dengue might rise three-fold in Indonesia due to climate change.

The spread of dengue has also accelerated in recent years due to increasing urbanisation and travel or migration within the region, experts say. Efforts to develop a vaccine are proving difficult because dengue can be caused by four viruses. So the only real method to fight the disease currently is to eliminate likely breeding spots for mosquitos from discarded tyres to plant pots. The most effective way of fighting the outbreak is to prevent from the first place rather than react by curative action.  (11 June 2007)

Sources:

Singapore Sees Rise in Dengue Infections  (AP, 21 May 2007)

Fewer dengue cases reported here last week (Straits Times, 6 Jun 2007)

Thailand: Climate change partly to blame, says expert  (Straits Times, 8 Jun 2007)

Indonesia: Fines, jail planned for breeding mosquitoes, Straits Times, Jun 8, 2007

Malaysia: KL calls for research cooperation with S'pore (Straits Times, 8 Jun 2007)

PhilippinesBattle to keep shanty towns clean (Straits Times, 8 Jun 2007)

Clearing the fog in the war against dengue (Straits Times, 9 Jun 2007)

New methods and strategy needed to curb mosquitoes (Straits Times, 6 Jun 2007_

Southeast Asia battles dengue surge amid climate fears (Straits Times/ Reuters, 10 Jun 2007)

City's dengue fumigation campaign 'a total flop' (Jakarta Post, 10 Jun 2007)

Dengue kills 230 in past five months in C Java  (Antara, 8 Jun 2007)

Research finds 30% of male aedes aegypti mosquitos carry dengue virus (Antara, 20 May 2007)