Singapore's dengue situation shows downward trend in 2008, 2009

Lynda Hong, Channel NewsAsia 27 Aug 09;

SINGAPORE : The dengue situation in Singapore has shown a downward trend in 2008 and 2009 - the first time in three decades. And this is despite a global surge in dengue cases.

Singapore registered 3,272 dengue cases up to August 22 this year - that's 15.3 per cent lower than the same period last year.

Singapore's National Environment Agency (NEA) said the country is on track to buck the cyclical increase in dengue cases, particularly during the warmer months from April to July.

This is the period when Singapore can typically register up to 150 cases a week.

But for April to July this year, Singapore had only about 100 cases a week.

The NEA said Singapore's dengue situation usually peaks after a 5 to 6 year cycle.

In 2007, it projected some 15,000 cases but Singapore only registered about 8,800 cases - down 20 per cent.

This downward trend continued last year when 7,000 cases were registered, much lower than the projected 20,000 cases.

This year, although the NEA has conducted 70 per cent more checks for mosquito breeding sites, the number detected has not increased significantly.

But it's still prepared to up the number of inspection officers by another 30 per cent to control the situation.

"We have successfully instituted and integrated a dengue control approach, using laboratory surveillance and field surveillance, and integrating these two components into a pre-emptive... kind structured regime to control dengue," said Tai Ji Choong, head of Operations, Environmental Health Department, NEA.

NEA said it will also work with other government agencies to manage the dengue situation in Singapore.

Of the four dengue strains, the dengue virus type 2 (Den-2) strain is the predominant dengue virus in Singapore. But the number of Den-3 cases has been increasing, especially in the West Coast area. - CNA /ls

Dengue cases on the slide
Straits Times 28 Aug 09;

THE dengue situation here is still under control, with the number of cases on a downward trend.

There is a 15 per cent decrease compared with the same period last year.

While the region is still seeing a spike, Singapore is bucking the trend, recording 3,272 cases so far this year, compared with 7,031 last year and 8,826 in 2007.

Singapore is now in the third year of a cycle that began in 2007. Each country has its own cycle. Dengue cases here usually follow a six- to seven-year cyclical trend, with each year's figures surpassing those of the year before.

In Malaysia, the number of dengue cases has surpassed that of the same period last year. Globally too, dengue cases have shot up by over two-fold compared with a decade ago.

The National Environment Agency (NEA) said its multi-pronged approach - surveillance and enforcement, community outreach and education, and research - has helped to minimise outbreaks of mosquito-borne diseases like dengue.

It will keep fine-tuning its approach of focusing its manpower in areas that are highly susceptible to outbreaks. This year, 21 areas scattered across the island were identified, based on past data and risk factors.

The NEA will analyse this year's dengue cases and see if it needs to widen the areas focused on. More people will be deployed if the need arises, such as if there is a switch in the dengue virus type, which will cause an increase in dengue cases.

Switches in the types of dengue - mainly Den-1 and the current predominant type, Den-2 - usually occur here every two to three years.

Mr Tai Ji Choong, head of operations at the NEA's environmental health department, said that the situation is now under control but there is still uncertainty over the dengue type switching.

'We need to balance resources with the situation. With the current resources, we are able to control the situation,' he said. 'At the same time, we can't reduce resources as we don't know when the switch in dengue virus type will come.'

The number of breedings detected in homes has also been dwindling since 2007, from 0.25 per 100 homes inspected to 0.13 this year.

JESSICA JAGANATHAN

Stricter malaria control in 13 workers' dorms
Regular pesticide sprays, netted screens required in dorms in 13 high-risk areas
Jessica Jaganathan, Straits Times 28 Aug 09;

DORMITORIES housing foreign workers in sites conducive to malaria mosquito breeding must now follow stricter measures to keep the problem at bay.

Interior and exterior walls must be sprayed regularly with pesticide, and windows must have netted screens to keep out mosquitoes. Weekly larvicidal oiling or spraying and night fogging must also be carried out by the management.

There are 13 dormitories in 13 'malaria-receptive areas' - in proximity to natural habitats like forested areas and coastal areas - around the island, including Dairy Farm Road and Punggol Point.

If any worker is suspected or confirmed to have acquired malaria locally, the employer must step up mosquito control and provide insect repellent or mosquito nets for workers who sleep on the premises.

The Ministry of Health is also conducting ad-hoc blood screening on all foreign workers living or working in these areas.

Dorm operators who fail to spray their dorms may face fines of $2,000.

The National Environment Agency (NEA) said that dorms built in the future should be fitted with netting on the windows, and carry out spraying of the walls.

Singapore is seeing its worst malaria outbreak in years, with 28 people infected here since early May.

The victims were living in, or had visited, one of three areas: Mandai/Sungei Kadut, Jurong Island or Sembawang. The latter two clusters are still active. Most of those infected were foreign workers living in dormitories.

Since it was told about the cases, NEA has waged an aggressive war against mosquito breeding, first in the affected areas, and then fanning out to the other vulnerable sites.

No company has been fined.

Malaria parasites are carried by the female Anopheles mosquitoes, which need to feed on blood to reproduce. When a mosquito bites an infected person, it picks up the parasite from his blood, and passes it to the next person it feeds on. Anopheles mosquitoes bite at night but are most active at dawn and dusk.

'The Anopheles mosquito does not breed in dorms but goes inside to bite people, so we are trying to keep the mosquitoes out,' said Mr Tai Ji Choong, head of operations at the NEA's environmental health department.

There are two species of Anopheles mosquitoes that transmit malaria here: Anopheles sundaicus and Anopheles maculatus.

Mr Tai said that more manpower may be committed to stamp out the malaria scourge, depending on the situation. He said that Singapore is still malaria-free as the virus has not become endemic here. The NEA is still studying if the outbreaks signal a more persistent trend or are one-off cases.

Singapore has been declared malaria-free since 1982, although it still sees between 100 and 300 cases a year. The majority are residents who become infected overseas. The last big outbreak was in 2006, when 13 people were infected locally.


Mozzie fight shows results
Dengue record shows downward trend, despite rise in cases worldwide
Ong Dai Lin, Straits Times 28 Aug 09;

EVERY five to six years, the number of dengue cases in Singapore rises to a peak, making up a typical cycle.

But for the first time since there were dengue records in 1960, the numbers have actually seen a downward trend in the middle of a cycle, instead of a steady rise.

The current dengue cycle started in 2006, with 3,126 cases, increasing to 8,826 in 2007.

But last year, the number dipped to 7,031 - and with just five months before this year ends, the number of dengue cases so far stands at 3,272.

And this number is unlikely to rise sharply for the remaining months, said Mr Tai Ji Choong, head of operations at the National Environment Agency's (NEA) Environmental Health Department.

This is because Singapore is approaching the end of the traditional peak period of dengue transmission from May to October. Cases are likely to remain low if there is no change in the predominant dengue strain.

The downward trend comes at a time where there is a worldwide trend of growth in dengue cases.

For example, in Malaysia, there have been 27,542 dengue cases this year as compared to 25,796 in 2008.

Mr Tai attributed Singapore's success to effective pre-emptive efforts by the Government and the public.

"After 2005, we reviewed our strategy and looked at the whole dengue situation and operations from the fundamental principles. We have successfully instituted an integrated dengue-control approach," he said.

NEA not only conducts inspections at premises and identifies high-risk dengue areas where more surveillance is needed but also conducts public education programmes to prevent mosquito breeding in homes.

It has also stepped up its number of inspections by 70 per cent so far this year as compared to the same timeframe last year, Fewer households have also been caught breeding mosquitoes.

The agency is also looking to increase its pool of environmental health offices from 750 to 1,000.

But the challenge of fighting dengue remains a tough one.

There are four strains of dengue, and any change in the predominant strain in Singapore can result in a huge increase in cases, said Mr Tai.

For instance, from March to May, there was a 30 per cent increase in the number of dengue cases caused by Den-3, a strain that had not been common in Singapore for about 10 years.

The result was that the population had a low immunity to it, and more people were vulnerable to infection.