Singapore authorities on dengue alert with onset of El Nino phenomenon

Imelda Saad Channel NewsAsia 26 Mar 10;

SINGAPORE : Singapore authorities are on the alert for a rise in the number of dengue cases here with the onset of the El Nino phenomenon.

The Aedes mosquito breeds faster and the rate of infection is higher during warmer months.

The good news is that Singapore is seeing a downward trend in dengue cases. So far, the damage from the Aedes mosquitoes has been kept in check.

But the situation may change when the weather gets warmer, due to the El Nino phenomenon.

The full impact of Singapore's hottest month in February is likely to be felt in the middle of next month.

The last time there was an El Nino phenomenon in 1998, there was a worldwide resurgence in dengue. In Singapore, case numbers peaked at more than 5,000 during that year.

Another challenge is areas with emerging Types 1, 3 and 4 of dengue circulating in Singapore. These are the lesser predominant types of dengue here.

The dominant dengue type currently circulating in Singapore is Type 2.

Ironically, Singapore's success in keeping dengue cases low means that fewer people have built up immunity against the disease.

Tai Ji Choong, head operations, National Environment Agency, said: "Cases are likely to increase slightly, and of course we are approaching the warmer months of the year, so we expect (that during) these next few months, cases are likely to rise".

The good news is that Singapore's dengue prevention strategy has proven to be effective. Over the past three years, the number of cases has gone down consecutively. For example, last year, there were about 4,500 cases, about 40 per cent fewer compared to 2008.

And from January till the third week of March this year, there were about 980 dengue cases - down about 30 per cent compared to the same period last year.

This downward trend means Singapore has managed to break the cycle of dengue outbreaks.

Typically, dengue cases spike every five to six years.

The last peak was in 2004 and 2005 when there were 9,459 and 14,209 cases respectively. The next peak would be in 2011.

Based on this cycle, it is estimated that Singapore could expect to see about 49,000 dengue cases in 2011. But this is now unlikely to happen.

The NEA is hopeful that if a new type of dengue does not emerge in Singapore, cases could be capped at levels seen in 2009 and 2008.

An inter-agency task force has started its annual Intensive Source Reduction Exercise, targeting dengue hotspots and potential breeding grounds.

The NEA is also keeping its eye on areas with emerging cases of the less dominant dengue types.

It has expanded its network of GPs to take blood samples from patients.

Mr Tai said: "Now we want to prevent another serotype from getting predominant in Singapore. We are working very closely with the GPs, the hospitals and clinics to encourage them to send samples to us for blood testing, so we are able to know what are the serotypes that are circulating in Singapore, so that we can deploy resources over there to control the spread of these serotypes."

The NEA has also reminded the community to remain vigilant.

Mr Tai said: "We know that mosquitoes can breed anywhere, whether in public places or in homes. If everybody cooperates and is alert about stagnant water, I think together we can control the mosquito population and control the dengue situation in Singapore".

As with previous years, households account for the most number of breeding sites detected.

The most common places where mosquitoes are found to be breeding are domestic containers, flower pot plates and discarded receptacles. - CNA/ms

As the weather warms up, the war on dengue heats up
Alicia Wong, Today Online 27 Mar 10;

SINGAPORE - The continuing warm weather and the increasing likelihood of another dengue type overtaking the current one, has put the National Environment Agency (NEA) on alert. Highlighting these as factors for an anticipated spike in dengue cases, NEA said it has started working to increase its network of General Practitioners.

When cases of non-predominant dengue type are found during random nationwide sampling, the NEA's Environmental Health Institute will get GPs in the affected areas to submit more blood samples so it can narrow down the locations affected, and send officers to tackle the problem.

There are four dengue types: 1, 2, 3, and 4. Dengue 2 has been predominant here since 2007 and hence, most people would have immunity only to this.

Data shows the predominant dengue type changes every two to three years. After a change, the number of cases usually spikes. This was seen in 2007, when there was 8,826 cases, compared to 3,126 cases in 2006 when Dengue 1 was predominant.

Some areas found to have two or more Dengue 1, 3 or 4 cases this year include Woodlands, Veerasamy Road and Richards Avenue. NEA's environmental health department's head of operations. Mr Tai Ji Choong, said if there is no type change, the number of cases this year could hold at 2008 and 2009 levels.

There were 7,031 cases in 2008 and 4,497 last year. These figures bucked the six- to seven-year dengue cycle, where the number of cases rises until it peaks during the last year of the cycle. The current cycle which started in 2006 could theoretically have peaked in 2011 with a projected 49,200 cases.

But instead, there has been a downward trend, attributed to NEA's surveillance, enforcement and education efforts. The agency continues to urge the public to exercise vigilance to keep homes free of stagnant water.

Mr Tai also noted that the current El Nino conditions are expected to persist until end-April before gradually weakening. Singapore is also approaching the warmer months of the year, and cases are expected to rise, he said. Typically, cases start increasing from mid-April to June.

The last El Nino was in 2004 to 2005, which saw 9,459 and 14,209 dengue cases respectively. 2005 was also the peak of the dengue cycle. So far this year, there have been 978 cases as of March 20, about 30 per cent fewer than in the same period last year. Alicia Wong

Dengue alert
NEA watching for spike in cases here as less common strain surfaces
Karamjit Kaur Straits Times 27 Mar 10;

SINGAPORE is on alert for a possible spike in cases of dengue fever, especially for people coming down with a less common type of the virus.

The current warm spell, brought on by the El Nino weather phenomenon, is partly to blame, the National Environment Agency (NEA) said yesterday.

Though mosquitoes need stagnant water to breed, it is dry weather that not only accelerates breeding, but also makes the insects infective faster.

While there is no reason for alarm, the authority is on alert because there is evidence that Dengue Type 1, 3 and 4 may be becoming more rampant, said the head of operations at NEA's environmental health department, Mr Tai Ji Choong.

Random blood samples taken from those who caught the disease this year showed that cases of the less common viruses have surfaced in parts of Woodlands, as well as in Serangoon Road and Serangoon North.

In the last few years, Type 2 has been the more common dengue strain in Singapore, said Mr Tai.

But with the cycle usually changing every two to three years, experts believe another shift is imminent.

Although no one virus type is more dangerous than the other, the problem is that fewer people here are immune to Type 1, 3 and 4, said Mr Tai.

A person who has caught one dengue type has lifelong immunity to it, but not to the others.

The key to battling the potential threat is to ensure that the less dominant viruses do not spread and are quickly nipped in the bud when they occur.

The NEA is seeking the cooperation of the medical community for this.

Mr Tai said that the NEA will be working very closely with the hospitals and clinics to encourage them to send blood samples to the NEA for testing.

This will help the NEA determine what dengue type is out there.

'The more samples we receive, the more we are able to know what the situation is so that we can quickly deploy resources to control the spread,' he added.

As for the public, NEA's appeal is the same: Get rid of stagnant water.

Mr Tai said: 'If we are able to contain the situation and there is no change in the predominant dengue type, all things being equal... I think we will be able to further contain the problem this year... We hope this year will be as good as 2008 and 2009.'

Last year, a total of 4,498 people caught the disease, down from 7,031 in 2008 and 8,826 the year before that.

As at the end of last week, 978 cases have been reported so far this year, a 28.4 per cent drop over the same period last year.

By contrast, in nearby countries such as Malaysia for example, cases have been on the rise.

Singapore has done well to contain the dengue situation so far, said the NEA.

But with the warmer months approaching and El Nino expected to persist, more cases will be expected in the coming months, said Mr Tai, adding that the number typically peaks in June and July.

Apart from working with hospitals and clinics, NEA will continue to partner various government agencies, as well as town councils and industry bodies, to contain the mosquito situation.

After the last peak hit in 2004 and 2005, the agency went into full swing with a new action plan, which among other things, laid down how often each home, hawker centre or school should be checked.

Since then, regular meetings have been held with representatives of 26 government agencies and other partners to share information and keep tabs on what is happening on the ground.

Last year, more than 4.3 million inspections were carried out, compared to about 2.8 million in 2008.

The checks led to 16,977 breeding habitats detected last year, down from the 20,263 that were discovered the year before that.

It is good news but the work continues, said Mr Tai, noting: 'We know that mosquitoes can breed anywhere; whether in public places or at home. If everybody cooperates... I think together we can control the mosquito population and control dengue in Singapore.'

Clinical director of the Communicable Disease Centre Leo Yee Sin said: 'Should the outbreak (if it happens) be of the same scale as in 2004 to 2005, we are now better prepared owing to more dengue research after the earlier outbreaks leading to better understanding of disease management.'