NEA concerned about rise in rare Type 3 Dengue cases

938LIVE Channel NewsAsia 18 Mar 09;

SINGAPORE: The National Environment Agency (NEA) is concerned that a randomly-occurring type of the dengue virus has recently shown up in greater numbers in one area.

Seven cases of Type 3 Dengue infection were detected in Little India in January, up from zero cases in November last year.

NEA says the virus type has "high epidemic potential" because Singaporeans are known to have low immunity.

NEA's Head of Environmental Health Institute, Dr Ng Lee Ching, explains: "Dengue 3 is not very common in Singapore for the past decade. So our immunity level in the population is very low towards Dengue 3. Which means if Dengue 3 spreads, the population will be very susceptible to getting dengue. We also know that overseas, in America and in Southeast Asia, Dengue 3 has caused huge outbreaks."

NEA says it immediately deployed officers to Little India to locate and destroy mosquito breeding grounds. And the number of Type 3 infections there dropped back to zero in February.

As a precaution, Head of Operations for the Environmental Health Department at NEA, Tai Ji Choong, said that officers are permanently stationed in the two areas.

He said: "Actually we put in a permanent team of officers and also the pest control operators. Actually they're roving around the area to actually do source reduction, to remove and destroy breeding habitats and at the same time check difficult areas such as roof gutters for breeding."

NEA says it has also been able to contain the rise in Type 1 Dengue infections reported in Woodlands, Joo Chiat and the Southwest District.

The number of cases in these areas rose over the new year but fell last month.

Type 1 and 2 Dengue are the more common strains occurring in Singapore, while Type 4 is rare.

NEA currently has 750 pest control officers fanned out across Singapore to check and destroy mosquito breeding areas.

The agency says it plans to hire another 250 officers this year to increase its surveillance.- 938LIVE.

Rare dengue type on the rise in Singapore
Alert for Den-3 virus, which can cause a major outbreak if not contained
Jessica Jaganathan, Straits Times 19 Mar 09;

DENGUE numbers are down but public health officers are on high alert.

The reason: An unfamiliar dengue virus has emerged which has the potential to spark a major outbreak.

Though officials said on Tuesday that they have managed to contain the Dengue-3 virus for now, they are still keeping a close watch on it, as it has not been seen here commonly for some 10 years.

With low immunity to Den-3 in the population, people are more vulnerable to infection.

Officials are concerned because cases increased more than three times last November and December, and were found mainly in two areas, sparking fears that transmissions were high and could spread.

There are four types of the dengue virus, and people who have been infected by any one type are immune to it for life. But that still means that an individual can get dengue fever up to four times.

In Singapore, two main types of the dengue virus have circulated in the past 10 years: Dengue-1 and Dengue-2, with the latter now predominant.

Past data shows that outbreaks in 2005 and 2007 were preceded by a switch in the predominant type of dengue virus.

In the past few months, researchers from the National Environment Agency (NEA) found that the third type, Den-3, had emerged in greater numbers in Little India and Geylang.

On average, Den-3 makes up about 5 per cent of all dengue cases here. But in November and December last year, it increased to more than 17 per cent.

Although the numbers dropped back to 5 per cent last month, after NEA officers went to war against mosquitoes in the hot spots, the authorities are still watchful. Because of the rarity of Den-3 here, Singaporeans' immunity to it is very low, said Dr Ng Lee Ching, head of the NEA's Environmental Health Institute.

Alarm bells went off as well, when infections clustered in two areas, Little India and Geylang, for two consecutive months.

'We straightaway launched our resources in these areas as we didn't want Den-3 to have a launching pad to spring out to the rest of Singapore,' said Mr Tai Ji Choong, head of operations at the NEA's environmental health department.

If it did spread, NEA officials feared a worse outbreak than in 2005, which infected more than 14,000 Singaporeans and caused 25 fatalities, he said.

They went to work on the main lines of defence that have been successful in reducing numbers in the past: eliminate breeding spots and rely on the research team's laboratory work to pinpoint where the dengue type was dominant.

Officers are now posted permanently in the two areas to wipe out breeding areas and two additional pest control teams have been deployed to check tricky spots like roof gutters for breeding, he said.

They are also keeping watch on neighbourhoods in the south-west, like Bukit Batok and Jurong as well as Woodlands and Joo Chiat, where there has been a sharp increase of 10 per cent to 20 per cent in Dengue-1 cases over this year.

The numbers fell last month, said Mr Tai, but the possibility of a new outbreak remains.

With warmer weather expected, NEA officers, together with other agencies, are stepping up efforts to reduce and remove possible mosquito breeding sites.

The World Health Organisation (WHO) warned last week that 1.8 billion people in the Asia-Pacific region are at risk of being infected with dengue, which has been gaining in South-east Asia.

Rare dengue cases: Doctors on alert
Cases of unfamiliar Den-3 type rising in Little India, Geylang
Jessica Jaganathan, Straits Times 20 Mar 09;
DOCTORS in Little India and Geylang are taking no chances and are ordering blood tests when patients show up with signs of dengue, now that a new threat has emerged in those areas.

More patients are turning up with a fever, headache and joint or muscular pains at Dr Mohamed Ghazali's clinic in Little India.

He said: 'It's difficult to tell those with influenza, chikungunya and dengue apart as they mostly have the same symptoms. So now I'm getting all of them with such symptoms to go for a blood test early.'

Dengue test results are back within a day.

GPs have received circulars from the Ministry of Health recently after a higher number of dengue patients in Little India and Geylang were found to have an unfamiliar variant of the dengue virus - Dengue-3 - which has the potential to spark a major outbreak.

Den-3 is one of four types of the dengue virus, but Singaporeans are more vulnerable to it because of their low immunity to it.

On average, Den-3 makes up about 5 per cent of all dengue cases here. But in November and December last year, the figure increased to more than 17 per cent.

Also worrying is the fact that the cases were concentrated in these two areas for two consecutive months, where previously, Den-3 was spread across the island.

If it takes root in these areas, they could provide 'a launching pad to spring out into the rest of Singapore', a National Environment Agency (NEA) official had said. The fear is that an outbreak could occur that is far worse than the one in 2005, during which more than 14,000 people were infected and 25 of them died.

For now, NEA believes it has contained the situation by deploying extra manpower to eliminate mosquito breeding spots where the Den-3 virus is dominant.

Residents in those areas, like provision shop owner Chew Yang Koo, 53, are checking and cleaning possible breeding areas like pails and flower pots more frequently.

And when it rains, he makes an extra effort to ensure no puddles are left overnight which would allow mosquitoes to breed at his shop in Race Course Road.

Over in Geylang, Dr Joyce Liang has confirmed three cases of dengue this week alone, while in the past, she would hardly see anyone with dengue in a month.

'I'm being extra vigilant now especially in the Geylang area where you have a lot of movement of people and a high number of foreigners,' she added.

Health officials are unable to confirm where Den-3 originated from, but going by available data, they say the genes of the virus indicate the cases here are related to those in Thailand, Philippines, Indonesia and Sri Lanka.

Of the 120 dengue patients from November to February in the two areas, 95 were foreigners.

Although people who get one type of dengue develop lifelong immunity to that virus, studies have shown that subsequent infection with a different type makes a person more susceptible to the more severe dengue haemorrhagic fever.

The World Health Organisation's regional adviser in this field, Dr John Ehrenberg, speaks from experience because his wife has had dengue fever twice.

In town for the first Asia-Pacific dengue workshop this week, he stressed the importance of countries in the region sharing data and research in order to tackle dengue epidemics well.

Currently, there are still gaps in many countries, such as poor information flow between the field officers and policymakers, he said.

And instead of reacting when an outbreak strikes, money and resources should be spent in between epidemics to minimise the impact of the next outbreak, he added.

WHO estimates the average annual cost of dengue cases in Asia to be about $245 million, nearly half the global figure.