10 new cases of chikungunya fever, 8 at Kranji Way cluster

Channel NewsAsia 8 Aug 08;

SINGAPORE: The Ministry of Health (MOH) says there are eight additional cases of chikungunya fever involving six foreign workers and two locals working at Kranji Way.

Five of the foreign workers are working and residing at the site in Kranji Way, while the remaining worker commutes daily from Malaysia to work. The total number of cases linked to Kranji Way currently stands at 28.

National Environment Agency (NEA) officers have been conducting intensive mosquito control operations within the vicinity of the cases' workplace and residences, and the areas that they frequent.

More than 28 premises have been inspected in the Kranji Way area and a total of 16 premises were found breeding the Aedes mosquito.

Outdoor and indoor fogging of insecticide has been carried out for all the premises checked.

MOH says this intensive operation to seek out and remove any mosquito-breeding habitats will continue.

Residents and premises owners in the vicinity of Kranji Way have all been advised to check their premises daily to remove any stagnant water that may breed mosquitoes.

The ministry has also been notified of two new cases of chikungunya fever not related to the Kranji Way cluster.

The first case involved a 27-year-old housewife who stays at Woodlands Street 81. She developed symptoms on Monday, sought outpatient treatment at a medical clinic and has since recovered.

She has no recent history of travel overseas and her movements were largely confined to her residence and nearby places. MOH has conducted active case detection among her seven household contacts. None was tested positive for chikungunya virus.

The second case involved a foreign worker, a 40-year-old Chinese national, who works and resides at Sungei Kadut Street 1. He developed symptoms on 4 August and was admitted to the Communicable Diseases Centre three days later.

MOH says he has no recent history of travel overseas and his movements were largely confined to his workplace and nearby places.

MOH has conducted active case detection among his 38 co-workers at his workplace. None was tested positive for chikungunya virus.

NEA is carrying out vector control operations in the premises around the cases' residences, including the common and public areas.

Areas where the cases frequented are also being inspected for mosquito breeding.

So far, five premises in the vicinity of the case residing at Woodlands St 81 were found breeding the Aedes mosquito.

NEA's checks in the respective areas are continuing.

95 cases of chikungunya fever were notified to MOH so far this year.

- 938LIVE.

10 more with chikungunya
Lee Hui Chieh, Straits Times 9 Aug 08;

TEN more people have caught chikungunya here, the Health Ministry said yesterday.

They include eight workers from Kranji Way (see other report 'Kranji fogged to control outbreak'), a foreign worker living and working at a factory in Sungei Kadut Street 1, and a housewife in Woodlands Street 81.

The Sungei Kadut worker, a 40-year-old Chinese national, fell ill on Monday and was admitted to the Communicable Disease Centre (CDC) three days later.

The housewife, 27, fell ill also on Monday, but has since recovered after seeing a doctor.

Health officers have screened the worker's 38 colleagues, as well as the seven people living with the housewife. All have been found clear.

The National Environment Agency (NEA), after blitzing the areas surrounding the affected factory and home, have so far found five premises near the housewife's home breeding the Aedes mosquito which transmits the chikungunya virus.

All of the latest patients probably contracted the mosquito-borne, dengue-like disease while here.

This brings this year's total tally of those infected while in Singapore to 49. A further 46 caught the disease overseas.

This is the first year in which the infection has spread locally. Thirteen people who became ill in 2006 and last year were infected abroad.

The growth in the number of cases here follows a rising trend in other countries, noted the CDC's clinical director, Associate Professor Leo Yee Sin.

For example, Malaysia has already chalked up a record high of 136 chikungunya patients this year, up from fewer than 100 patients for the whole of last year.

Prof Leo added that Singapore was at high risk as the Aedes mosquito flourishes here. Also, the people have no immunity to the disease, and many travel overseas or visit from abroad.

Investigations are still ongoing to see if the local cases here are linked, a Health Ministry spokesman said yesterday.

She urged travellers to areas which have had chikungunya outbreaks, such as Malaysia, Indonesia and India, to wear long-sleeved shirts and long pants when outdoors and to use insect repellent.

Singapore residents should take steps to prevent mosquito breeding, she said.

Kranji fogged to control outbreak
Chikungunya hits 28 in area; health officers destroy sites found to be breeding mosquitoes
Lee Hui Chieh, Straits Times 9 Aug 08;

IT WOULD have been a 10-minute walk from his Kranji workplace to a nearby clinic - in normal conditions.

But Mr T. Shankar took 45 minutes to hobble there, nursing a 39.5 deg C fever and doubled over in pain from swollen ankles, knees, wrists and fingers.

The Chennai native, 32, said: 'It was so painful that I couldn't sit down, stand up, lie down or walk. The soles of my feet were on fire.'

He was among 28 infected in a chikungunya outbreak at Kranji Way, which has since become the largest cluster of victims of the mosquito- borne disease here.

Before this, the first and largest outbreak in January had infected 13 people living or working in Little India.

In the Kranji outbreak, two foreign workers from a firm making building materials and a Singaporean making a delivery there were the first three victims reported at the end of last month.

Health officers, who screened 282 workers in the area, found 15 more patients from the company, including Mr Shankar, and two more working at a storage yard next door.

In the past three days, eight more workers from the company have fallen ill and been admitted to the Communicable Disease Centre (CDC), the Health Ministry said yesterday.

The group comprises two Singaporeans and a Malaysian, as well as two Bangladeshis and three Indian nationals who live on the company's grounds.

Officers from the National Environment Agency (NEA) checked more than 28 factories in the area, fogged their indoor and outdoor areas and destroyed mosquito-breeding sites in 16 of them.

It was an alert general practitioner who raised the alarm in the Kranji outbreak. Dr Yip Mang Meng's suspicions were aroused when five men limped into his Kranji Road clinic one after another, all with high fevers and severe joint pains.

They each took two to three minutes just to stagger from the waiting area into his consultation room, he said.

Dr Yip, 60, said: 'It was like they were suffering from gout and arthritis. And they couldn't grip with their hands because it was too painful.'

He sent their blood samples to be tested for dengue, malaria and chikungunya. It turned out that the lab he had sent them to did not do tests for chikungunya, though the blood samples were negative for dengue and malaria.

The next day, July 31, two more patients limped in with the same symptoms. Dr Yip sent their blood samples to the NEA's Environmental Health Institute, which has been running tests on blood samples collected by health officers. When those came back positive, he notified the Health Ministry.

No cure exists for the disease, which usually lasts three to 10 days and then goes away. It is rarely fatal.

Being told this by a doctor came as a huge relief to Mr Shankar. His fever subsided after three days, but returned after a week. The joint pains lingered.

He found out about chikungunya only after CDC health officers screened him on the day his fever came back. He was hospitalised for four days.

'I wouldn't wish for anybody to suffer this pain,' he said.

DAEDALUS: TECHNOLOGICAL TRIUMPHS AND CHALLENGES
What endemic chikungunya?
Andy Ho, Straits Times 9 Aug08;

BEFORE last week, there had been 51 chikungunya cases detected here since January. But just this week alone, a further 18 cases have popped up.

First identified in 1952 in an outbreak along the border between Tanganyika and Mozambique, the illness resembles dengue, with high fever and serious joint pains among its symptoms. The haemorrhagic illness common with dengue is, however, rare with chikungunya, which is thus usually non-fatal.

When it first appeared in Singapore in 2006, its three cases - as well as the 10 recorded last year - were all imported. In January, however, local transmission was for the first time definitively detected among 13 people living near Tekka Mall.

The local cases have derived mainly from infected foreign workers from the Indian subcontinent, carriers who then became index cases here. India, in turn, gets the bug from Africa.

Genomic studies reveal that the virus originated more than a millennium ago in West Africa, then spread to other parts of Africa before invading Asia and circulating in the Indian Ocean region.

The last major epidemic began in Kenya in 2004, spread to several Indian Ocean islands early in 2005, where the outbreaks were massive, before jumping to India, and thence to Singapore.

How it is transmitted differs geographically. In Africa, it is largely a rural phenomenon, with the Aedes mosquito spreading the virus from animal reservoirs, probably monkeys, to humans. In Asia, it is transmitted in crowded urban settings from human to human by the Aedes Aegypti. Recently, one mutation of the virus that arose in different parts of the world independently and separately has enabled the bug to also ride on the Aedes Albopictus, which attacks only humans, not animals.

The local transmissions involve three different strains. But the bug is unlikely to have mutated from one into another and then yet another strain since just January. So the authorities think the local cases are not linked to one another. Instead, they must have come from different, presumably imported, index cases. That is, the virus is not endemic - yet.

Here is the good news: Chikungunya may well remain non-endemic for a long time to come if patterns for its outbreaks outside Africa stay the same.

Unlike most insect-borne viruses, including dengue, chikungunya seems to go into long periods of quiescence after an outbreak before it re-emerges in another epidemic. In Malaysia, it reappeared after its 1998/99 outbreak only in 2006. Indonesia had a 20-year hiatus after an outbreak in 1985. India was free from 1971 to 2005, and it was all quiet in the Democratic Republic of the Congo for 39 years, until 2004.

This is quite significant. Given the high birth rates in these countries, most of their young would have no immunity to the bug, so epidemics should logically be more, not less, likely. The reason they are not might be that the dengue and chikungunya viruses are genetically very different, though they cause similar illnesses.

The dengue virus is a Flavivirus while the chikungunya is an Alphavirus. The former is able to break free of its animal reservoir while chikungunya has not - and finds it hard to. If so, non-African outbreaks will eventually still have to come from animal reservoirs in Africa.

Of course, cheap air travel and the flood of migrant workers have helped the virus bridge the vast distance from Africa to Singapore. But the virus is unlikely to make its home here because it needs to find not just a hospitable animal reservoir but also animal 'amplifiers' as well.

Delinked from its animal reservoirs, the dengue virus just had to adapt to locally available mosquitoes before it spread like wildfire among humans. In contrast, the chikungunya virus may have to jump through many other hoops.

Experts think these are like those faced by another Alphavirus found in rodents. The Culex mosquito spreads this virus among rodents. For it to spill over to humans, it must first go through horses, which amplify its virulence. Hence its name: Venezuelan equine encephalomyelitis virus.

But for it to run riot among horses, the virus must acquire a very specific mutation so it can infect the Aedes mosquito, which is able to transmit the virus among horses and from horse to man. (The subtype of the virus in rodents can use only Culex mosquitoes, whereas the subtype in horses can use only Aedes mosquitoes.)

But acquiring a very specific mutation is an event of very low probability. Moreover, that mutation cannot be 'kept' once an epidemic burns out. That specific mutation must be reacquired by the bug before it can trigger off another epidemic.

If the chikungunya virus is like this cousin Alphavirus, then it would still be linked to its animal reservoirs and yet-identified animal amplifiers. And it will need to reacquire, each time, precisely that very same mutation that enabled it to spread around the Indian Ocean region in 2005/06 and to Italy last year.

That is a very tall order indeed. So it is unlikely to become endemic here. If our mosquito-busting efforts stop the virus in its tracks quickly, it might just go quiescent - hopefully for decades - while it tries to reacquire that dastardly mutation.