COLOMBO, 9 July 2009 (IRIN) - Sri Lankan health authorities are battling to contain one of the worst dengue outbreaks in years - more than 15,500 cases and 168 deaths have been reported since January, according to the Ministry of Health.

June was the worst month, with 6,600 cases of the mosquito-borne infection.

In 2004, the last major outbreak, 88 people died out of 15,000 reported infections.

Health officials were first alerted to a possible outbreak when the number of reported cases spiked between January and April, with more than 2,800 cases and seven deaths. The virus then spread even faster between April and June when 11,655 cases were noted.

Health officials, however, are unsure as to the cause of this latest outbreak.

"Most countries with established dengue transmission experience major epidemics approximately every four years and we do not understand why this is so," a new report by the Ministry of Health's epidemiology unit, Dengue Control in Sri Lanka - a Snapshot, stated.

Some suggest the virus may have mutated or a non-native strain had become active, but there is insufficient data to support this theory, the report maintains. Already the virus has spread to areas of the island that had not seen unusually high prevalence rates before.

"There are a large number of cases in the hill country [central part of the country], where we have not seen so many cases in the past," Palitha Mahipala, deputy director of public health at the health ministry, told IRIN.

The central hill district of Kandy is the worst affected, with about 2,200 cases.

The coastal districts of Colombo, Gampaha and Kalutara, which have been susceptible in the past, have also recorded a high rate of infection and deaths.

According to health experts, more than half the sufferers are women and children.

"The mosquito is active during daylight hours and also inside homes, where women and children stay during the day," Paba Palihawadana, head of the epidemiology unit at the ministry, said.

Clean-up campaign

The government has taken steps to contain its spread, including public awareness campaigns and clean-up operations. At the same time, it is trying to import a bacteria, Bacillus Thuringiensis Israelensis or BTI, which can kill the mosquito at the larvae stage.

Doctors and prevention agencies such as the National Dengue Prevention Unit are also undertaking outdoor spraying campaigns.

"Most of the breeding areas are man-made and can be eliminated. The public needs to be more vigilant and take care of their gardens as well as inside their homes and offices," Palihawadana said.

Tyres, discarded canisters and even flower pots with excess water can all serve as deadly breeding grounds, she said.

"The larvae will mature within 10 days, so there needs to be constant vigilance," she said. "We shouldn't wait until an epidemic breaks out to do clean-ups."

According to the epidemiology unit, this latest outbreak is unlikely to be the last, making public awareness all the more important until a possible vaccine is developed.

Although it was not feasible to eradicate dengue from Sri Lanka in the near future, a well-organised vector control programme could reduce the number of infections, the report stated.

"In addition to focusing on mosquito control, dengue prevention efforts should also emphasise accurate early detection and treatment," it stated.

According to the World Health Organization (WHO), the incidence of dengue has grown dramatically. Some 2.5 billion people - two fifths of the world's population - are now at risk. It estimates there may be 50 million dengue infections worldwide every year.

As of 30 June, Indonesia had reported 67,719 cases and 511 deaths, while Thailand had recorded 3,496 cases and five deaths as of April.

ap/ds/mw

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