Vigilance against dengue urged due to increase in mosquito population, slightly warmer than usual weather

The Aedes mosquito population has doubled in the first 10 months of this year.
The Aedes mosquito population has doubled in the first 10 months of this year. PHOTO: ST FILE

SINGAPORE - The number of dengue cases in the first 10 months of 2015 has dropped by about half compared to the same period last year, but the Aedes mosquito population has doubled.

Add to that weather that is slightly warmer than usual due to the El Nino phenomenon - conditions which support faster breeding and maturation cycles for the mosquito and shorten incubation periods for the dengue virus - and a surge in dengue cases could occur, the National Environment Agency (NEA) said.

In a statement on Wednesday (Dec 2), the agency urged people to stay vigilant and take measures to suppress the Aedes mosquito population.

It said that as of Oct 31 this year, 8,520 dengue cases have been reported. That figure is about 48.6 per cent lower than last year's figure of 16,569 cases in the same period. However, the Aedes mosquito population in October is double that of October 2014.

The NEA added that the proportion of cases due to the DENV-2 serotype has increased, now accounting for half of all dengue cases in Singapore. The DENV-1 serotype had accounted for most of the dengue cases here since March 2013.

This change in the main circulating dengue virus could be an early indicator of a future dengue outbreak unless measures are taken to reduce the number of Aedes mosquitoes, the agency said.

Historically, a change in dengue serotype is usually followed by a spike in dengue cases. The last serotype switch, from DENV-2 to DENV-1 in March 2013, saw a sharp dengue outbreak that year. That outbreak recorded a historic high of 22,170 cases.

Now the serotype 2 cases have crept up again, an increase from about 44 per cent in mid-May.

As of Monday (Nov 30), there were 48 dengue clusters. The largest, in the area from Tampines Street 81 to Tampines Street 91, had 38 dengue cases in the last two weeks.

There were 284 cases of dengue in the week ending Nov 28, a slight increase from the 254 cases the week before.

A 79-year-old man died of dengue fever on Saturday (Nov 28) after being taken to Tan Tock Seng Hospital days before. He is believed to be the third person to have died of the virus in Singapore this year.

Checks on drains and other common breeding areas in the Toa Payoh Lorong 8 estate he lived in have been stepped up. The area was a former dengue cluster that had seven reported cases before being closed on Nov 23.

The NEA said it will continue to closely monitor areas with active transmission of dengue and eradicate potential mosquito breeding habitats.

It urged the public to continue being vigilant and to prevent mosquito breeding by doing the 5-step Mozzie Wipeout. This refers to measures to prevent mosquito breeding, which include removing stagnant water, inverting pails and plant pot plates, and capping bamboo pole holders.

People infected with dengue are encouraged to protect themselves from further mosquito bites by applying repellent as regularly as possible.

Those showing dengue-like symptoms should see a doctor early to be diagnosed.

The latest updates on the situation can be found at the Stop Dengue Now Facebook page and www.dengue.gov.sg or through the myENV app.