NEA and MOH urges all to stamp out the Aedes mosquito population to moderate increase in dengue cases

19 Jun 2007

Those living in dengue hotspots warned to take extra measures

Singapore is facing an increase in dengue cases. The weekly number of dengue cases reported last week was 401, a 37% increase from 293 cases reported in the preceding week. A total of 2868 cases were reported during the first 24 weeks of 2007 compared to 1392 cases for the same period in last year. Two local dengue deaths have been reported so far.

The recent spells of intermittent rain coupled with warm weather has provided the mosquito ample opportunities to breed in minute pools of stagnant water all over the island. A change in the predominant strain of virus from Den-1 to Den-2 has also contributed to the spike in cases of dengue. For the first time this year, the "epidemic threshold" of 378 cases was crossed. The "epidemic threshold" for dengue is an abitrary number reflecting the mean number of weekly dengue notifications in the past five years (2002 - 2006) plus two standard deviations. This marker monitors the time periods where the number of dengue cases is significantly higher than the average weekly number of cases reported in the past five years. To keep dengue cases in check, NEA and MOH urges all to continue to stay vigilant and stamp out the Aedes mosquito population. This will help to moderate any further increase in dengue cases.

The National Environment Agency (NEA) together with 25 members of the Inter-Agency Dengue Taskforce will continue with their stepped-up measures doing daily checks on the ground to search out and destroy breeding habitats. Other than homes, checks are being done in outdoor areas, drains, buildings, construction sites, parks, vacant land -- any infrastructure or facility that can breed mosquitoes.

Since the month of May, NEA has stepped up its checks especially in homes -- 171,022 inspections were conducted compared to 85,218 in April. The number of inspections in May are also more than three times that the number carried out in May 2005,  Other than NEA's 500 environmental health officers who are suppressing the mosquito population through 24,000 hours worth of search and destroy efforts on the ground, a further 300 officers from other departments have also been deployed since end May. In total, NEA is devoting 30,000 hours a week to ensure as many breeding habitats including potential ones are removed. By removing these breeding habitats, there will be fewer mosquitoes and thus a reduction in the risk of more people being infected with dengue.

To tackle dengue fever, NEA will continue with its current operational efforts concentrating on:-

a) Breaking the transmission cycle in clusters through intensive source reduction efforts

b) Taking preventive action in priority areas particularly susceptible to dengue fever because the areas have not seen a predominant number of Den-2 cases in the last five years. Officers have also been assigned to comb for breeding spots on a daily basis in other areas that show signs of possible  clusters. These are Yishun, Marsiling, Woodlands, Bedok North, Ang Mo Kio and Taman Jurong.

Breaking dengue transmission in clusters

More than half of the 500 strong Environmental Health Officers contingent have been assigned to fight ongoing dengue transmission in the current 77 clusters. It is crucial that the transmission cycle be broken in these areas as soon as possible, so that people living in the area would not be at risk from coming down with dengue.

To help residents in clusters protect themselves, details of clusters with 10 or more cases are provided on NEA's website from today. The public is advised to check out the list and to take extra precautions like spraying aerosol in dark corners of homes, e.g behind curtains, sofa, cupboards and under the bed in early morning if they are living in the areas.

This year so far, we have had 296 clusters (more than the 77 clusters in 2006). NEA managed to close the majority of them (71.9%) under 10 days keeping average cases per cluster to 2.4.

There are currently 10 clusters with 10 or more cases. The largest are at Kim Keat Road/Kim Keat Close and West Coast Drive/West Coast Walk with 23 cases each. Breeding inside homes remains a challenge in these areas.

NEA is also concerned with clusters at West Coast Road  (15 cases) and Ho Ching Road/Tao Ching Road/Yung Sheng Road (13 cases). These two clusters have had a duration of one month and though officers have combed all the homes and outdoor areas, breeding is still found in homes.

Indeed, like the Jln Songket / Hougang St 21 (Blk 220, 221, 222) / Aroozoo Ave / Surin Ave / Jln Samarinda / Jln Mastuli / Jln Pelikat cluster which recorded 32 cases, breedings found in homes was the predominant cause for these three clusters' continued persistence. Homes breeding accounted for 86.8% of breedings found in the Jln Songket / Hougang St 21 (Blk 220, 221, 222 ) / Aroozoo Ave / Surin Ave / Jln Samarinda / Jln Mastuli / Jln Pelikat cluster, 76% in the West Coast Drive/West Coast Walk cluster, 100% in the West Coast Road cluster and 70% in the Ho Ching Road/Tao Ching Road/Yung Sheng Road cluster.

Pre-emptive efforts

Other than fighting clusters,  the 300 non-Environmental Health NEA officers are deployed to minimize the chances of  dengue transmission and prevent clusters from occurring in 50 priority areas. Based on NEA's records for the past 6 years, 44 of the 50 areas (please see list attached) are vulnerable to the disease because many living in the areas have little or no exposure to the Den-2 virus. As for the remaining areas (listed above), NEA’s analysis show these areas to have a higher chance of cluster formation hence stepped up efforts.

The Government's efforts to prevent more people from coming down with dengue will need the collective efforts of all to prevent mosquito breeding. While government agencies continue to keep public areas in check, homeowners are also urged to rid their homes of stagnant water on a daily basis by doing the 10-minute Mozzie Wipe-out. Mr Khoo Seow Poh, NEA’s Director-General of Public Health said: “To suppress the mosquito population, every effort in removing stagnant water counts. This include efforts in homes and outside homes. NEA, Town Councils, land agencies and homeowners must continue to be vigilant as one community in this fight against dengue."

For the first 23 weeks of the year, NEA has uncovered 2,354 breeding habitats in homes, 86.7% more than the same period in 2006 and 5.4% more than the same period in 2005.

While we sustain our efforts in preventing mosquito breeding, MOH also advises the public to seek medical attention immediately if they feel unwell and have a fever during this period. If they are diagnosed by the doctor to have dengue, they should follow the doctor's advice and:

Ensure that they have adequate rest and drink enough water to prevent dehydration

Protect themselves and their household members from mosquito bites, eg, by using mosquito repellent or mosquito coils. This will help protect their families from contracting the disease.