Continued vigilance needed to prevent year-end rise in dengue cases amid higher circulation of less common Dengue virus serotype 3 (DENV-3) in large dengue cluster areas

Singapore, 26 October 2021 – Over 4,500 dengue cases have been reported in Singapore since the beginning of this year, and there are currently 12 active dengue clusters. Recent weekly dengue cases have been lower than during the same period in 2020, following the two-year dengue outbreak that spanned 2019 and 2020. However, NEA urges members of the public and other stakeholders to stay vigilant and not to let our guard down, as dengue remains a serious public health threat.

2          Of significance is the increasing Aedes aegypti mosquito (the primary dengue vector) population across the island. The population increased by about 22 per cent in the month of September 2021 compared to in August 2021, and is high in some areas of Singapore, including Geylang Bahru, Jalan Berseh / Kelantan Lane / Kelantan Road, Jelapang Road, and Woodlands Street 81.

3          The proportion of dengue cases due to the less common Dengue virus serotype 3 (DENV-3) has increased. DENV-3 has replaced DENV-2 as the dominant serotype, and has accounted for more than 50 per cent of the serotypes sampled since May 2021. DENV-3 has been detected in 121 (of 254) dengue clusters where serotypes were identified this year, including the ongoing 195-case cluster at Florence Road / Hougang Avenue 2.

4          Prior to 2020, DENV-3 had not been the dominant serotype during any major dengue outbreaks in Singapore over the past three decades. Thus population immunity against DENV-3 is low, and more people are susceptible to infection with this serotype.

5          Many people are currently staying in and working from home, which could translate to more biting opportunities for the day-biting Aedes aegypti mosquito, and thus potentially higher risk of dengue transmission. The incidence of Aedes mosquito breeding detected in homes remains high.

6          If left unchecked, the current high Aedes aegypti mosquito population, coupled with circulation of the previously uncommon DENV-3 and a sizeable proportion of people staying in and working from home, would add to the dengue risk this year-end. NEA therefore urges all members of the public to prevent mosquito breeding, by immediately practising the following Mozzie Wipeout steps at least once a week, to remove stagnant water:

Mozzie Wipeout ‘B-L-O-C-K’

Break up hardened soil
Lift and empty flowerpot plates
Overturn pails and wipe their rims
Change water in vases

Keep roof gutters clear and place BTI insecticide inside

7          From January to September 2021, NEA conducted about 523,000 inspections for mosquito breeding islandwide, and uncovered about 14,300 mosquito breeding habitats. During the same period, more than 5,500 enforcement actions were taken against premises owners for mosquito breeding [1]. 

8          All premises owners and operators should ensure that comprehensive vector control measures and good housekeeping are in place. NEA continues to conduct targeted inspections at areas with higher mosquito population, and has stepped-up operations at dengue cluster areas. All residents, especially those living in dengue cluster areas, are encouraged to carry out the three protective actions against dengue:

Protective actions against dengue: ‘S-A-W’

Spray insecticide in dark corners around the house
Apply insect repellent regularly
Wear long-sleeve tops and long pants