Dengue infections this year surged past the 10,000 mark this week.
The National Environment Agency (NEA) said on its website: “This is the highest number of cases for the same period of the year since 2013, the largest outbreak year recorded in Singapore’s recent history.”
As we enter the traditional dengue peak season (typically from May to October), NEA warned that weekly dengue case numbers are likely to continue to rise, with the warmer weather facilitating growth of the Aedes mosquito population and transmission of the dengue virus.
A combination of factors could have contributed to the recent spike in cases. This includes a change in the dominant strains of the dengue virus, from serotypes DENV-1 and DENV-2, to DENV-2 and DENV-3.
DENV-3 has not been dominant in the past three decades, but it accounted for more than 40 per cent of infections in the first quarter of 2020.
Assistant Professor Vincent Pang, Director of the Centre for Infectious Disease Epidemiology and Research, said:
“Herd immunity usually occurs when a large number of individuals in the population develop immunity against a serotype of dengue after being infected by it.
It is likely that herd immunity against the serotypes DENV-1 and DENV-2 has been established here. However, the change in dominant strains means that fewer people would be immune to DENV-3 and there is a lack of herd immunity towards this serotype.”
In addition, with current COVID-19 measures in place, more people are staying and working at home during the day. This could put them at greater risk of transmission as the Aedes aegypti mosquito, which transmits dengue, dwells mainly in indoor spaces and primarily bites during the day.
“For those of us who are spending more time at home due to the ongoing restrictions, it would be wise to take extra precautions, especially removing stagnant water from around the household and common corridor,” said Vice Dean (Research), Associate Professor Alex Cook.
He added, “We really want to avoid having the hospitals stretched by two outbreaks at the same time.”
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