Desk Report
Publish: 29 Aug 2021, 10:06 pm
Representational Image || Photo: Collected
New strains of less common dengue
serotypes, which are usually imported, could raise the risk of a larger
outbreak, say experts.
Of the four distinct dengue virus variations,
the DenV-1 and DenV-2 serotypes are most commonly seen here. The majority of
infections since 2016 have been caused by DenV-2 - meaning that most recovered
dengue patients would have immunity against this serotype.
A virus serotype also has distinct strains, which are genetically different but create the same immune response to different degrees, depending on the strain, in the body.
new strains are usually introduced through imported cases. Such viral strains can subsequently circulate more widely due to factors such as lower population immunity to the less common serotypes and better virus replication in the mosquito and human.
Warmer and rainier weather can also lead to rising mosquito
populations and increased feeding.
Professor Paul Tambyah, president of the Asia-Pacific Society of
Clinical Microbiology and Infection, said it is possible for one strain to
become more dominant if immunity to the other strains have developed.
He noted that past studies by the NEA found that several DenV-3
strains had been behind infections in different areas in Singapore.
Analysis of those DenV-3 samples had identified three genotypes
closely related to those found in Indonesia, Malaysia, the Philippines,
Thailand, Saudi Arabia and Cote d'Ivoire.
With the drastic reduction in international travel this year,
however, it is less likely that a new "variant" of DenV-3 would have
been introduced, Prof Tambyah said.
Nonetheless, noting that the Delta variant of the Sars-CoV-2 virus has managed to seep in despite the curbs in international travel, it is still possible for DenV-3 strains to be brought in by travellers, he added.
The recent rise in dengue cases could be due to more people
working from home during the period of heightened alert. This gives the Aedes
aegypti mosquitoes, which are day biters, more opportunities and some of them
may carry the DenV-3 serotype.
This was also the postulation for the 50 per cent spike in dengue
infections during the circuit breaker period last year.
Assistant Professor Vincent Pang, director of the Centre for
Infectious Disease Epidemiology and Research at the National University of
Singapore's Saw Swee Hock School of Public Health, said the risk of getting
bitten by DenV-3-infected mosquitoes depends on several factors. These include
whether there is mosquito breeding in the area.
DenV-3 infections would also likely be higher in areas where
people have low immunity against the serotype, such as when there is herd
immunity against both the DenV-1 and DenV-2 serotypes.
"However, if there is sustained compliance to dengue
preventative measures, such as removing stagnant water to prevent mosquito
breeding and using insect repellent, then the risk of getting bitten would be
much lower," he said.
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Topic : Dengue DenV-3 strains
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