Dengue cases spike, with a further rise likely: NEA

A total of 554 cases were reported during the week ending Jan 9 - 96 cases more than the previous week, according to the National Environment Agency, which added that a change in the main type of dengue virus circulating could be an early indicator of a future outbreak.
Channel NewsAsia 12 Jan 16;

SINGAPORE: There has been an “increasing trend” of dengue cases in Singapore, with the figures likely to rise as the weather heats up, the National Environment Agency (NEA) said on Tuesday (Jan 12).

A total of 554 cases were reported during the week ending Jan 9, 96 cases more than the previous week, latest figures on the NEA website showed. Between Jan 10 and 3.30pm on Jan 11, there were another 121 reported cases.

NEA warned that there has been an increase in the Aedes mosquito population, with the warmer-than-usual weather shortening the breeding and maturation cycles of the mosquitoes, as well as the incubation periods for the dengue virus.

It said source eradication of mosquito breeding habitats remains a key component in preventing the spread of the virus, which is why intensive source reduction exercises (ISREs) have been stepped up,

"Previously, it was actually done in mid-February to March itself, but within this year, because of the high number of dengue cases, as well as the temperature changes, NEA has urged all stakeholders to start the ISREs, some of them in December itself. But most of us started in January, at the start of the year," said Mr Albert Lee, a councillor for the Singapore Pest Management Association.

Additionally, the proportion of dengue cases due to the DENV-2 serotype has increased and now accounts for more than two-thirds of all dengue cases serotyped in Singapore, the agency said. Previously, the DENV-1 serotype accounted for most of the dengue cases in Singapore since March 2013.

“This change in the main circulating dengue virus may be an early indicator of a future dengue outbreak, unless measures are taken to suppress the Aedes mosquito population,” NEA said on its website.

Currently, Singapore's biggest dengue cluster is in the Tampines area, with a total of 206 reported cases. As of Jan 7, the area had 195 cases, 81 of which involved foreign workers at a construction site.

The Land Transport Authority said all the affected workers have since recovered and are back at work.

The chairman of the Government Parliamentary Committee for National Development and Environment Lee Bee Wah said more needs to be done to raise awareness of the dengue problem.

"From my experience of doing house visits - whenever there are dengue cases, I try to visit that block - when I talk to residents that there are dengue cases in this block, some residents ask me 'are there?'. So that means the awareness is still not there," said Ms Lee, who is also an MP for Nee Soon GRC.

To help stem the transmission of the virus, NEA reminded the public to check their premises daily for potential mosquito breeding habitats.

“Residents with plants in vases should change the water and scrub the inside of the vases every alternate day to prevent mosquito breeding. Those infected with dengue should also apply repellent as regularly as possible to prevent mosquitoes from biting and picking up the virus from them, and those showing symptoms suggestive of dengue should see their GPs early to be diagnosed,” it said.

- CNA/cy/ek


Dengue cases, already at record, likely to rise
LOUISA TANG Today Online 12 Jan 16;

SINGAPORE — It is barely halfway through January and Singapore is already seeing a record number of dengue cases, an unusual trend for this time of the year. Today (Jan 12), the National Environment Agency (NEA) warned that figures are likely to rise as the weather heats up.

The proportion of dengue cases due to the DENV-2 serotype, a common type of dengue virus here, has also risen sharply and now accounts for two-thirds of all dengue cases here, up from about half of all cases just a month ago, the agency said in an advisory. The DENV-1 serotype has accounted for most cases here since March 2013.

The NEA attributed the spike in cases to an increase in the Aedes mosquito population and a “slightly warmer-than-usual year-end weather due to the El Nino phenomenon”, which shortens the dengue virus’ incubation periods as well as the mosquitoes’ breeding and maturation cycles.

“This change in the main circulating dengue virus may be an early indicator of a future dengue outbreak, unless measures are taken to suppress the Aedes mosquito population,” the NEA said.

Between Jan 3 and 9, there were already 554 dengue cases — 96 more than the 458 cases seen the week before that, which was the highest recorded in 2015. Another 121 cases surfaced from Jan 10 to 3.30pm on Jan 11. The figures are higher than in past periods: In the first week of January 2013, there were about 125 cases, and in the same period in 2014, there were about 425.

Associate Professor Ooi Eng Eong, deputy director of the Duke-NUS Medical School’s Emerging Infectious Disease Programme, explained that to have DENV-2 resurfacing now — after it was the predominant dengue virus from 2007 to 2013 — may not be due to a lack of herd immunity, which is the threshold proportion of a population that has been infected before an epidemic dies out.

Herd immunity may drop with new birth cohorts and influx of people, but Assoc Prof Ooi believes there are other factors at play. “The replication of the dengue virus genome is error-prone, and occasionally gives rise to strains that spread more effectively in populations,” he said.

The good thing is that those who had been infected with the DENV-2 virus would not get it again, he added.

Infectious diseases professor Annelies Wilder-Smith from Nanyang Technological University’s Lee Kong Chian School of Medicine said this switch in serotype from DENV-1 to DENV-2 “is not unusual”, and could be the reason behind the continued dengue outbreak. “For now, we see an outbreak that is unusual for this time of the year, and it could indeed herald a larger outbreak year for 2016,” she added.

Two dengue types most common here:

There are four different dengue serotypes, with DENV-1 and DENV-2 being the two most common ones here.

The DENV-2 virus is more complex than other serotypes, because it changes structure in the human body, preventing previous antibodies from binding to new structures. Various strains can emerge as the virus mutates, with some spreading more easily than others.

In 2013, Singapore faced its worst dengue epidemic: Over 22,000 people were infected and seven died when the dengue serotype being transmitted switched from DENV-2 to DENV-1. Clinical trials are expected to begin at the end of this year after a team of scientists and engineers in Singapore said they have engineered an antibody that can neutralise all four virus serotypes.

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