Dengue cases up 53 per cent between July and September, one death reported

SINGAPORE – There were 3,055 reported dengue cases for the July to September period, a 53 per cent increase from the previous quarter, which saw 1,989 cases.

There was one death due to infection during that period, bringing the number of dengue-related deaths to three in 2023, according to data from the National Environment Agency (NEA).

As at last Saturday, there were 8,437 cases reported so far in 2023 – about a quarter of the 32,325 cases recorded in 2022.

NEA figures released on Oct 31 showed that the DenV-2 serotype accounted for 67.9 per cent of the infections in September.

This is in contrast to June and August, when the DenV-1 strain was dominant.

DenV-1 caused a major outbreak 10 years ago, with 22,170 dengue cases reported in 2013.

It replaced the DenV-3 strain that drove the dengue outbreak in 2022 and was the main cause of infections in the first half of 2023.

Of the four distinct dengue virus variations, the DenV-1 and DenV-2 serotypes are most commonly seen here.

Most infections since 2016 have been caused by DenV-2.

Dengue expert Tikki Pang told The Straits Times the increase in cases could be due to a number of factors. These include a rise in mosquito numbers, as increased rainfall together with higher temperatures from the El Nino phenomenon result in favourable breeding conditions.

In October, the NEA warned that warmer weather in the coming months due to El Nino – a climate pattern associated with the unusual warming of surface waters in the eastern tropical Pacific Ocean – could see the dengue situation becoming worse.

However, there is “no real cause for concern” with the re-emergence of the DenV-2 serotype, said Professor Pang, a visiting professor at the National University of Singapore’s Yong Loo Lin School of Medicine. He said that from time to time, different strains will become dominant.

The resurgence of DenV-2 cases may be due to people having waning immunity against the strain, as DenV-3 was the predominant serotype in the first half of the year, he said.

It is “definitely possible” that there could be a surge in dengue cases at the end of 2023 or the beginning of 2024 due to the different factors at play, he added.