Three people died from dengue in the last quarter of 2020, bringing the total fatalities for the year to 32.

This is the highest number seen here in a year, surpassing the 25 in 2005. In most years, fewer than 10 people here die of dengue.

With 32 deaths, dengue killed more people last year than Covid-19, which has claimed 29 lives.

Those who died were aged between 25 and 92.

Almost half, or 13 dengue deaths, occurred between July and September, according to the just released National Environment Agency's (NEA) quarterly dengue surveillance data for October to last month.

Last year, 35,315 people were diagnosed with dengue - more than double the infections in 2019, and 60 per cent above the previous high of 22,170 in 2013.

Generally, one in five people diagnosed was so sick that the person ended up in hospital.

Dengue causes nausea, vomiting, fatigue, aches and pain behind the eyes or in the muscles and joints, and, in the more serious cases, bleeding in the gums, nose or internally.

Although infections have fallen this month, typically the low season for the mosquito-borne disease, they are still higher than the numbers in 2017 and 2018.

NEA had flagged that the mosquito population rose by 8 per cent last month.

The latest data showed that while the majority of infections were caused by DenV-2 - which has been dominant here since 2016 - there has been a rise in the less common dengue serotypes.

There are four dengue serotypes, with DenV-1 and DenV-2 most commonly seen here.

However, infections by DenV-3 and DenV-4 climbed last year and accounted for 57.4 per cent of infections last month.

DenV-4, in particular, increased more than fourfold last year - from 4.8 per cent of infections in January to 23.1 per cent by last month.

The danger of a higher number of infections from lesser seen serotypes is the lower level of immunity in the population.

People infected by dengue are protected only against that particular serotype.

Since fewer people here have been struck by DenV-3 and DenV-4 in the past, the majority would be susceptible to them.

Earlier this week, NEA warned: "Risk drivers for dengue cases in 2021 include the continued high Aedes aegypti mosquito population and the current moderate number of dengue cases, amid higher circulation of the less common dengue virus serotypes 3 and 4 across the island."