The number of new dengue fever cases has begun to rise again after a downturn last month.
There were 378 recorded last week, 72 more than in the previous seven days, according to figures from the National Environment Agency (NEA).
Experts have already warned that there could be a major epidemic this year due to the unusually large number of infections at the start of the year - traditionally a low period for such mosquito-borne infections.
The Ministry of Health (MOH) and NEA have said that they expect to see more than 30,000 infections this year - far higher than the record 22,170 cases in 2013.
So far, more than 6,400 people have been diagnosed with the viral infection - three times the number seen at this time last year.
Four people have died this year, as many as the number who died of dengue in the whole of last year.
The NEA said most mosquito breeding sites found by its inspectors were in homes, in pails, flower pot plates and trays.
"Source eradication of mosquito breeding habitats and spraying of insecticides to control the adult mosquito population remain key to dengue prevention," it said on its website. Such efforts need to be kept up, it said, in order to mitigate "the forecast surge in cases".
A $200 fine was introduced on March 14 for anyone found to have mosquitoes breeding in their homes.
Previously, the penalty was imposed only on homes in active dengue clusters.
Mosquitoes mature faster in hot weather, and the current unseasonably hot spell is likely to see an increase in the population of the Aedes mosquito, which spreads dengue.
Another worry this year is the change in viral strain towards the end of last year. Historically, a change in strain always results in a surge in dengue cases. This is because of lower immunity in people against the new dominant strain.
There are four strains of dengue virus. Someone who has been infected is generally immune against a second infection of the same strain but is not protected against the other three.
A study here two years ago found that less than 15 per cent of people aged 16 to 25 were immune to Den-2, the current dominant strain.
A surge in dengue cases will also put a strain on public hospitals. The MOH said that generally, one in five people diagnosed with dengue requires hospital care.
If the infection rate hits 30,000 this year, it would mean 6,000 people requiring hospital treatment.