SINGAPORE - Close to 380 cases of dengue were reported last week, the highest weekly number reported in 2015 so far.

Senior Minister of State for Health Amy Khor, in a Facebook post on Tuesday (Dec 29), wrote that 377 dengue cases were reported in the week ending Dec 26.

"It is the highest weekly number reported in 2015 so far. The number is unusually high for this time of the year," she said.

Dr Khor, who is also Senior Minister of State for the Environment and Water Resources, said that due to the El Niño phenomenon, the weather is slightly warmer.

The warmer conditions support faster breeding and maturation cycles of the Aedes mosquitoes, and shorten incubation periods for the dengue virus, she said in the Facebook note.

In addition, the proportion of dengue cases due to the DENV-2 serotype has increased and now accounts for more than half of all dengue cases in Singapore.

Before, the more common serotype was the DENV-1. It accounted for most of the dengue cases since March 2013.

"This change in the main circulating dengue virus may be an early indicator of a future dengue outbreak," she wrote.

Four people have died of dengue fever this year, three in recent months.

Dr Khor urged members of the public to remain vigilant.

As of Nov 30, the National Environment Agency has conducted more than 1.3 million inspections islandwide.

It has also been raising awareness and alerting the public on dengue prevention through outreach efforts.