Dengue fever cases are creeping up again as Singapore enters the traditional peak dengue season, with the number of cases exceeding 200 a week for the fourth week in a row.

There were 223 reported cases of dengue last week, slightly down from 246 the week before.

On June 25, a 72-year-old woman in Simei became the sixth victim here to succumb to dengue this year. In the whole of last year, four people died from the virus.

The National Environment Agency (NEA) and Ministry of Health (MOH) are "anticipating an upward trend in the number of dengue cases in the coming months".

Since April, the NEA has found 50 per cent more Aedes mosquitoes, which spread the virus, caught in its Gravitraps islandwide.

A total of 9,641 cases have already been reported this year. Over all of last year, just over 11,200 people were diagnosed with dengue.

The NEA said in February that there could be more than 30,000 cases this year - higher than the historic 22,170 cases reported in 2013.

The year started with cases at an unusual high, at one point surpassing 600 a week in January despite it being the traditional low season.

The cases fell to a low of 158 in the second week of June but have now started to rise again.

The Asian Dengue Vaccination Advocacy, a scientific group of dengue experts across the region, said it expects the recent "alarming rise" in cases to continue, partly due to climate change. It added: "The spike in cases cannot be seen in isolation as factors such as large-scale urbanisation make it easy for the Aedes mosquito to breed."

There are now 44 active dengue clusters in Singapore, down from 49 last week. Of these, eight are classified as high-risk.

The biggest is the Dunbar Walk-Telok Kurau cluster, where 70 cases have been reported since the cluster started, 12 of these in the past two weeks.

The Jalan Ismail-Lorong Marican cluster in Eunos has had 49 cases, and the Admiralty Drive-Sembawang Drive one has had 48.

Of the six people who died from dengue this year, three were in their 70s and two in their 60s. The youngest was a 47-year-old man.

Infectious diseases expert Leong Hoe Nam from Mount Elizabeth Novena Hospital said that the elderly, especially if they have conditions such as lung or heart problems, tend to be more susceptible to the virus. "Dengue can be the final straw that pushes them over," he said.

Domestic containers remain the most common breeding ground for the Aedes mosquito at home, followed by flower-pot plates or trays and ornamental containers.

Following the latest death on June 25, the NEA found and destroyed a mosquito-breeding site in a bamboo pole holder at Block 135, Simei Street 1.

The NEA and MOH reminded residents to cap bamboo pole holders when they are not in use.