A 79-year-old man has become the fifth person to die of the dengue virus this year, as fatalities surpass the four dengue deaths last year.

The Chinese Singaporean, who was not named, died at Tan Tock Seng Hospital yesterday, two days after he was admitted. He lived near the Eunos area, in Jalan Tenaga, which is in an active six-case dengue cluster, the Ministry of Health and the National Environment Agency (NEA) said in a statement yesterday.

The news comes despite a dip in dengue cases - 212 cases were reported from May 15 to 21, down from 216 from May 8 to 14, according to the NEA website.

Professor Tikki Pang, a visiting don at the Lee Kuan Yew School of Public Policy at the National University of Singapore who researches global health matters, said there may not be a link between the number of dengue deaths and dengue cases. Deaths tend to be related to patient-specific factors, he said.

He said one possibility was that the victims' immune systems could not cope with the dengue virus infection due to their age. "But other factors could be at play too - for example, late admission to hospital or other underlying risk factors."

Four of the five dengue fatalities this year involved patients aged above 60. A 47-year-old Singaporean man was the first to succumb to the dengue virus this year.

The elderly have weakened immunity so they and their caregivers should consult a doctor if there is any sign of a dengue infection, such as fever, said Mr Satyaprakash Tiwari, managing director of Care, a recruitment agency specialising in training caregivers for the elderly.

Yesterday, the authorities said operations to kill adult mosquitoes and destroy potential breeding habitats have been ongoing since May 12. They urged residents to stay vigilant as Singapore enters the traditional dengue season.

They added that, as most breeding spots are found in homes, the public should do the five-step Mozzie Wipeout, including inverting water storage containers and changing the water in vases regularly.