The number of people hospitalised with dengue during 2011 rose 25 per cent from the year before and the number of deaths almost doubled, health officials said yesterday.

Ngan Chantha, head of the National Dengue Control Programme, said 15,805 people were hospitalised with dengue between January and the middle of last month and 72 of those  died. In 2010, about 12,500 people had been hospitalised with dengue, 38 of whom died.

Nima Asgari, public health specialist for the World Health Organisation, said last year’s figures “were higher than average, but they weren’t high enough to classify it as an outbreak”.

“We were concerned about it . . . but it subsided,” he said, adding that numbers were not of the same magnitude as in 2007 when more than 40,000 Cambodians were hospitalised with dengue.

The increase in the number of deaths from dengue last year was caused by a variety of factors, Asgari said.

These included outbreaks in areas where dengue had not been prevalent in recent years, and delayed detection and treatment, he said.

Ngan Chantha said climate change was partly to blame because increased rainfall and flooding left more breeding spaces for mosquitoes that transmit the virus, and prolonged the dengue season.

Nima Asgari, however, said there was insufficient data to connect climate change with the rise in deaths from dengue.

Both agreed the cyclical nature of dengue outbreaks was a factor.

“Outbreaks depend on the amount of immunity that develops in a community,” Asgari said.

“As more people become exposed to it, they become immune to it, and then you see a change in serotype and that decreases immunity so you expect to see an increase in dengue cases every few years,” he said.

Dengue has hit the Asia-Pacific region the hardest and Cambodia is among the worst-affected countries in the region, the WHO says.