PETALING JAYA: It’s been raining in the Klang Valley, and there have been hot spells in between – and that’s the perfect climate for the hatching of Aedes mosquito larvae, say experts.

       Former deputy health minister Dr Lee Boon Chye said the intermittent rain and dry period helps Aedes mosquitoes breed and can cause an upsurge in dengue cases.

       “A prolonged drought or prolonged rainy season will have the opposite effect,” he added.

       Climate expert Prof Datuk Dr Azizan Abu Samah said the major peak for dengue cases in the Klang Valley in terms of climate is around June.

       However, the peak season may differ in other parts of the country depending on the weather.

       “Dengue breeding is sensitive to temperature and rainfall. However the correlation between rainfall and dengue larva is higher in comparison to temperature,” he said.

       The Aedes larva typically lives in water.

       A banner about dengue is displayed in Petaling Jaya.

       “The egg of an Aedes mosquito can hatch into a larva in less than a day, if the conditions are conducive.

       It then takes about six days before it becomes an adult mosquito.

       Public health expert Datuk Dr Zainal Ariffin Omar said there are two possible reasons behind an upsurge in cases.

       “The dengue virus grows and spreads in mosquitoes faster at higher temperatures, but slows when temperatures are below 30°C,” he said.

       He added that mosquitoes tend to breed in places where there was clean and stagnant water.

       Health director-general Tan Sri Dr Noor Hisham Abdullah has said that 16,145 dengue cases were reported between Jan 1 and May 21 this year.

       This represents a 52.4% increase from the 10,597 cases reported in the same period last year.

       “Nine deaths from dengue complications were also reported this year compared with five deaths in the same period last year,” he said in a statement last week.