PETALING JAYA - The current surge of dengue cases is the result of a change in variation of the dengue virus, the Health Ministry in Malaysia said.
Deputy Health director-general Datuk S. Jeyaindran said there was usually an outbreak whenever there was a change in the dengue virus serotype as fewer people would be immune to the serotype after the change.
Moreover, the current serotype, DEN-2, was more virulent, he said, adding: "That is why we are seeing more deaths."
It was reported that 10,712 cases and 19 deaths were reported this year up to Feb 6 compared to 2,836 cases and eight deaths over the same period last year.
Based on previous reports, Malaysia experienced its worst dengue outbreak in 2008 with 49,335 cases, while the highest death toll was in 2010 with 134 fatalities from 45,901 reported dengue cases.
The numbers dropped the following year until last year when it began to increase again.
Dr Jeyaindran said that the DEN-2 serotype was discovered sometime mid-last year.
"Before that, it was the DEN-4 serotype," he said.
"The DEN-2 serotype cases appeared to have started in Singapore and then were found in Johor at the end of last year and subsequently reached Malacca, Negri Sembilan and Selangor," he said.
Dengue infections are caused by four closely related viruses, namely serotypes DEN-1, DEN-2, DEN-3 and DEN-4.
Each has different interactions with the antibodies in human blood serum.
The change in serotype is one reason a major dengue outbreak could occur as individuals are protected from infections with the remaining three serotypes for only two to three months after the first dengue infection.
When two or more dengue cases are detected in a village or a residential area, it is considered an outbreak.