PETALING JAYA: Based on national data, the dengue trend follows a cyclical pattern with a dengue epidemic being reported every four to five years, says Tan Sri Dr Noor Hisham Abdullah.
The Health director-general said the recent dengue epidemic was also observed in 2014 and 2019 with an average of 2,300 cases per week and 2,500 cases per week reported respectively.
"Dengue is on the rise this year as part of its cyclical trend and it is anticipated to peak in 2023.
"The rising number of dengue cases are partly contributed by the change in dominant circulating dengue serotype or the 'serotype shift' which is a well-known reason for the occurrence of the dengue surge.
"It has been observed that dengue cases will increase usually four to six months after a serotype shift due to the lack of immunity in the community towards the new dominant circulating serotype," he said in a statement on Thursday (March 30).
From the Health Ministry’s surveillance monitoring, there was a shift of circulating dengue virus serotype from DEN 3 to DEN 4 since June 2021, Dr Noor Hisham added.
He said since then, DEN4 serotype was the dominant circulating virus serotype in the environment.
In terms of other contributing factors, Dr Noor Hisham said climatic change was an important factor especially with alternating rain and hot seasons.
"During the rainy season, man-made containers, or natural places, for example leaves of plants that retain water create potential places for the Aedes mosquitoes to breed.
"On the other hand, during the hot season, Aedes mosquitoes become more active in their biting behaviour and bite more humans, thus increasing the spread of the dengue virus.
"Poor environmental cleanliness with abundance of man-made containers has provided suitable breeding places for Aedes mosquitoes.
"Human behaviour of littering is among the main reasons for the poor environmental cleanliness," he said.
In 2022, Malaysia reported 66,102 dengue cases with 56 deaths compared to 26,365 cases with 20 deaths in 2021.
This was an increase of 150.7% of dengue cases and an increase of 180% of deaths in 2022.
Similarly, the rising dengue trend this year was also observed in other countries in the region, Dr Noor Hisham said.
On Tuesday (March 28), Deputy Prime Minister Datuk Seri Dr Ahmad Zahid Hamidi announced there was a massive 223% spike in dengue cases this year up to March compared to the same period last year in the country.