EXPERTS have raised the alarm that a dengue fever epidemic is set to hit Malaysia starting this year — with cases expected to peak in 2024 and 2025 — and are urging authorities to strengthen interventions and the public to take preventative steps.
The Health Ministry reported that dengue fever cases up to epidemiological week 51 (up to Dec 24) were three times higher than figures seen during the same period in 2021.
Up to Dec 24, Malaysia recorded a cumulative 64,078 dengue cases compared with 25,794 for the same period in 2021 — an increase of 148.4 per cent — while 50 deaths were caused by dengue complications compared with 19 during the same period in 2021.
This uptrend, however, came as no shock to experts, who described the phenomenon as a "cyclical transmission of dengue fever" that surges every three to five years.
The recent increase in dengue cases is expected, said public health expert and epidemiologist Professor Datuk Dr Lokman Hakim Sulaiman.
"Based on observations over the past three decades (in Malaysia), severe dengue outbreaks occur every four to five years.
"Last year was the beginning of the next major outbreak, which I predict will peak between this year and 2025."
Dr Lokman is the Pro-Vice Chancellor of Research and director of International Medical University's Institute for Research, Development and Innovation. He also served as director of the Infectious Disease Research Centre under the Institute for Medical Research.
Dengue was first documented in Malaysia in 1902 and became a public health risk in the 1970s.
Its first major outbreak occurred in 1973 (969 cases and 54 deaths).
Other major outbreaks were reported in 1998 (27,381 cases and 82 deaths), 2008 (49,335 cases and 112 deaths), 2015 (120,836 cases and 336 deaths) and 2019 (130,101 cases and 182 deaths).
Most dengue victims in Malaysia are between the ages of 15 and 49, and 80 per cent live in urban areas.
Epidemiologist and health informatician Professor Datuk Dr Awang Bulgiba Awang Mahmud of Universiti Malaya agreed, adding that the surge in cases was "hardly surprising" as dengue numbers normally went through an uptrend followed by a downtrend which is repeated over time.
He said this was due to the prevalent dengue virus serotype.
Dengue is caused by a virus of the Flaviviridae family.
There are four distinct, but closely related, serotypes of the virus that cause dengue (DENV-1, DENV-2, DENV-3 and DENV-4), all of which can be found in Malaysia.
Infection with one DENV serotype provides immunity to that serotype for life, but not to other serotypes.
Thus, a person can be infected four times, once with each serotype. Later exposure to the remaining serotypes is associated with an increased risk of severe disease.
"Cases will decrease as immunity builds up to one serotype.
"However, this downtrend is not permanent, and an uptrend is likely with a new serotype," Dr Awang Bulgiba said.
Over the past five decades, dengue cases have increased by 30-fold globally, with half of
the world's population now at risk.
According to the World Health Organisation, only nine countries had experienced severe dengue epidemics before 1970.
The disease is currently endemic in 129 countries, with 70 per cent of cases in Asia.
About 390 million people are infected each year, with 96 million cases showing clinical symptoms.
A 2019 study published in Nature Microbiology predicted that the geographical range of dengue will expand to put more than six billion people — or 60 per cent of the world's population — at risk of infection by 2080.
Climate change, population growth, unplanned or rapid urbanisation, ecological disruption, inadequate sanitisation and increasing international trade and travel have been cited as contributory factors to the increase in dengue cases.