Dengue morbidity and mortality have surged considerably in the last decade. We compared the dengue prevalence in two decades since dengue became endemic in most countries after 2000. Official data was unavailable before that. The number of dengue cases in the Philippines surged to nearly 2 million (a 5‐fold increase) between 2011 and 2021, from only 462,780 in the previous decade.

However, case fatality was lower in the recent decade. Vietnam also witnessed 10 million dengue cases during 2011–2021. India and Sri Lanka were the first and second most dengue‐affected countries during the last decade (2011 to 2021) in the South Asia region, while the case fatality rate was higher in Pakistan (0.49). 

Dengue has served a severe blow in Latin America too, particularly in Brazil and Mexico. In Brazil, dengue crossed 10 million from only 5 million between 2011 and 2021, while dengue cases increased about three‐fold in Mexico (from 436,961 to over 1.5 million).

Bangladesh has also been experiencing frequent dengue outbreaks in recent decades. The first officially recognized dengue epidemic was in 2000 when the virus infected 5,551 individuals and killed 93 patients. After a period of decline, dengue rose again in 2015 and crossed 5,000 cases four times in the last five years. The number of dengue incidences surged to 101,354 cases during the largest outbreak in 2019, a 10 fold increase in dengue cases from the year before. In 2022, a total of 62,382 individuals were infected by dengue. Moreover, 281 patients also died, the highest in any year.

But this year, the situation is the worst. Up to date, the total effected cases are 247,193 with deaths of 1206 which are four and more than four folded than the previous year respectively. 

The existing dengue control strategies, such as diminishing vector breeding sites, using insecticides, chemical spraying, and personal protective measures have been found less effective and do not confer long‐term protection against vector‐borne diseases. Besides, these methods are season‐dependent and effective in limited areas such as houses or neighbourhoods.

Recently, insecticide resistance has become a serious concern worldwide, particularly in developing countries. A meta‐analysis suggested that a large number of mosquito population in developing countries in Latin America and the Caribbean has become resistant against commonly used insecticides such as Dichlorodiphenyltrichloroethane (86.7% ± 0.1%), temephos (75.7% ± 0.1%) and deltamethrin (33.0% ± 0.1%). Another study found that Southeast Asian countries, including Myanmar, Malaysia, and Thailand have become resistant to several insecticides, predominantly Deltamethrin, Permethrin, DDT, and Temephos. A. aegypti in Bangladesh was also found resistant to insecticides predominantly to pyrethroid. Increased resistance of local mosquito populations against frequently used insecticides may considerably limit the success of vector control strategy.

The Wolbachia‐mediated intervention method is ecologically friendly and can act without adverse effects on humans, animals, and the environment. It is well established that Wolbachia is a naturally occurring obligate endosymbiont and cannot survive in the environment without the host Wolbachia are gram‐negative bacteria that live inside host cells and infect somatic and germline tissues. These bacteria grow naturally in 40%‐60% of all insect species, maintain a symbiotic relationship with hosts and effectively play a key role in host transmission to the population by altering reproductive mechanisms and favouring Wolbachia carrying female insects. Similarly, W. pipientis infects the mosquito host and interferes with its reproductive cycles via a series of reproductive abnormalities, including alterations of the male sperm, manipulation of the developmental process, and interruption of the nutritional uptake of the host. 

Wolbachiapipientis is an endosymbiont in arthropods and nematodes that can induce reproductive manipulations by genetic modifications and epigenetic effects. Due to the vertical transmission of the endosymbiont to the germline, the epigenetic effects are trans-generational. Wolbachia’s maternal effects include male‐killing, feminization, parthenogenesis, and, most remarkably, cytoplasmic incompatibility (CI). 

Several successful field trials have been conducted to evaluate the efficacy of Wolbachia‐infected A. aegypti in controlling mosquito‐borne diseases. Dengue control approaches have been initiated by implementing more extensive field trials in Australia, which was later adopted by more than ten countries worldwide through the World Mosquito Program (WMP). The randomized control trial in Indonesia demonstrated exemplary results in mitigating dengue incidence. A. aegypti significantly lost its transmission ability after being infected with the wMelstrain and showed a 77% reduction in dengue cases. Previous studies showed that Wolbachia populations could persist in host populations for several years after release. Results from ongoing trials depicted that Wolbachia infections in hosts in Australia remained at approximately 100% for over eight years and reduced 96% of dengue incidents, while the same infection rate persisted in Indonesia for over two years (77% reduced dengue incidents). Furthermore, a study in Malaysia found an infection rate of 80% over two years, albeit a fluctuation was observed. 

Costs associated with the diagnosis and treatment of dengue pose considerable economic burdens in developing and least‐developed countries. Shepard and colleagues estimated dengue’s average annual economic burden in 12 Southeast Asian countries was about 950 million USD ($610 m–$1,384 m). The situation is much worse in Latin America, where dengue cases are surging. A systematic review by Lasernaet al. found the average annual cost to be over 3 billion USD.

Therefore, implementing Wolbachia introgression could curtail insecticide use eventually replacing them. Moreover, Wolbachia does not adversely affect traditional insecticides, including pyrethroid and organophosphate insecticides used for Aedes mosquitoes control and therefore could be used along with insecticide.

The writer is the Head, Department of Entomology, NIPSOM, Dhaka