UNDER THE MICROSCOPE

Last week, the Department of Health released a statement stating that dengue cases had dropped 24.4 percent in the first two weeks of 2024 (2,024 cases versus 7,274 cases from Dec. 17-31, 2023, and 8,629 from Dec. 3-16, 2023), At least two major newspapers picked up this statement.

That in itself seems to be good news. But in the grand scheme of things, this is but a blip on the radar, so to speak. The statement has to be taken in context, as in what are the prevailing climatic conditions that are prevailing, since it has a lot to do with the ups and downs of dengue infections. A study by A. Sumi et al in the Cambridge University Press (2016) has established that not only rainfall has an effect on increasing dengue cases but so do relative humidity and temperature.

Hence, as we continue to have no to low rainfall, low humidity and dropping temperatures, mosquito-breeding activity likewise drops, with less chances of being bitten by dengue virus-carrying Aedes mosquitoes.

Even more, we need to take into account the total number of dengue cases in a year vis-à-vis the previous years if we are to see a trend, not just a two-week period. Per Statista, the number of dengue cases progressively increased from 2013, which saw a peak of 2,775 deaths in 2019. The DOH recorded 220,705 dengue cases and 722 dengue deaths in 2022.
Assuming that 93 percent of all reported dengue cases are hospitalized, as stated by E. Undurraga et al in American Journal of Tropical Medicine and Hygiene (AJTMH) vol 96 issue 4, that is an enormous economic burden. Edillo et al (AJTMH Feb. 4, 2015) estimates that dengue medical costs amount to US$345 million annually, which could otherwise go to other health campaigns like rabies prevention. It is a shocking amount in any currency, which we have to spend every year for dengue treatment.

So, are we supposed to heave a sigh of relief because of that DOH statement? The answer is a flat no. Where have we failed in our dengue prevention campaign? The DOH 5S campaign (Search and destroy mosquito breeding sites, Self-protection with insect repellents, Seek early consultation, Support fogging and spraying and Sustain hydration) has not really made a dent in our dengue statistics. 

Research shows that the major reservoirs of mosquito breeding are in non-urban areas, which are not amenable to eradication. Insect repellents are costly and not likely to be used by a majority of the population struggling with the rising costs of living. Folks usually self-medicate before they seek medical care. Fogging and spraying are only temporary measures and are environmentally harmful. Hydration can only be resorted to when already infected by the dengue virus (not preventive).

Clearly, we need more than the 5S program to address dengue. The abrupt discontinuation of the Dengvaxia vaccination program prevented us from fully evaluating its public health effects. 

Now a second dengue vaccine, Qdenga, has been approved by the European Medicines Agency. Qdenga maker Takeda has applied for FDA approval in the Philippines. 
Another promising mosquito vector control method is the transfection of mosquitoes by Wolbachia pipientis, which effectively reduces replication of RNA viruses in insects, including dengue. This is still in the experimental stage, thus not available for public health use.

Our health authorities have the responsibility to explain what the DOH press release really means other than just stating the obvious. Is it due to climatic factors (which it most probably is), or interventions? If the latter, which worked, if ever? The figures have to be explained in the context of the cyclical nature of epidemics, if nothing else.
Reporting figures without context may simply be pandering to the public imagination that dengue is under control, which it isn’t. That smacks of misinformation.