From: Meer Ahmad, via email

Surprisingly, the World Health Organisation in its fact sheet on dengue fever says that the only method available in the control and prevention of dengue fever is to reduce the Aedes aegypti population, and that of secondary Aedes vectors. The Ministry of Health in Malaysia, I believe, is forced to subscribe to that.

I believe a strategy adaptated from that which ended malaria would be effective: early detection of cases, prompt notification (through a Health Ministry phone hotline), prompt isolation of all dengue cases in special dengue wards (for the period of communicability, which is mostly five days), and prompt insecticide-fogging of homes and work places where cases arise.

Vaccination, the use of mosquito-repellent patches (which only need to be stuck to one’s clothes for whole-day protection), and efforts at reducing the Aedes population would be additionally advantageous. The aim is to reduce the dengue reservoir.

It is a public health principle that all cases of an infectious disease with high morbidity, high mortality, and high transmissibility be isolated. SARS, H1N1 and Ebola were mostly controlled by isolation (including barrier nursing). Isolation is mandatory in cases of yellow fever, which is also an Aedes-borne disease.

Such special dengue wards do not require more than screening of windows and doors, regular fogging of the surroundings, and regular spraying of the wards with commonly available aerosol insecticide. Barrier-nursing is not required.

The above strategy is particularly viable when used with detection as early as the first day, at clinics and hospitals. This is possible now with the recent widespread availability of the NS1 Rapid (instant) Antigen Test which requires only three drops of blood, reminiscent of the old malaria blood-film.

All patients with fever should have the NS1 Rapid Antigen Test done, subsidised by the ministry. If cost is a constraint, tests need be done only on those with fever associated with headache, joint pain, body ache, and rash, or those with diarrhea, vomiting or abdominal pain preceded by fever.

The full blood count, including the platelet count, would not reveal anything until the third day.

Granted that 50 per cent of dengue infections are asymptomatic (according to the US Centres for Disease Control and several other sources), we can a achieve 50 per cent reduction of dengue with the above strategy. Complete coverage of vaccinating the entire Malaysian population cannot be expected to be achieved in more than a decade, and can be expected to be costly.

The mainstay of prevention would be vaccination, use of mosquito repellents and efforts at reducing the Aedes population.

It is good to hear that vaccines other than Sanofi’s Dengvaxia are in the offing, as are anti dengue-virus drugs, and immuno-therapy, but my above strategy will certainly control or eradicate dengue fever.

Dengvaxia was found to be about 65 per cent effective in a trial done in Malaysia, and about 80-90 per cent effective in preventing severe dengue requiring hospitalisation. It was found ineffective in children below five years of age (but increased herd immunity in the nation would also protect them).

There is no necessity to wait for the ideal vaccine. The cholera vaccine had an overall effectiveness of only 30 per cent, and it was not differentiated in effectiveness between mild and severe cases, but was promptly approved in this country. The Ministry must quickly approve the Dengvaxia vaccine, and make it adequately available in the country.

Everyone must protect themselves against the Aedes mosquito, especially pregnant women. The best method at present is the citronella (natural) mosquito-repellent patch sold at RM15 for 10 at pharmacies. The Health Ministry should sell these repellent-patches, at a subsidised rate, at its clinics throughout the country and give enough publicity on the availability of these patches at its clinics.

The Ministry must also make the NS1 Rapid (instant) Dengue Antigen Test available at all clinics and hospitals throughout the country, subsidised in a manner that it costs no more than RM30-50 per test.

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Meer Ahmad is a retired public health consultant and an FMT reader.

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