Letters
View(s):Preventive methods our only hope of beating dengue
Dengue prevention: PHI officers check boats in Beruwala
Sri Lanka has been fighting dengue with ad hoc measures now for more than 50 years. Enough is enough. We need a structural approach like what we had with the Malaria Control Programme which in the end eradicated Malaria from Sri Lanka.
We have failed in our strategy to control dengue because we concentrate on Mosquito Weeks and get the people to wake up from their slumber and do clean-up programmes. Secondly, we go after the mosquito but do not have a proper structure to sustain that effort and staff to man such a programme as the Malaria Control Programme had.
Globally estimates show that approximately 390 million people are infected each year and 96 million come up with clinically apparent disease. Dengue has an explosive epidemic potential and there is a worldwide increase in dengue cases. Compared with some countries we have not done badly especially as dengue has experienced a 30-fold increase in incidence over the past 50 years and shows no sign of slowing down. We have a 10-fold increase in Colombo after 20 years and one can see that it is not that high comparatively. The Global Strategy now is based on evaluation and integration of current intervention strategies to achieve a 50% reduction in dengue mortality and 25% reduction in dengue morbidity by 2020.
So our strategies should be based on 1) prevention of Aedes (dengue) mosquito breeding 2) prevention of transmission of dengue fever by infected dengue mosquitoes 3) getting rid of the virus.
Let’s look at going after the virus as the best option: either blocking the transmission of the virus from one patient to a healthy individual or vaccination. Theoretically this sounds fine. But to do that we must have a behavioural change at every level: In households, in hospitals, clinics, transport services, public gatherings, public and private institutions!
It would be better if we can have a vaccine to get rid of the dengue virus as we have done with other infectious diseases. But so far only one vaccine made in France has been approved by the WHO, that too for those between the ages of 12 and 45. It is said it doesn’t work in areas which have a predominant dengue virus 1 and 2 infections. The cost of the three doses for a four-year immunity period would be around Rs 10,000 per person over here. Can our Govt. cover the cost?
From 2002-2004, the newly introduced DEN-3 created epidemics in Sri Lanka and then 2009 it was DEN-1. What is the virus type circulating now? Is there a change in the virus which is causing the present epidemic? The Epidemiology Unit now says it is Den-2! So the vaccine seems out.
Even with the reduction of premises Index down from 50 to 2 there was a six-fold increase of the number of patients in Singapore after 50 years. If globally there was a 30-fold increase in 50 years and only a six- fold increase in that country it shows that Singapore has done truly well in their campaigns which I had the chance to personally observe. But the mosquitoes and viruses are clever. The mosquito finds new breeding sites while the virus changes its structure creating new clades against which we don’t have immunity to ward off the disease.
What we must understand is that one dengue mosquito cannot transmit the disease to another person which is not the real situation. Whether one gets the disease or not depends on whether that person has immunity against that particular dengue virus which circulates in the area, the number of mosquitoes involved in biting the person, the number of bites and the time period within which the person got bitten. In short on the dose of the virus that the person gets through mosquito bites and when the body’s immune system cannot cope up with it. By reducing the number of dengue mosquitoes in an area we can reduce the number of patients in that locality. However, with time when such areas reduce the number of mosquitoes to very low levels,the herd immunity gets lower and there is a good chance of a sudden eruption of an outbreak of dengue. The decrease in Aedes mosquitoes in Singapore caused a reduction in herd immunity and this process, coupled with the increased importation of dengue viruses into Singapore, led to an increase in transmission and a subsequent increase in disease incidence.
This is true for Sri Lanka too. All these facts show that controlling dengue is not easy but very complicated and the only thing we can do is to reduce the infection rate to a minimum by preventing the breeding of mosquitoes, look out for virus changes, and prevent dengue-stricken patients from being bitten and the transmission of the virus from those infected mosquitoes to healthy individuals.
At present Sri Lanka can afford only vector control to prevent an epidemic. Efforts have to be directed at the development and implementation of entomological research, such as the study of insecticide-resistance mechanisms, the monitoring of the efficacy of chemical and biological vector-control methods, and to identify the local environmental situations that help Aedes breeding. Efforts should be made to improve community involvement in dengue vector-control, in view of the fact that the presence of dengue mosquitoes depends on human behaviour. Even when an effective dengue virus (DENV) vaccine is available, the country should continue to rely on mosquito control because the two strategies complement and enhance one another. Source reduction, container removal, spraying around an identified dengue foci and larviciding also play a major role until then. For that we need human resources. All vacancies for public health staff should be filled.
A partnership by public health officials with the community to reduce the numbers of mosquitoes is a must. Repellents such as DEET and insecticide treated bed nets and or strips hanging in homes, hostels and hospitals where the mosquitoes rest and bite humans are potential components of prevention epidemics. In Australia Metofluthrin has been successful inside homes for such kind of prevention.
We must not forget that the same mosquito spreads Chikungunya, Zika and Yellow Virus too. Therefore, it is dangerous even to suggest that we move away from the strategy of preventing the breeding of Aedes mosquitoes.
Dr. Pradeep Kariyawasam
(Former Chief Medical Officer CMC)
Why not do away with sentries?
Day in and day out when I go past the Prime Minister’s official residence, Temple Trees, on my way to office, I feel sorry for the sentries stationed inside makeshift, mini- guard rooms, hoisted on L-iron (or is it H-iron?). Moreover, these enclosures have aluminum corrugated roofing sheets and the rest of the structure is also fabricated out of aluminum making it like an “oven to bake humans!” The security room for the solitary sentry at the Presidential Secretariat is also atop a similar metal structure.
With the hot weather nowadays, I think this is not how members of the security force should be treated.
Why don’t we completely do away with this existing outdated security system, when we have at our disposal more advanced modern technology like the CCTV security cameras which can be monitored by security personnel located in more conducive, convenient and spacious surroundings?
I am sure that both the President and the Prime Minister who are practical and down to earth will do away with the above system of providing security and implement a better alternative without compromising the much needed security for them.
Mohamed Zahran
Colombo
| Letters to the Editor ‘Letters to the Editor’ should be brief and to the point. ‘Letters to the Editor or editor@sundaytimes.wnl.lk. |