Eliminating dengue: What does it take?

By Fathima Riznaz Hafi

​Dengue has gone beyond control with an exponential rise of cases and no sign of decline. Many attempts have been made to bring the situation under control but with the dengue cases and mortality rates continuing to rise, National Hospital of Sri Lanka Consultant Cardiologist Dr. Gotabhaya Ranasinghe points out that the inability to bring the epidemic under control is due to current strategies not working and he therefore proposes a strategy that he says would be key to eliminating the disease altogether. 

In an interview with Daily FT he explained, “There’s a missing link in the dengue control methods; current methods are not working; dengue cannot be eliminated until we come up with the right strategy.”

Though a cardiologist, Dr. Ranasinghe has had an interest in dengue since he was an intern back in 1991 and was one of the first doctors in the country who studied dengue. It was during that period that they had noted the relationship between dengue and monsoon rains. He continues to study the situation and now proposes a strategy which was inspired by the ground-breaking strategy that had eliminated the Ebola epidemic. 

“We should learn from the Ebola epidemic in West Africa. Ebola is a highly contagious disease that is spread by contact unlike dengue which is spread by mosquitoes. The Ebola epidemic took place two years ago; it spread very fast and mortality was very high but still they controlled it! The way they controlled it was by ‘isolation’ – strict isolation! No one – not even WHO thought they would control this epidemic so soon but they did – through very strict isolation of the patient – and nothing else. Therefore in our case, I propose the strict isolation of the dengue patient is the solution! That is the centre of dengue control.”

How it works

He explains that though dengue is spread by the Aedes aegypti mosquito, that doesn’t mean that all of them carry the dengue virus – only those who have bitten a person infected by dengue get infected and then spread the infection to healthy people when they bite them. The other aegypti mosquitoes are not infected and therefore do not spread dengue when they bite.

Further, if one particular mosquito bites a dengue patient, it will remain infected till its death and that would be for about one month as its lifespan is a month. Before that mosquito dies, within that month, it bites many people because it needs a blood meal and in this process infects them all. 

“So if we have 100 infected mosquitoes like that, these 100 will go all over the place biting people and the most important link here is – if you prevent the mosquito biting the patient – and that infected mosquito then biting the normal person – we have our answer. The best way to prevent dengue is by preventing the non-infected mosquito from biting the infected person and then biting a healthy person. At the moment we have a large number of dengue patients in the country. If we isolate every patient (strict isolation with net, repellent, etc.) for a certain period, even if there are a million mosquitoes in the environment, they won’t get infected.

“Through isolation, normal mosquitoes won’t bite the patients and get infected; therefore the population of dengue mosquitoes will be less. But there are still those mosquitoes that have already been infected with the virus and are out in the environment, biting and infecting healthy people.  Then those people get dengue – we isolate them too ... it goes on like that. 

“The remaining mosquitoes will still go around biting – but for how long? The maximum they can go for is one month – then they die. After one month we can slowly see the numbers reducing. In the meantime, to protect ourselves, we should use repellents, especially during early morning and late evening which is when the Aedes mosquitoes are active. There are many good repellents to choose from!” he said. 

Field hospitals

When asked how he proposes the isolation of such a large number of patients, considering the lack of space in hospitals to accommodate the overwhelming numbers, he again referred to how the Ebola epidemic was contained. “They had the ‘field hospitals’ (mobile hospitals); they put up tents outside and acquired empty buildings and from there they controlled; that’s how we should do it; we can get hold of warehouses too,” he said. 

Isolation may be a good strategy and isolation of adults is fine but what about children? They will need their mothers with them – otherwise they would be terrified. How can we separate them? To this he replied, “During Ebola they had to separate them because the mother could also die but with dengue we don’t have to do that. The mother can stay with the child and she will probably get infected too in which case she will be isolated as well until the infection is gone. The isolation period is not long – it will be for as long as the infection lasts in the patient, which is around 12 days. With Ebola it was weeks and months.”

Why current strategies aren’t working

“Right now we are trying to remove the whole mosquito population by destroying the breeding grounds. By doing that we think we kill millions and millions of larvae and thereby reduce the population of Aedes mosquitoes. We are trying to eliminate an entire mosquito population – can we do that? I’m not against the control of breeding but it’s a huge task,” he says. 

“Posters are sent out telling us to remove water from pots and gutters, etc. You remove yoghurt cups and plastic bags and a few months later, people put them there again. Then again water collects and again we get the mosquitoes. It’s practically impossible to control. 

“Also, by destroying the mosquitoes, we are creating an imbalance in the environment. These mosquitoes may be needed to complete a cycle – we could create new problems in the environment. Even with Ebola they never went around killing monkeys (which caused the virus); they caught the tail – which is the patient.”  

He added, “We have to think about this: If we are controlling the situation successfully by destroying the breeding grounds, why are numbers going up?” 

The easiest way  

“The easiest way to eliminate dengue is to prevent the mosquito biting the patient, through isolation! If that mosquito never gets infected, even if it bites 100 people there’s no dengue! This is very difficult to convince people because they are brainwashed to control the larva. I think it is this link that people have to concentrate on; it’s very easy, costs less and you only have to do it for a few months; if you choose to destroy breeding grounds you have to keep doing it,” he said.

Dr. Ranasinghe concluded noting that isolation may initially seem difficult and one may wonder if this is possible, with issues such as space but asserts that if we follow the Ebola strategy and go for field hospitals, after the isolation is implemented, we can see that eventually the cases will decrease. The deadly disease Ebola was eliminated through strict isolation and the use of field hospitals; therefore he strongly believes that we can eliminate our deadly disease dengue too if we follow their example.