Dengue Epidemic: Back to basics to prevent spread


I was alarmed by hearing that in the first four months of this year there have been over 39,000 dengue patients hospitalized. There may be thousands more who were treated by General Practitioners. This number is usually what we have in a year and not four months! Colombo city itself has a 100% increase with over 2000 patients.

It is pertinent to look into the causes of this massive outbreak. In the 1990s, Dengue fever was mainly in Colombo city and the suburbs. Colombo city had around 300 during the whole year. Last year this number was ten times higher. Even in the country, the numbers rose to around 40,000. But this year, in four months it has reached that number.

From Colombo Dengue spread along the railroads, bus routes and made pockets of dengue outbreaks where the roads or tracks ended. If one goes back and studies what happened since 1990s, you will find that new pockets were created in Matara, Puttalam, Kurunegala, Kandy etc. Most of the outbreaks were the result of people traveling from those areas taking the disease back to those areas. It is not only the patients who are ill with dengue fever that took the disease to the periphery, but also the Aedes (dengue) mosquitoes who traveled along with them in the railway carriages or buses. The train carriages were virtually parked in jungles between Maradana and Fort. It was only when the city development was happening during 2010-2014 period that these jungles were cleared, although we had a running battle earlier with the CTB and Railway authorities trying to get the land areas bordering the St Sebastian canal cleared. The railway passengers themselves contributed to the spread, as when the trains were reaching the stations they were in the habit of throwing out the waste, which included yoghurt cups, plastic bottles, shopping bags etc, which disappeared in the tall grass which lined the railway track. So once it rained, water collected and the grass gave enough shade so that the water never fully evaporated due to sunlight, and dengue mosquitoes laid their eggs safely.

The other mosquito breeding places were large land parcels owned by public institutions and private residences, especially in Colombo 7, where the garden spaces were never ecologically managed. So were the schools and hospitals. To make things worse all the patients in the country ended up in Colombo making it a hospital city, until the adults were sent to Angoda for specialized care. Still, the Lady Ridgeway Hospital takes care of the serious child patients. There are many other private hospitals in the city which are also creating a hazard when it comes to dengue epidemics.

Dengue control and prevention is a duty of the local authority. The Public Health Department of the Colombo Municipal Council has a cadre of 1200: it should have around 55 Public Health Inspectors, 150 Midwives, 185 Health instructors, 55 Mosquito control Field Assistants, who could have been used to inspect all the premises and land parcels in the city which number around 80,000. Unfortunately, instead of these 450 Field Officers, we had only around 180 to do this work. Unfortunately, all my requests to fill the vacancies fell into deaf years at the CMC and also the Provincial Council. We still managed to use volunteers to join them and allocated areas to each officer, who was responsible for inspections and prevention of the spread of dengue in the area allocated to him. To supplement this work and to overcome the shortage of workers, we purchased Ultra Low Volume (ULV) machines, Fogging machines, spraying cans and used chemicals such as BTI, deltamethrin to spray against mosquito breeding or to get rid of adult mosquitoes. We sprayed the gabion walls, which lined the canal system in Colombo with BTi. These mosquito control programmes started at 5 am daily and ended around 7 pm. It was done according to a plan and covered the whole city operating from six administrative areas and centrally. We conducted the Green Star house-to-house inspection programme, which was an innovative idea at that time, winning an international award and also published as a ‘Best Practice’ by UNCHS and WHO.

Unfortunately, all these programmes have been stopped due to some unknown reason. Only the interiors of houses are sprayed, when 95 % of the breeding takes place outside the four walls. The PHIs in the suburbs also have copied Colombo’s above idea, and this may be one reason why we have so many dengue mosquitoes and patients today. Even the inspections have been done only when Mosquito control weeks have been announced by the Ministry of Health. Police and service personnel have been deployed to help, but it is not an efficient way of handling the situation. So what should we do now?

1) We must have dedicated staff (2 officers with at least 2 volunteers) say for around 50-75 premises in a street, who will meet the residents, create awareness and check these same premises and lands throughout the year. They will know exactly where to look for mosquito breeding in their allocated area, as it is difficult to find the larvae which could breed in one teaspoon full of water. "Detect & Destroy" should be their motto. This is far better than sending officers to unknown terrain to look for breeding spots which will be fruitless.

2) All vacancies for PHIs, Midwives, Health Instructors and Field Assistants should be filled immediately. There are enough A/L qualified youth who could fill these vacancies easily. This will enhance the capacity of the dengue control team. There may be vacancies for Solid Waste Management Overseers in The Municipal Engineer’s Department, who also could be co-opted for this work as waste is one of the main contributors for dengue mosquito breeding.

3) The stopped chemical/BTI spraying programmes should be re-started. The internal spraying should be stopped as that strategy is used in Malaria control where the mosquitoes rest inside the houses. This internal spraying will cause more harm than good as the residents will be breathing the chemicals and that could create respiratory diseases, and also the food could be contaminated.

4) The shramadana programmes of yesteryear should be re started as soon as the waste dumping issue is settled in the country. This is very important in slum and shanty areas in the city, where 60% of the city’s population live.

5) All yards and bus stands, where public transport vehicles are parked, should be fumigated and kept clear of mosquito breeding places.

If we do the above mentioned things and keep the city clean I am sure we can prevent the spread of dengue from Colombo to other parts of the country. One must not forget that most of the permanent residents of Colombo, by now, would have been victims of dengue even without their knowledge as dengue fever can pass off as an ordinary fever. A study done in Wanathamulla a few years ago showed that 95% of the children below 5 years of age had dengue antibodies in their blood, showing that they had already contracted dengue. This means they have immunity against the dengue virus circulating at that time. But in the distant and virgin areas and towns, the people would not have come into contact with the dengue virus yet and they are prone to going down with the disease easily.

The Ministries of Health, Housing, Urban Development & Transport, the Western Provincial Council and the Colombo Municipal Council should get together to implement the above programme.

Dr. Pradeep Kariyawasam

Former Chief Medical Officer of Health, Colombo.

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