Tackling the source of infection is the science of outbreak control but the challenge is identifying it.
“It can be at work, at home or anywhere the patient has stopped along the way,” he said in response to calls from experts to trace dengue infection epicentres to bring down the number of dengue cases.
Former Malaysian Association of Environmental Health vice-president S. Veeramohan and World Health Organisation Collaborating Centre for Arbovirus Reference and Research director Prof Dr Sazaly Abu Bakar both believe that it is important to examine the route individual patients take to learn the location and source of infection.
Dr Chong agreed to this need but said the challenge is in tracing it back for about 14 days as the dengue incubation period is four to 10 days and another two to three days when patients fell ill.
“An Aedes mosquito can fly up to 400m and that means, if you pass by a row of shops every day, the mosquitoes can be in any of the shop houses in that row or behind or in front of the row of shophouses up to 400m, making it hard to track down,” he said.
The ministry was looking forward to new ideas of using vaccines and the Wolbachia bacteria, he added.
According to the ministry, the current process of investigating cases include requiring each dengue case reported to the ministry to be investigated by the health environment officers, who will look into the patients’ movement or places which he/she has visited within two weeks before the onset of dengue.
The officers are to get history of family members/office mates/ schoolmates/close friends who are also infected.
They will also do an Aedes survey at all the places that are a potential source of infection. This information will then be analysed by the public health physician at the district health office for control measures to be carried out at the most probable source of infection and it will be done within 24 hours after the case is reported.
Moreover, the ministry said to identify mosquitoes that carry the virus, a special test is required for hundreds to more than 1,000 mosquitoes to be captured before one or two are found to carry the virus.
Meanwhile, former deputy Health director-general Prof Datuk Dr Lokman Hakim Sulaiman said before his retirement from public service in 2017, he used to allow new ideas on dengue control to be tested.
He said the idea of targeting infection epicentres instead of residential homes and offices was encouraged but the method should be published in journals for others to assess.
He also said health departments had tried to locate the source of infection but the hotspots were too many.
Dr Lokman also pointed out that dengue is a vector-born disease and there are four elements that can bring about transmissions, making it difficult to control the disease.
Littering is still a big problem and people are not using repellents when going out in the early morning or late evening, he said.
“Research and development is still lacking and dengue remains a neglected disease globally,” he added.
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