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Sunday October 31, 2010 MYT 12:00:00 AM
Friday November 22, 2013 MYT 3:56:40 PM
by lim wey wen AND loh foon fong
The battle to reduce the incidence of dengue fever must be fought on various fronts.
DESPITE the headline-grabbing and often alarming nature of dengue outbreaks, there are a few reasons why dengue is still considered by the World Health Organisation (WHO) as a “neglected disease”.
It is currently the fastest growing mosquito-borne disease in the world. Yet, limited national and international funding have hampered dengue control activities, including efforts to control the population of Aedes mosquitoes that transmit the disease, and the development of an effective vaccine, treatment, or cure to help those already infected.
But unlike its other counterparts listed under the “neglected tropical disease” column like leprosy or cholera – which are “neglected” or “forgotten” because it affects almost exclusively the poorest and most marginalised countries – dengue is a problem experienced worldwide.
However, it is often the victim of distraction and habitual fire-fighting: our tendency to always deal with a problem at hand and moving on quickly to the next without examining it long enough to find sustainable solutions.
The magnitude of the problem
Speaking to The Star at the sidelines of the 61st WHO Western Pacific Regional Committee session two weeks ago, WHO regional communicable diseases expert John Ehrenberg described the situation: “Governments are only paying attention to dengue when there are outbreaks. And in the reactive mode, very little attention has been given to dengue in between outbreaks.”
At the heart of this tendency was the impression that the problem of dengue is not as serious as it seemed to be. As surveillance systems in the past were patchy and documentation of dengue cases in countries and regions were poorly coordinated, the magnitude of the problem was not fully comprehended.
“We just didn’t understand the magnitude of the problem, until we are hit by an outbreak,” says Ehrenberg. “Only now, when we are able to trace and follow countries that are reporting more regularly to the WHO, we have a far better idea,” he says.
In the past decade, reported dengue cases in the WHO Western Pacific region (in which Malaysia is a member) have doubled. From the 100,000 cases reported in the region in year 2001 to 2002, the region has seen over 200,000 cases since 2007.
Last year, there were 242,424 dengue cases and 785 deaths in 25 out of the 37 countries in the region. The countries that were hardest hit included Cambodia, Malaysia, Philippines, and Vietnam.
“We had a very bad outbreak in 2007 in Cambodia, some very serious outbreaks in the Pacific (Islands) in 2008; the Caribbean was quite badly affected this year, and we’ve had outbreaks in the Philippines, Laos, and even countries such as Singapore, which have, in many ways, set the standard for the inter-sectoral collaboration that have been effective in battling dengue,” says Ehrenberg.
On top of the increasing frequency and intensity of which these outbreaks occur is the spread of the Aedes aegypti mosquito to areas it did not previously inhabit, like the United States, the Northern Islands of Japan, and the Pacific Islands.
While the Northern Islands of Japan is still free from dengue, the spread of dengue to the United States and some countries of the Pacific Islands have proven that once the vector of disease is present, there is a potential for the disease to spread.
“So I think the issue of raising the red flag to dengue and saying that a lot of attention has to be paid to it is the right message. But the message should not be directed just to the WHO, it’s a message that (says) governments should also take very clear cut responsibilities too,” says Ehrenberg.
It is everyone’s problem
In the Western Pacific region, member states are starting to look into implementing the strategies included in the Dengue Strategic Plan for the Asia Pacific Region (2008-2015), which includes strengthening national dengue and vector surveillance systems, and improving healthcare workers’ capacity to detect dengue early and manage them correctly.
Cambodia, the Lao People’s Democratic Republic, and the Philippines have started to look into using guppy fish and jar covers to control and reduce the breeding of Aedes mosquito, and back home, the Malaysian National Strategic Plan for Dengue Control involves building a strong dengue surveillance system, providing guidelines on dengue case management, disseminating information about dengue to the public, and enforcing penalties on those whose premises are found have Aedes mosquito breeding sites.
Nevertheless, these regional and national strategies on dengue could only work when there is cooperation from all sectors of governments and the whole of society.
“In many ways, many of the factors that contribute towards dengue outbreaks are beyond the control of the Ministry of Health. In responding to a dengue outbreak, all agencies need to be involved,” says Health Ministry director-general Tan Sri Dr Mohd Ismail Merican via email.
For instance, in Malaysia, when an outbreak occurs, a district dengue outbreak committee is formed to ensure that all other agencies – from the town council to the village committee – fulfil their roles in maintaining sanitation and encouraging the community to participate in anti-dengue activities such as gotong-royongs to clean their compounds.
“Fogging alone does not stop an outbreak,” says Dr Ismail. But source reduction (the reduction of Aedes breeding sites) can.
As spraying the affected area with insecticides will only kill adult mosquitoes, the larvae and eggs left by mosquitoes will continue to grow into adult mosquitoes days after fogging. Furthermore, these new mosquitoes do not always need to bite an infected human to transmit the dengue virus. Infected mosquitoes can pass on the dengue virus via their eggs for as long as six generations!
“As such, fogging is only to buy time – time to search and destroy breeding places after we initially kill the infected mosquitoes,” says Dr Ismail. And as the Aedes mosquito, which insect experts and fumigators sometimes call the “high-class” mosquito, lives predominantly in urban areas and only in water containers holding clear water, these breeding places are mostly found in houses, shops, and waste disposal areas.
“Although it is the job of the Health Ministry and the local authorities to check houses and clean up drains and roadsides, neither one have enough manpower to inspect all the houses in Malaysia, or clear the garbage that is thrown inconsiderately in the drains and by the roadside.
If the public can help us keep their house and surroundings clean, we can immediately remove 73% of the breeding sites, says Dr Ismail.
And it is here to stay
Unfortunately, without a vaccine, or even a treatment or cure, it is highly unlikely that the world would be able to rid itself from dengue at this point, says Ehrenberg.
Reducing the impact of outbreaks and the number of deaths is therefore key to dengue control. In simple words, Ehrenberg explains, “If I can’t prevent my wife from getting sick with dengue, I can take her to the hospital in time and then prevent her dying from a dengue haemorrhagic episode.”
This starts with the awareness that dengue is a disease that has many faces. In some, it may cause a mild fever and flu-like symptoms that could be easily confused with a whole list of other fever-inducing diseases. In others, it might be a textbook case of dengue – complete with high fever, headaches, red spots, and muscle and joint pains that gives it the name “bone-breaking disease”.
There is also no way to tell whether someone will or will not develop dengue haemorrhagic fever (when blood vessels are damaged and they start to bleed from their nose, gums, or under the skin) and dengue shock syndrome (when there is massive bleeding from within).
“It does not go by the book,” says Ehrenberg. That is why since year 2008, WHO dengue experts have started to propose a simplified classification of dengue to replace the current classification of the disease into dengue fever, dengue haemorrhagic fever, and dengue shock syndrome.
The new classification, which is being gradually adopted by countries worldwide, will classify all dengue cases into either dengue or severe dengue, and is expected to be more flexible in dealing with the various manifestations of the disease. (See In the pipeline.)
“Dengue does not just affect the blood vessels. It affects the liver. It can go to the brain. You can also have many other manifestations that are usually left out under traditional dengue case classifications,” says Ehrenberg. “The new classification system will give clinicians and caregivers much more elements to consider so that they would be able to detect a wider range of individuals that do have dengue.”
As the search for an effective vaccine and treatment for dengue is still ongoing, early detection (to reduce deaths) and vector control is still the main tool in dengue control. This means, instead of letting healthcare workers shoulder a large part of the responsibility to control the dengue epidemic, individuals and members of communities also need to play their part in reducing mosquito breeding sites.
“If we fail to control dengue, it is because we failed as an individual to get rid of breeding places inside and outside our house; as a community for not keeping our area clean and not achieving source reduction, and as the local authority for not being able to keep our drains and public areas clean,” says Dr Ismail.
In the pipeline
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