Dengue Fever &
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A blog post on the dangers of chemical fogging to eradicate mosquitos
Dengue or "break-bone" fever is a relatively common problem in Jakarta and is a viral disease found in the tropics and sub-tropics. It periodically reaches epidemic proportions in Indonesia (usually every 4-5 years). However, it is rarely fatal in healthy and fit individuals, although the patient is often left debilitated and requires a considerable period of time for convalescence. Dengue fever is most common during the rainy season (November-May) as Aedes mosquitos require clean standing water to reproduce. The peak of the season is usually from March through May.
Dengue occurs is spread by mosquito bites and is due to the infection by a flavivirus which is transmitted by the bite of the Aedes aegypti mosquito. This mosquito bites during the daytime. Unlike malaria, this disease is present throughout the greater Jakarta area, and dengue fever has been reported in nearly all major cities of Indonesia.
There is no vaccine against dengue fever, though several are in development. Wear long sleeves and long pants, and use insect repellents to prevent mosquito bites.
Particularly in the first stages of illness, dengue fever is difficult if not impossible to clinically distinguish from the many other possible causes of similar symptoms and signs.
For adults, the infection progresses as follows:
Following an incubation period of 2-14 days, the onset of symptoms is usually abrupt with chills, high fever, severe headaches, backaches, weakness, pain behind the eyes, and lassitude often reported. Joint, muscle, and back pains can be very painful, creating the reason behind older name 'breakbone fever'. Fevers may reach 40°C (104°F), and the victim's heart rate and blood pressure often drop.
During the 2nd to 6th day of infection, nausea and vomiting may occur, and the patient may develop one or more of the following; skin hypersensitivity, generalized swelling of lymph nodes, swelling in the palms, changes in taste sensation, loss of appetite, constipation, anxiety or depression.
Two to four days afterwards, temporary improvement may occur with a sudden drop in body temperature and subjective improvement over 24 hours. Then follows a second rapid temperature rise and the appearance of a characteristic rash on the trunk, limbs, palms and soles. The skin in these areas turns bright red, may peel and often blanches under pressure. Recovery afterwards is slow and convalescence can take weeks. Bed rest, antipyretics and analgesics are often required.
Epistaxis (“nose bleeds”), petechiae (“red skin spots”) and purpuric skin lesions (“purple skin spots / bruises”) can occur at any stage of the disease, varying with age, sex, and type of dengue virus. Bleeding from the gastrointestinal tract, and excessive vaginal bleeding if menstruating can also occur, but do not usually occur in the majority of cases.
For children, the infection progresses as follows:
A fever occurs in nearly all dengue infections in children. Other common symptoms are a red throat, a (usually mild) runny nose, cough, and mild gastrointestinal symptoms similar to pharyngitis, influenza, and upper respiratory infections. The presentation of dengue in the younger child is much less clear-cut than in adults.
The acute illness can last up to ten days, but complete recovery can take two to four weeks.
Confirming the diagnosis
There are no immediately useful or unequivocally accurate tests for dengue fever. However, there are indicators that can be used to confirm an initial diagnosis of dengue fever:
Definitive confirmation of dengue infection can be accomplished through sophisticated tests which take two weeks or more after the onset of the illness to be processed. For the test(s), two separate blood samples need to be tested by the same lab for dengue antibody levels. Needless to say, these tests are not often performed.
Dengue hemmorhagic fever (DHF) and dengue shock syndrome (DSS)
A rare complication of dengue fever, DHF occurs most often in small children and elderly adults. If DHF occurs, it will usually do so by day 3-5 of infection. The relationship between DHF and previous dengue infection has not been clearly established, but previous exposure to dengue is correlated with subsequent DHF. Uncontrolled bleeding distinguishes DHF from fever accompanying a dengue infection. Bleeding can occur from the gums, nose, intestine, or under the skin as bruises or spots of blood, especially under a tourniquet. The liver is often enlarged. The fatality rate is about 5%.
In children, the progression of disease is not always characteristic. A relatively mild first phase with an abrupt onset of fever, malaise, vomiting, headache anorexia and cough is succeeded 2-5 days later by weakness and, sometimes, physical collapse. Frequently, spots appear on the forehead, arms and legs, along with spontaneous bruises and bleeding from punctures where blood was taken. A seriously ill child may breathe rapidly and with considerable effort; the pulse may be weak, rapid, and thready. Almost all DHF patients have a positive “tourniquet test” (where a tourniquet or blood pressure cuff is applied and the skin demonstrates petechiae and/or bruising).
The WHO criteria for DHF are a platelet count of less than 100,000 and a haematocrit 20% greater then normal. Children with similar blood indicators should be hospitalized immediately and managed for potential DSS. The syndrome can be lethal, and requires rapid in-hospital management with assiduous correction and replacement of fluid, electrolytes, plasma and sometimes fresh blood/platelet transfusions. Mortality due to DHF and DSS ranges from 5-30% in the untreated Indonesian population, with the highest risk category being infants under one year of age.
There is no preventative treatment for the dengue virus. Its symptoms can and should be treated, but there is no medicine or commercially-available vaccine for the virus. Vaccine candidates are going through clinical trials in many countries, but a safe vaccination protocol is not expected for some time.
It has been suggested that DHF is more likely if the patient has previously been infected by dengue fever within the last 8-12 months, and that the likelihood of DHF relates to this previous "sensitization".
To avoid getting dengue fever or DHF, you must avoid getting bitten by day-biting mosquitos.
Convalescence can take weeks, and bed rest and antipyretics and analgesics are required. An attack produces immunity for a year or more, but only to the one of the four flavivirus strains responsible for the intial illness.
In an epidemic, the emergency control measure is mosquito insecticide applied outside by vehicle-mounted or portable ultra-low-volume generators a minimum of twice a day at ten-day intervals.
All varieties of mosquitoes breed in or near water that is stagnant or slow-moving. The importance of mosquitoes in transmission of disease makes adequate control of mosquito breeding sites very important, especially those close to human habitation.
In the long term, community education and participation are necessary to eliminate mosquito breeding sites, as mosquitoes usually fly less than one kilometer from where they are hatched. Over 50 diseases can be transmitted by the bite of infected female mosquitoes, such as malaria, dengue fever, Japanese B encephalitis, yellow fever, and a variety of forest and jungle fevers. Urban mosquitoes breed in any pools of standing water such as empty tin cans, old tires and water filled tire tracks, coconut shells, and the saucers under domestic pot plants. Rural mosquitoes breed in rice paddies, stagnant ponds and slow moving streams. Consquently, mosquito larvae can be eliminated or reduced by:
Treatment of mosquito nets with permethrin
Permethrin is available from Shell as a 20% emulsifiable concentrate (EC) and from ICI as a 50% EC (trade name Ambush). Experience has found that approximately 150ml of water is required as a wetting agent for 6 sq. m of mosquito netting.
A mosquito net treated in this way is effective for up to three months.
If you have medical-related questions about living in Indonesia to ask of medical professionals, see Ask the Experts.
We trust this information will assist you in making correct choices regarding your health and welfare. However, it is not intended to be a substitute for personalized advice from your medical advisor.
Our appreciation to Doctors Uwe Stocker and Rene de Jongh of International SOS, an AEA Company who has contributed this article in response to a growing health threat faced by expatriates in Indonesia.
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