While you might get malaria on vacation by going to coastal or forested areas frequented

by malaria mosquitos, you could get dengue fever during the daytime while at work.

The dengue virus, known as krun chim or "blood fever" in Khmer, is carried

by a very different mosquito from those that cause malaria.

Unlike the malaria mosquitoes which bite at night, Aedes aegypti-a domestic, urban

mosquito-bites during the day. They live inside and around houses and offices, laying

eggs in man-made containers such as water jars, ant traps, flower vases, discarded

auto tires, etc.

The dengue mosquito almost never breeds in ground water and rarely in wells. It also

has a very short flight range, with most flying less than 50 meters in their life

time. Aedes aegypti, a particularly beautiful mosquito, has silvery stripes on the

legs and silver spots on the side of the thorax.

Dengue is caused by a group of four closely related viruses we call DEN-1, DEN-2,

DEN-3 and DEN-4. These produce a range of diseases from simple Dengue Fever-or "breakbone

fever"-to severe Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome.

The symptoms of dengue fever are a rapid onset of a high fever, severe headache behind

the eyes, joint pain, and sometimes a rash. These symptoms develop about five days

after being bitten by an infected mosquito and last three to five days. Infection

by one strain induces immunity to that strain for life.

Problems occur, especially for children, when they become infected with a second

dengue virus strain between six months and five years after their first infection.

Instead of preventing infection by another strain, immunity actually enhances the

new infection and makes the disease worse.

In this case, just when the fever goes down the condition suddenly worsens, the

patient experiences profound weakness and restlessness, the blood capillaries begin

to leak, the patient bruises easily and may have small spots of hemorrhaging on the

skin.

In very bad cases there may be bleeding from the nose and gums and finally the intestines

and the patient may go into shock and die.

There are no specific drugs for dengue. Patients are provided with intravenous fluids

to keep them from slipping into shock. Aspirin can increase the bleeding so if you

suspect dengue, give paracetamol instead.

DHF is most serious for children. Cambodia (and Thailand) experience epidemics every

two to three years. The last bad one was in 1990 where there were more than 7,000

cases and 330 deaths.

Battambang has already had more than 150 cases and 15 deaths this year and in Phnom

Penh we are expecting another epidemic, either this year or next. The Ministry of

Health is launching DHF health education and control programs, so hopefully you will

be hearing a lot more about dengue and DHF soon.

In summary, to prevent being bitten by urban, daytime-biting mosquitos carrying

dengue:

• Eliminate breeding grounds around home and office by cleaning and covering water

  jars, and discarding tin cans, tires and broken jars.

• Put salt in ant traps, and change the water in flower vases at least once a week.
• Use repellents, especially on feet and ankles.
• Use mosquito coils under your desk.