Mosquito Viruses


Mosquitoes Can Carry Viruses

In Krabi you might come across mosquitoes carrying viruses that affect humans.

The two most common viruses are Dengue (hemorrhagic fever) and Chikingunya. Neither virus is infectious—it cannot be transmitted from person to person. Both are caused by daytime mosquito bites from infected mosquitos—
Aedes aegypti and Aedes albopictus.

When going into forested or jungle areas, use a strong insect repellant (DEET ingredients).

Symptoms of dengue are:

  • High fever (40°C/ 104°)
  • Severe headache
  • Pain behind the eyes
  • Nausea, Vomiting
  • Swollen glands
  • Muscle and joint pains
  • Rash

For any of these symptoms, a person should see a doctor. The incubation period for dengue is 4 to 7 days (but in some cases takes up to 15 days). Initial symptoms are a severe headache, low backache, chills, a fever, and leg aches (like the flu). In most cases, this will be followed by a large red rash somewhere on the body. The aching will get worse. Dengue is sometimes called break-bone fever or bonecrusher disease because of this pain.

Treatment includes drinking lots of liquids, keeping body temperature down, and pain relief (aspirin can make symptoms worse—check with a doctor). The virus needs to work its way out of the system and like most viruses cannot be directly treated. In the month following dengue, it is common for a person to suffer a mild depression.

Occasionally, the dengue may get worse 3-7 days after the first symptoms in conjunction with a decrease in temperature (below 38°C/ 100°F). The new symptoms include:

  • Severe abdominal pain
  • Persistent vomiting
  • Rapid breathing
  • Bleeding gums
  • Blood in vomit
  • Fatigue, restlessness

At this point, dengue can become very serious and requires careful medical supervision.

Chikingunya is similar, except the joint pain last longer and the fever can go higher.
Symptoms appear between 4 and 7 days after the patient has been bitten by the infected mosquito and these include:

  • High fever (40°C/ 104°F)
  • Joint pain (lower back, ankle, knees, wrists or fingers/toes)
  • Joint swelling
  • Rash
  • Headache
  • Muscle pain
  • Nausea
  • Fatigue

Although painful and debilitating, chikingunya is not dangerous to healthy adults. Most problems occur in very young children and older, infirm people.


Malaria is rare in Krabi, but not unheard of.

Malaria is contracted from an infected mosquito at night—from dusk to dawn.

Symptoms will usually show up seven days or more (usually 10–15 days) after the infective mosquito bite. The first symptoms, which may be mild—fever, headache, chills and vomiting—are similar to many other virus illnesses and are difficult to recognize as malaria.

Visitors who are traveling to malaria regions of Thailand should consult with their doctor about the best preventative medicine to take. Some of these need to be started two weeks in advance of travel.

Malaria Areas for Thailand & Region
Malaria Carrying Mosquito
Bites from Dusk through Dawn
Denque Carrying Mosquito
Bites from Dawn to Dust (Daytime)