Dengue 

Page originally published 7/25/2024. Page last updated 10/25/2024.

Close-up photo of Aedes mosquito (small, dark in color, and white markings on bodies and legs).

Dengue (den-gee) is an infection caused by the dengue virus. Dengue is spread by infected mosquitoes. The mosquitoes that spread dengue (Aedes aegypti and Aedes albopictus, also called “Aedes mosquitoes”) live in many parts of the world including the United States, and in California and San Diego County.

Dengue is commonly seen in Africa, the Middle East, India, Southeast Asia, South America, Central America, and North America (specifically, Mexico). According to the World Health Organization (WHO), almost half of the world’s population, 4 billion people, live in areas where dengue infection occurs. Cases of dengue happen during mosquito season, which starts in the summer and continues through the fall but is a risk all year in tropical parts of the world.

Dengue is not common in the United States. In San Diego County, dengue cases are reported every year in travelers returning from countries where dengue cases are locally spread. Globally, the number of dengue cases has reached the highest level ever. This means that travelers have an even greater chance of getting dengue. Travelers can lower their risk of getting dengue by taking steps to prevent mosquito bites. There have been a number of dengue cases in San Diego County in people returning from travel to the countries listed above. About half of the world’s population is at risk of dengue virus each year.

See below, or click the following links, to learn more about:

Prevention

The best way to  prevent dengue is to protect yourself from mosquito bites.

Plan for Travel:

  • During your stay
    • Follow steps to prevent mosquito bites to protect yourself and your family.
    • Stay in places with air conditioning and with window/door screens, when possible.
    • Use a bed net if air conditioned or screened rooms are not available or if sleeping outdoors.
    • Wear long-sleeved shirts and pants.
    • Treat clothing and gear with insect repellent.
    • See a healthcare provider if you develop a fever or have symptoms of dengue.
  • After your trip
    • Even if you do not feel sick, travelers returning from an area with risk of dengue should take steps to prevent mosquito bites for 3 weeks so they do not spread dengue to uninfected mosquitoes that could spread the virus to other people.
    • See a healthcare provider if you develop a fever or have symptoms of dengue. Tell your provider about your travel.

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Transmission (Spread)

Dengue is usually spread to people by the bite of an infected mosquito. Mosquitoes become infected when they bite a person infected with the virus. After about a week, the mosquito can spread the virus to other people it bites. Dengue virus is not spread from person to person.

After getting bitten by a mosquito with dengue virus, symptoms may develop within 2 weeks. People can get infected with dengue more than once in their life. 

In a very small number of cases, dengue virus has been spread through exposure in a laboratory or healthcare setting; mother to baby during pregnancy, delivery, or breast feeding; blood transfusion; organ transplant; and needlestick injuries. Blood banks and organ transplantation centers routinely test for dengue to prevent  spreading the infection.

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Symptoms

Illness from dengue virus typically lasts 2-7 days. Most people recover after about one week.

About 1 in 4 people infected with dengue virus will get sick. For people who get sick, symptoms can be mild or severe.

The most common symptom of dengue is fever. Other symptoms include:

  • Headache;
  • Pain behind the eyes;
  • Muscle, joint, or bone pain (dengue is sometimes called "break-bone" fever because of the high level of bone pain it causes);
  • Nausea;
  • Vomiting; and/or
  • Rash.

About 1 in 20 people who get sick with dengue will develop severe dengue. Severe dengue is a medical emergency. It can rapidly worsen into shock, internal bleeding, and death in a few hours once the warning signs begin. Go to a local clinic or emergency room immediately if you or a family member have:

  • Stomach pain or tenderness;
  • Vomiting (at least 3 times in 24 hours);
  • Rapid breathing;
  • Bleeding from the nose or gums;
  • Blood in vomit or stool (poop); and/or
  • Feeling extremely tired or restless.

These warning signs usually begin 24-48 hours after the fever has gone away. People who have had dengue before are at greater risk of severe dengue illness

For infants, watch for signs of dehydration, which include urinating (peeing) less frequently; dry mouth, tongue, lips; few or no tears when crying; and sunken soft spots of the head or eyes. If these symptoms appear, contact your child’s pediatrician immediately. If severe dehydration occurs, which includes sleepiness and lack of energy; sunken eyes; cool, discolored hands or feet; and only pees 1-2 times a day, then go to an urgent care or the emergency room  immediately .

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Diagnosis and Treatment

If you think you may have dengue, talk with your healthcare provider. Your healthcare provider may:

  • Ask about your signs and symptoms,
  • Ask you if you traveled and were bitten by mosquitoes, and
  • take a blood sample to be tested.

There are no antiviral medicines available to treat dengue illness. Antibiotics do not treat viruses. Rest, fluids, and over-the-counter pain medications may relieve some symptoms. In severe cases, patients may need to be hospitalized to receive supportive treatment.

  •  Note: For pain and fever medications, take acetaminophen. Do not take aspirin or ibuprofen.

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