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Dengue Virus: About

An airplane flies above the sea at sunset

Dengue is an illness spread by the bite of infected Aedes aegypti and Aedes albopictus mosquitoes.

Cases of dengue in Wisconsin residents occur in people who have traveled to tropical or subtropical regions with a high risk of dengue, including the Caribbean, South and Central America, Asia, and parts of tropical Africa. Dengue is very rarely spread in the U.S.; however, there have been outbreaks in Florida, Texas, Hawaii, Guam, and Puerto Rico.

Anyone who travels to areas where dengue is spread can get the illness, but people who spend more time outdoors are at a higher risk of being bitten by an infected mosquito. It is important to take preventive steps when traveling to areas with dengue virus, such as wearing protective clothing, using insect repellents, and using mosquito netting.

For more tips, please visit our Mosquito Bite Prevention page. For country-specific travel information and recommendations, visit the CDC (Centers for Disease Control and Prevention's) Travelers' Health page.

Dengue is spread to humans through the bite of an infected mosquito.
  • Mosquitoes get infected with dengue by feeding on humans that have been infected with the virus.
    Mosquito drawing blood from skin.
    • After about one week, the virus may end up inside of the mosquito.
    • Once it has the virus, a mosquito may spread the virus to uninfected humans when it takes another blood meal.
    • Sick people can carry the virus in their blood a few days before symptoms develop and during the first week of infection when they have a fever. If they are bitten by an uninfected mosquito, they can transmit the virus to to the mosquito, continuing the cycle.
  • The mosquitoes that spread dengue are most active during the daytime. Peak biting hours are early in the morning and in the evening before dusk.
  • It is possible to get infected with dengue from organ transplants or blood transfusions from infected donors, or from mother to fetus during pregnancy. These cases are rare.

Dengue is preventable. Visit our Mosquito Bite Prevention page to learn how to prevent mosquito bites.

Symptoms usually show up four to 10 days after being bitten by an infected mosquito.

Most people (about 75%) infected with dengue never develop symptoms. Those that become sick may develop severe flu-like symptoms, and recover after about one week. However, some people may develop a severe form of dengue, also called dengue hemorrhagic fever, or dengue shock syndrome. When this happens, the person develops warning signs of severe complications three to seven days after the first symptoms appear, right after the fever has started to decrease. It is important to go to an emergency room immediately if any of the warning signs appear. Severe dengue can cause shock, internal bleeding, and death.

There are four different kinds of dengue virus, so past infection with dengue will not always make you immune to the virus in the future. You will only be immune to the type of virus that infected you in the past.

First signs and symptoms:
  • High fever
  • Severe headache
  • Severe pain behind the eyes
  • Muscle aches and/or bone pain
  • Joint pain
  • Rash
  • Mild bleeding (nose, gums, purple spots under the skin, easy bruising)
  • Low white blood cell count
Severe dengue warning signs and symptoms (usually 24-48 hours after the fever goes away):
  • Severe stomach pain or persistent vomiting
  • Red spots or patches on the skin
  • Bleeding from the nose or gums
  • Vomiting blood
  • Black, tarry feces
  • Drowsiness or irritability
  • Pale, cold, or clammy skin
  • Difficulty breathing

There is currently no treatment or vaccine for dengue.

Over-the-counter pain relievers, such as Tylenol, may be given to relieve the symptoms. Do not take aspirin or ibuprofen, as they can increase the risk of bleeding. It is important to get plenty of rest and drink fluids. In severe cases, patients may need to be hospitalized to receive supportive treatment.

If you or a family member has recently traveled to an area with dengue, and believe you may have dengue virus, contact your doctor.


CDC resources

Dengue is preventable. Visit our Mosquito Bite Prevention page to learn how to protect yourself from illnesses spread by mosquitoes.

Questions about illnesses spread by mosquitoes? Contact us!
Phone: 608-267-9003 | Fax: 608-261-4976

Last revised April 26, 2023