What is Dengue Fever?

Dengue is a viral disease caused by any of the four related viruses: dengue virus 1, 2, 3, and 4. Dengue viruses are spread to people through the bite of an infected Aedes mosquito. A person can be infected with dengue multiple times in their life. The most common dengue symptoms are fever with aches and pains (eye pain, typically behind the eyes, muscle, joint, or bone pain) nausea, vomiting, and rash.

In California, almost all reported cases of dengue are in people who were infected by mosquitoes while traveling in other parts of the world. Currently, local transmission of dengue in California is very rare. Travel-related dengue cases have increased due to ongoing outbreaks around the world. In the United States, public health authorities in Puerto Rico declared an outbreak in March 2024. Additionally, U.S. Centers for Disease Control and Prevention issued a health alert advisory regarding the increased risk of dengue virus (DENV) infections in the United States in 2024.

Dengue is primarily transmitted through the bite of an infected Aedes mosquito, a mosquito now common in Southern California. Aedes aegypti mosquitoes are small (about ¼ inch), black and white, and feed almost exclusively on humans, biting aggressively all day long.

Monthly dengue reports can be found on the California Department of Public Health website.

Symptoms of Dengue

The most common symptom of dengue is fever with nausea, vomiting, rash, or aches in the eyes, muscles, or joints. To date, there are *no medical treatments for people suffering from this disease. Symptoms of dengue typically last 2–7 days. Most people will recover after about a week.

How residents can help reduce mosquitoes and prevent mosquito bites:

Dump and Drain Standing Water: Mosquitoes lay eggs in and near standing water. Mosquitoes only need a tablespoon of water to lay eggs. Potted plant saucers are the leading breeding source for the invasive Aedes aegypti mosquito. Limit the number of places mosquitoes can breed by dumping and draining items that hold water.

Wear insect repellent. EPA-registered ingredients such as DEET, picaridin, oil of lemon eucalyptus, or IR3535 (as directed on the product label).

Check window and door screens to prevent mosquitoes from entering your home.