Dengue Fever

Dengue fever is a mosquito-borne viral illness that affects millions of people each year worldwide, causing symptoms ranging from mild flu-like fever to life-threatening complications that require immediate medical attention.

breakbone fever, 7-day fever, dengue hemorrhagic fever, dengue shock syndrome

Table of contents

• What is Dengue Fever?
• How Dengue Spreads
• Where Dengue Occurs
• Signs and Symptoms
• Understanding Immunity and Reinfection
• How Dengue is Diagnosed
• Treatment and Recovery
• Prevention
• Dengue Vaccine

What is Dengue Fever?

Dengue fever is a viral infection caused by the dengue virus (DENV), which is transmitted to humans through the bite of infected mosquitoes^[1]. The disease is also known by various names, including breakbone fever or 7-day fever, reflecting both the severity and duration of symptoms^[6].

There are four different but closely related types of dengue virus: dengue virus type 1, 2, 3, and 4^[4]. About half of the world’s population is now at risk of dengue, with an estimated 100 to 400 million infections occurring each year^[3]. Most people who get infected with dengue have no symptoms or only mild illness. Research estimates that nearly 400 million people get infected with dengue each year, but most (about 80%) have no symptoms^[2].

How Dengue Spreads

Dengue viruses are spread to people through mosquito bites^[4]. The disease is primarily transmitted by female mosquitoes of the Aedes genus, particularly Aedes aegypti mosquitoes^[1]. Other Aedes mosquito species, such as Aedes albopictus, can also transmit the virus^[6].

When an uninfected female Aedes mosquito bites an infected person, the virus passes from human to mosquito and replicates inside the mosquito. Once infected, a mosquito can then transmit the virus to humans for the rest of its life^[16]. These mosquitoes are common in tropical and subtropical parts of the world^[6].

Dengue is not contagious from person to person in most cases, except when passed from a pregnant woman to their child^[2]. In rare cases, people can become infected through blood transfusions, organ transplants, or needlestick injuries^[16].

Where Dengue Occurs

Dengue is found in tropical and subtropical climates worldwide, mostly in urban and semi-urban areas^[3]. The disease is most common in Southeast Asia, the western Pacific islands, Latin America, and Africa^[1]. In the Americas, Aedes aegypti is the mosquito vector that is the main source of dengue transmission^[7].

Dengue transmission is common in over 100 countries in tropical and subtropical regions^[16]. In the United States, dengue frequently occurs in territories such as Puerto Rico, the U.S. Virgin Islands, American Samoa, and the freely associated states, including the Federated States of Micronesia, the Republic of Marshall Islands, and the Republic of Palau^[8]. Dengue infections have also occurred in the continental U.S., including in Florida, Hawaii, Texas, Arizona, and California^[16].

The disease has a seasonal pattern: most cases in the southern hemisphere occur in the first half of the year, and most cases in the northern hemisphere occur in the second half. This pattern corresponds to the warmer, rainy months^[7].

Signs and Symptoms

Most people who have dengue have mild or no symptoms and will get better in 1 to 2 weeks^[3]. Many people experience no signs or symptoms of a dengue infection. When symptoms do occur, they may be mistaken for other illnesses, such as the flu, and usually begin 4 to 10 days after being bitten by an infected mosquito^[1]. Symptoms typically last 2 to 7 days^[3].

If you do have symptoms, high fever (104°F/40°C) is typical, along with^[2]:

• Severe headache
• Pain behind the eyes
• Muscle, bone, and joint pain
• Nausea or vomiting
• Swollen glands
• Rash

Dengue is sometimes called “breakbone fever” because, in addition to fever, it can cause severe aches and pains, especially in the legs, joints, and back^[16].

Severe Dengue

In some cases, symptoms worsen and can become life-threatening. This is called severe dengue, dengue hemorrhagic fever, or dengue shock syndrome^[1]. About 1 in 20 people sick with dengue will develop severe dengue after their initial symptoms begin to fade^[2].

Severe dengue happens when blood vessels become damaged and leaky, and the number of clot-forming cells (platelets) in the bloodstream drops. This can lead to serious bleeding, dangerously low blood pressure (shock), and death^[1].

Warning signs of severe dengue usually begin 24 to 48 hours after your fever goes away and may include^[3]:

• Severe abdominal pain
• Persistent vomiting
• Rapid breathing
• Bleeding gums or nose
• Fatigue
• Restlessness
• Blood in vomit or stool
• Being very thirsty
• Pale and cold skin
• Feeling weak

People with these severe symptoms should seek care immediately^[3]. Severe dengue is a medical emergency^[2].

Understanding Immunity and Reinfection

You can get immunity to a version of dengue virus once you’ve been infected with it. Because there are at least four versions (strains) of the virus (DENV), immunity is complicated^[2].

Your immune system has tools it can use to recognize infections and get better at fighting them off. Antibodies are specific to each harmful invader to your body, fitting to them like a key to a lock. Once your body knows how to fight that specific virus, you are unlikely to get sick with it again^[2].

After getting one of the four strains of DENV, you shouldn’t be able to get that one again. However, you can be infected by other types of dengue virus^[16]. The antibodies for one strain don’t fit other versions quite perfectly. If you get infected by a different version of DENV later on, it can actually use this imperfect fit to trick your immune system through a process called antibody-dependent enhancement^[2].

This makes it easier for the virus to infect you and cause more serious illness. Individuals who are infected for the second time are at greater risk of severe dengue^[3]. People who have had a previous dengue infection are at increased risk of developing severe dengue if they have a second infection^[16].

How Dengue is Diagnosed

Diagnosing dengue fever can be difficult because its signs and symptoms can be easily confused with those of other diseases, such as chikungunya, Zika virus, malaria, and typhoid fever^[10].

Your doctor will likely ask about your medical and travel history. Be sure to describe international trips in detail, including the countries you visited and the dates, as well as any contact you may have had with mosquitoes^[10]. If you develop a fever or have symptoms of dengue, tell your doctor about any recent travel^[4].

Your doctor may also draw a sample of blood to be tested in a lab for evidence of infection with one of the dengue viruses^[10]. Blood tests are available to confirm the diagnosis, including detecting viral RNA or antibodies to the virus^[5]. These tests include the NS1 antigen test and PCR for early detection and IgM and IgG antibody tests for later stages^[21].

Treatment and Recovery

No specific treatment for dengue fever exists^[10]. There is no specific medicine to treat dengue^[4]. Dengue is treated through pain management, as there is no specific treatment currently^[3].

While recovering from dengue fever, treatment focuses on supportive care^[1]:

• Rest as much as possible^[13]
• Drink plenty of fluids to stay hydrated. Drink water or drinks with added electrolytes^[13]
• Take acetaminophen (also known as paracetamol) to control fever and relieve pain^[13]

If you have dengue fever, you should avoid other pain relievers, including aspirin, ibuprofen, and naproxen sodium. These pain relievers can increase the risk of dengue fever bleeding complications^[10]. Do not take aspirin or ibuprofen^[13]!

Call your doctor right away if you have any signs of dehydration, such as decreased urination, few or no tears, dry mouth or lips, lethargy or confusion, or cold or clammy extremities^[10].

For mild symptoms, care for a sick infant, child, or family member at home^[13]. Most people recover within a week or so^[1]. Dengue fever usually lasts between 2 to 7 days^[6]. After recovery, people who have had dengue may experience fatigue for several weeks^[3].

Severe Dengue Treatment

If you have severe dengue fever, you may need^[10]:

• Supportive care in a hospital
• Intravenous (IV) fluid and electrolyte replacement
• Blood pressure monitoring
• Transfusion to replace blood loss

Symptoms of dengue can become severe within a few hours. Severe dengue is a medical emergency^[13]. Early detection and access to proper medical care greatly lower fatality rates of severe dengue^[3].

Prevention

In areas where dengue fever is common, the best ways to prevent infection are to avoid being bitten by mosquitoes and to take steps to reduce the mosquito population^[1]. The best way to prevent dengue is to avoid mosquito bites^[4].

You can lower your risk of dengue by avoiding mosquito bites, especially during the day^[3]. Some tips to avoid mosquito bites include^[8]:

• Use insect repellent
• Empty standing water
• Wear protective clothing
• Limit time outside at dusk and dawn

Dengue prevention and control must be intersectoral and involve the family and the community^[7]. Prevention and control of dengue rely on vector control^[3].

If you have dengue, prevent mosquito bites. During the first week of illness, dengue can be found in the blood. The virus can be passed from an infected person to a mosquito through mosquito bites^[13].

Dengue Vaccine

In the United States, there is a dengue vaccine recommended for use in children 9 through 16 with laboratory confirmation of a previous dengue infection, living in areas where dengue is common^[4]. The vaccine is not approved for use in U.S. travelers who are visiting but not living in an area where dengue is common^[4].

While there is an FDA-licensed vaccine in the US to protect against dengue in special circumstances, the manufacturer is discontinuing production due to lack of demand. However, doses will be available in Puerto Rico until 2026^[8].

Researchers are working on dengue fever vaccines^[1].