Dengue Fever: Causes, Symptoms, Diagnosis and Treatment

Dengue fever is a viral infection that can cause a wide range of symptoms, including life-threatening illness, milder flu-like illness, or sometimes no symptoms at all. About one in four people infected will get sick, according to the Centers for Disease Control and Prevention (CDC).

In recent decades, the number of new cases of dengue has increased dramatically. The World Health Organization (WHO) notes that changing land use patterns, increased international travel and trade, and the climate crisis have contributed to the spread of dengue

Dengue Mosquito

Dengue virus (DENV) is spread by bites from Aedes mosquitoes, the same genus of mosquito that spreads the Zika virus and the virus that causes yellow fever.

There are four subtypes (called “serotypes”) of dengue. Each serotype can infect you only once, but infection with one serotype doesn’t provide immunity against the other serotypes, so you can still become infected by the other serotypes of dengue.

With your first dengue infection, you may have few or no symptoms. Unfortunately, the risk for severe dengue increases with each infection.

Signs and Symptoms of Dengue Fever

Symptoms of dengue fever typically develop between 4 and 10 days after a bite from an infected female Aedes mosquito.right up arrow
Classic symptoms include:

• Fever
• Headache and pain behind the eyes
• Severe muscle and joint pain (the source of dengue's nickname, "breakbone fever")right up arrow
• Extreme fatigue
• Rash
• Bloody stools
• Nausea and vomiting

These symptoms usually last for two to seven days, at which point the fever breaks (referred to as “defervescence”).
After defervescence, people either start to get better or they get much worse, developing severe dengue.

Approximately 1 in 20 people with DENV illness go on to develop severe dengue.right up arrow
According to the CDC, the following symptoms are warning signs that may signal the development of severe dengue, often called dengue hemorrhagic fever (DHF):

• Abdominal pain or tenderness
• Persistent vomiting
• Lethargy or restlessness
• Mucosal bleeding, such as bleeding gums or nosebleeds
• Liver enlargement
• Fluid retention

Causes and Risk Factors of Dengue Fever

The virus subtypes that cause dengue fever are spread by female mosquitoes of the species Aedes aegypti, and less commonly by Aedes albopictus.

According to the World Health Organization, Aedes mosquitoes are usually found in urban and suburban areas, as they like to breed in man-made containers such as tires, flowerpots, and household water containers.right up arrow They bite during the day, especially near dawn and dusk.

How Is Dengue Fever Diagnosed?

Dengue diagnosis is ideally made with a laboratory blood test, but diagnosis is also often made on the basis of symptoms and on the prevalence of the illness in the geographic area where the person lives or has traveled.

CDC recommendations for diagnostic testing state that the preferred blood tests are either a molecular test known as a nucleic acid amplification test (NAAT), or a test specific to dengue called an NS-1 test, both of which are useful in the first week of illness.right up arrow
Plaque reduction neutralization tests (PRNT) are specific antibody tests that are also sometimes used to make the diagnosis.right up arrow Other antibody tests of the blood (referred to as “serology” or “IgM” tests) are also possibilities after the first week of infection, but they may not be as accurate as the NAAT, NS1, or PRNT tests.

If a person is showing neurological signs of infection, such as meningitis or encephalopathy, a test of the cerebrospinal fluid (CSF) may also be performed, in addition to testing the person’s blood.

Prognosis of Dengue Fever

With proper medical care, the mortality rate from dengue is less than 1 percent. Without proper management, the fatality rate can be as high as 20 percent in patients with severe dengue, according to the WHO.right up arrow
Treatment and Medication Options for Dengue Fever
As with most viruses, treatment options for dengue will only manage its symptoms.

Pain relievers and fever reducers that don't make bleeding worse may be taken, such as Tylenol (acetaminophen).

To stay hydrated, drink plenty of water or drinks with added electrolytes.right up arrow

Severe dengue may require intravenous (IV) fluids and electrolyte replacement, blood pressure monitoring, and even a blood transfusion, if there's significant blood loss.

Prevention of Dengue Fever

Dengue does not spread directly from person to person, but a person sick with dengue can infect mosquitoes in the area, and those mosquitoes will become contagious to other humans within 8 to 12 days.

7 Natural Ways to Prevent Mosquito Bites

Preventing Mosquito Bites

The primary way to prevent infection with dengue is to prevent mosquito bites in geographic regions where dengue is present. Light-colored clothing and insect repellent can help, as can window screens and mosquito netting.

Source Reduction at Mosquito Breeding Sites

Preventive measures are often geared at eliminating Aedes females' egg-laying sites, a method called "source reduction." Anything that contains standing water can be used by Aedes for laying eggs, from plant saucers to rainwater drums and potholes. Water containers should be kept covered. Unnecessary containers should be disposed of, and necessary water containers should be emptied and scrubbed weekly to remove mosquito eggs.

Infecting Mosquitoes With Competing Bacteria

A recent study has used a genus of bacteria called Wolbachia to infect mosquitoes and compete against the viruses that might infect humans, with promising results, according to the WHO.

Wolbachia bacteria are harmless to humans and also to mosquitoes, but the bacteria make it more difficult for mosquitoes to transmit dengue viruses (DENV) or other viruses that are similar to dengue. One research study showed a 77 percent reduction in dengue cases where Wolbachia-infected Aedes mosquitoes were released, translating into a fourfold reduction in illness from dengue.

Dengvaxia Vaccine

A vaccine called Dengvaxia received very limited approval from the U.S. Food and Drug Administration (FDA) in 2019.right up arrow
The FDA has approved the vaccine to be given to people who:

• Are age 9 to 16
• Live in areas where dengue is endemic; endemic areas under the FDA’s purview include the U.S. territories of American Samoa, Guam, Puerto Rico, and the U.S. Virgin Islands
• Have previously been infected with dengue, as shown by medical records or a blood test that shows immunity

Complications of Dengue Fever

About 1 in 20 people with dengue will develop severe dengue, according to the CDC.

Dengue hemorrhagic fever (DHF)

DHF is the most serious form of dengue infection. DHF is a clinical syndrome defined by four key features:

• Increased permeability of blood vessels, leading to plasma leakage into the surrounding tissues and lack of plasma (the liquid part of the blood) in the bloodstream. This can lead to shock, a condition in which there is inadequate blood flow to vital organs.
• Low blood platelet count
• Fever that lasts for two to seven days
• Tendency toward severe (hemorrhagic) bleeding

While bleeding (hemorrhage) is alarming, the most life-threatening concern of DHF is the leakage of plasma into tissues surrounding the blood vessels. When this happens, blood pressure drops and the body goes into shock. In shock, organ failure or death can occur due to inadequate blood flow and oxygen delivery to essential organs.

The term dengue shock syndrome (DSS) is used when an infected person has gone into shock.