Dengue Fever: Causes, Symptoms, Treatment, and Prevention

Dengue fever is a viral infection that is transmitted by mosquitoes and can cause severe complications and even death. It is one of the most common mosquito-borne diseases in the world, affecting millions of people every year. In this article, we will explain what dengue fever is, what are its symptoms and causes, how it is diagnosed and treated, and how it can be prevented.

What is Dengue Fever?

Dengue fever is a disease caused by any of the four types of dengue viruses (DENV-1, DENV-2, DENV-3, or DENV-4) that belong to the Flavivirus genus. These viruses are spread by the bite of infected female Aedes mosquitoes, which are mainly active during the day. The mosquitoes can also transmit other diseases, such as Zika, chikungunya, and yellow fever.

Dengue fever can range from mild to severe, depending on the type of virus and the person’s immune system. Mild dengue fever causes flu-like symptoms, such as fever, headache, muscle and joint pain, nausea, vomiting, rash, and swollen glands. Severe dengue fever, also known as dengue hemorrhagic fever or dengue shock syndrome, can cause serious bleeding, shock, organ failure, and death.

Dengue fever is endemic in more than 100 countries in tropical and subtropical regions of the world, especially in Southeast Asia, the Western Pacific islands, Latin America, and Africa. According to the World Health Organization (WHO), about 390 million dengue infections occur every year, of which 96 million result in illness. About 3.9 billion people are at risk of infection. Dengue fever is also a potential threat to travelers who visit endemic areas.

What are the Symptoms of Dengue Fever?

The symptoms of dengue fever usually appear 4 to 10 days after being bitten by an infected mosquito. The symptoms vary depending on the severity of the infection.

Mild dengue fever symptoms include:

• High fever (104 F or 40 C)
• Headache
• Pain behind the eyes
• Muscle, bone, or joint pain
• Nausea or vomiting
• Rash
• Swollen glands
• Fatigue

Most people recover from mild dengue fever within a week or so. However, some people may develop severe dengue fever, which can be life-threatening.

Severe Symptoms

Severe dengue fever symptoms include:

• Severe abdominal pain
• Persistent vomiting
• Bleeding from the gums, nose, or under the skin
• Blood in the urine, stool, or vomit
• Difficulty breathing
• Cold or clammy skin
• Restlessness or irritability
• Low blood pressure or shock

Severe dengue fever can lead to complications such as:

• Dehydration
• Low platelet count (thrombocytopenia)
• Blood vessel leakage (plasma leakage)
• Organ damage (liver, kidney, heart)
• Brain infection (encephalitis)
• Death

The warning signs of severe dengue fever usually occur after the fever subsides. Therefore, it is important to seek medical attention immediately if you notice any of these signs.

What are the Causes of Dengue Fever?

Dengue fever is caused by any of the four types of dengue viruses that infect humans. These viruses are transmitted by the bite of infected female Aedes mosquitoes. The mosquitoes become infected when they feed on the blood of a person who has dengue virus in their bloodstream. The virus then multiplies in the mosquito’s body and is released into its saliva. When the mosquito bites another person, it injects the virus into their skin.

The dengue virus can infect various cells in the human body, such as white blood cells (monocytes and macrophages), endothelial cells (lining blood vessels), liver cells (hepatocytes), and nerve cells (neurons). The virus triggers an immune response that causes inflammation and damage to these cells and tissues.

The severity of dengue fever depends on several factors, such as:

The type of dengue virus:

There are four types of dengue viruses (DENV-1 to DENV-4) that can cause different clinical manifestations. In general, DENV-2 and DENV-3 are more likely to cause severe disease than DENV-1 and DENV-4.

Previous exposure to dengue virus:

A person who has been infected by one type of dengue virus develops lifelong immunity to that type but only partial and temporary immunity to the other types. This means that a person can be infected by different types of dengue virus up to four times in their lifetime. A second or subsequent infection by a different type of dengue virus increases the risk of developing severe disease due to a phenomenon called antibody-dependent enhancement (ADE). ADE occurs when the antibodies from the previous infection bind to the new virus and facilitate its entry into the cells, leading to increased viral replication and immune activation.

The genetic factors of the host:

Some people may have genetic variations that affect their susceptibility or resistance to dengue virus infection. For example, some people may have genes that encode for receptors or enzymes that are involved in viral entry or replication. Some people may also have genes that regulate the immune response or the coagulation system that are associated with the severity of dengue fever.

The environmental factors:

The transmission and spread of dengue fever are influenced by environmental factors, such as temperature, rainfall, humidity, and urbanization. These factors affect the breeding and survival of the mosquitoes, as well as their biting behavior and vector competence. For example, higher temperatures and rainfall increase the mosquito population and activity, while lower humidity reduces their lifespan. Urbanization creates favorable conditions for the mosquitoes to breed in artificial containers, such as tires, cans, pots, and barrels.

How is Dengue Fever Diagnosed?

Dengue fever is diagnosed based on the clinical symptoms, the medical history, and the laboratory tests. The diagnosis can be challenging because the symptoms of dengue fever are similar to those of other diseases, such as malaria, typhoid fever, leptospirosis, and COVID-19.

The laboratory tests for dengue fever include:

Virus isolation:

This test involves culturing the blood sample in a cell culture or a mosquito cell line to detect the presence of the virus. This test is very specific but requires specialized equipment and expertise. It is also time-consuming and not widely available.

Nucleic acid amplification:

This test involves using polymerase chain reaction (PCR) or loop-mediated isothermal amplification (LAMP) to amplify and detect the viral RNA in the blood sample. This test is very sensitive and specific but requires expensive equipment and trained personnel. It is also prone to contamination and false positives.

Antigen detection:

This test involves using enzyme-linked immunosorbent assay (ELISA) or rapid diagnostic tests (RDTs) to detect viral antigens, such as NS1 protein, in the blood sample. This test is relatively simple and fast but less sensitive and specific than nucleic acid amplification. It may also cross-react with other flaviviruses, such as Zika or yellow fever.

Antibody detection:

This test involves using ELISA or RDTs to detect the antibodies (IgM and IgG) produced by the immune system against the virus in the blood sample. This test is useful for confirming a past or recent infection but not for diagnosing an acute infection. It may also cross-react with other flaviviruses or produce false negatives due to ADE.

The laboratory tests for dengue fever should be interpreted in conjunction with the clinical symptoms and epidemiological data. The results should be confirmed by a second test using a different method or a different sample.

How is Dengue Fever Treated?

There is no specific antiviral treatment for dengue fever. The treatment is mainly supportive and aims to relieve the symptoms and prevent complications.

The treatment for mild dengue fever includes:

• Resting and drinking plenty of fluids to prevent dehydration
• Taking paracetamol (acetaminophen) to reduce fever and pain
• Avoiding aspirin, ibuprofen, or other nonsteroidal anti-inflammatory drugs (NSAIDs) that can increase bleeding risk
• Monitoring for any signs of severe dengue fever

The treatment for severe dengue fever includes:

• Hospitalization and intensive care
• Intravenous fluids and electrolytes to maintain blood pressure and hydration
• Blood transfusion or platelet transfusion to correct bleeding or thrombocytopenia
• Oxygen therapy or mechanical ventilation to support breathing
• Antibiotics to treat any secondary bacterial infections
• Painkillers and antipyretics to reduce fever and pain

The recovery from dengue fever depends on the severity of the infection and the presence of any complications. Most people recover fully from mild dengue fever within a week or two. However, some people may experience prolonged fatigue, weakness, depression, or memory loss after recovering from severe dengue fever.

How can Dengue Fever be Prevented?

There is no vaccine available for dengue fever yet. The best way to prevent dengue fever is to avoid being bitten by mosquitoes and to reduce their breeding sites.

The following measures can help prevent mosquito bites:

• Wearing long-sleeved shirts, long pants, socks, shoes, and hats when outdoors
• Applying insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus on exposed skin
• Using mosquito nets treated with insecticides over beds or windows
• Installing screens or air conditioners on doors or windows