Everything you need to know about Dengue fever
Symptoms range from mild to severe. Severe symptoms include dengue shock syndrome (DSS) and dengue hemorrhagic fever (DHF). These usually require hospitalization.
There are currently no vaccines. The best method of prevention is to avoid mosquito bites. Treatment is possible if diagnosis occurs before the patient develops DSS or DHF.
The Centers for Disease Control and Prevention (CDC) estimate that 400 million people are infected each year.
Dengue fever is rare in the United States (U.S.), but around 100 cases are reported each year, mostly among people traveling from outside the country. Outbreaks have occurred in Texas, Florida, and Hawaii.
Here are some key points about dengue fever. More detail is in the main article.
- Dengue is transmitted by the mosquitoes Aedes aegypti and Aedes albopictus, which are found throughout the world.
- Around 2.5 billion people, or 40 percent of the world's population, live in areas where there is a risk of dengue transmission.
- Dengue is endemic in at least 100 countries in Asia, the Pacific, the Americas, Africa, and the Caribbean.
- Symptoms usually begin 4 to 7 days after the mosquito bite and typically last 3 to 10 days.
- Effective treatment is possible if a clinical diagnosis is made early.
Signs and symptoms
Mosquitoes spread dengue fever.
Symptoms vary depending on the severity of the disease.
Mild dengue fever
Symptoms can appear up to 7 days after being bitten by the mosquito that carries the virus.
- aching muscles and joints
- body rash that can disappear and then reappear
- high fever
- intense headache
- pain behind the eyes
- vomiting and feeling nauseous
Symptoms usually disappear after a week, and mild dengue rarely involves serious or fatal complications.
Dengue hemorrhagic fever
At first, symptoms of DHF may be mild, but they gradually worsen within a few days. As well as mild dengue symptoms, there may be signs of internal bleeding.
A person with Dengue hemorrhagic fever may experience:
- bleeding from the mouth, gums, or nose
- clammy skin
- damage to lymph and blood vessels
- internal bleeding, which can lead to black vomit and feces, or stools
- a lower number of platelets in the blood
- sensitive stomach
- small blood spots under the skin
- weak pulse
Without prompt treatment, DHF can be fatal.
Dengue shock syndrome
DSS is a severe form of dengue. It can be fatal.
Apart from symptoms of mild dengue fever, the person may experience:
- intense stomach pain
- sudden hypotension, or a fast drop in blood pressure
- heavy bleeding
- regular vomiting
- blood vessels leaking fluid
Without treatment, this can result in death.
Early dengue fever rash
Image credit: Ranjan Premaratna, (2014).
Dengue fever recovery rash
Image credit: Ranjan Premaratna, (2012).
Aedes aegypti mosquito
Image credit: CDC/James Gathany, (2005).
Dengue is a virus, so there is no specific treatment or cure. However, intervention can help, depending on how severe the disease is.
For milder forms, treatment includes:
Preventing dehydration: A high fever and vomiting can dehydrate the body. The person should drink clean water, ideally bottled rather than tap water. Rehydration salts can also help replace fluids and minerals.
Painkillers, such as Tylenol or paracetamol: These can help lower fever and ease pain.
Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin or ibuprofen, are not advised, as they can increase the risk of internal bleeding.
More severe forms of dengue fever may need:
- intravenous (IV) fluid supplementation, or drip, if the person cannot take fluids by mouth
- blood transfusion, for patients with severe dehydration
Hospitalization will allow the individual to be properly monitored, in case symptoms get worse.
There are four dengue viruses (DENV) that cause dengue fever. They are all spread by a species of mosquito known as Aedes aegypti, and more rarely by the Aedes albopictus mosquito.
The viruses jumped from monkeys to humans between 100 and 800 years ago, according to the CDC, but dengue remained a minor problem until the middle of the twentieth century.
Aedes aegypti originated in Africa, but nowadays it is found in tropical areas around the world, especially in and around areas of human population.
The virus is transmitted from an infected mosquito to a human. A mosquito bites a person who is infected with the dengue virus, and the virus is passed on when the mosquito bites someone else.
It it possible to have dengue fever more than once. A second infection carries a higher risk of developing a harsher form.
Dengue fever is most common in subtropical and tropical areas, such as Central and South America, parts of Africa, parts of Asia, the Caribbean, and the Pacific.
Most cases of dengue among U.S. citizens occur in Puerto Rico, the U.S. Virgin Islands, Samoa, and Guam, where the virus is endemic.
High-risk regions are:
- Central and South America
- the Caribbean
- tropical Asia, including Bangladesh, Indonesia, and parts of China
- Northern Australia
The signs and symptoms of dengue fever are similar to some other diseases, such as typhoid fever and malaria. This can sometimes delay an accurate diagnosis.
The doctor will assess the symptoms and the person's medical and travel history, and they may order some blood tests to confirm the diagnosis.
No vaccine can protect against dengue fever. Only avoiding mosquito bites can prevent it.
Anyone who lives in or travels to an at-risk area can use a number of ways to avoid being bitten.
If you are spending time in a tropical region, use mosquito nets that are treated with insecticide.
Clothing: Reduce the amount of skin exposed by wearing long pants, long-sleeved shirts, and socks, tucking pant legs into shoes or socks, and wearing a hat.
Mosquito repellents: Use a repellent with at least 10 percent concentration of diethyltoluamide (DEET), or a higher concentration for longer lengths of exposure. Avoid using DEET on young children.
Mosquito traps and nets: Nets treated with insecticide are more effective, otherwise the mosquito can bite through the net if the person is standing next to it. The insecticide will kill mosquitoes and other insects, and it will repel insects from entering the room.
Door and window screens: Structural barriers, such as screens or netting, can keep mosquitos out.
Avoid scents: Heavily scented soaps and perfumes may attract mosquitos.
Camping gear: Treat clothes, shoes, and camping gear with permethrin, or purchase clothes that have been pretreated.
Timing: Try to avoid being outside at dawn, dusk, and early evening.
Stagnant water: The Aedes mosquito breeds in clean, stagnant water. Checking for and removing stagnant water can help reduce the risk.
To reduce the risk of mosquitoes breeding in stagnant water:
- turn buckets and watering cans over and store them under shelter so that water cannot accumulate
- remove excess water from plant pot plates
- scrub containers to remove mosquito eggs
- loosen soil from potted plants, to prevent puddles forming on the surface
- make sure scupper drains are not blocked and do not place potted plants and other objects over them
- use non-perforated gully traps, install anti-mosquito valves, and cover any traps that are rarely used
- do not place receptacles under an air-conditioning unit
- change the water in flower vases every second day and scrub and rinse the inside of the vase
- prevent leaves from blocking anything that may result in the accumulation of puddles or stagnant water
When camping or picnicking, choose an area that is away from still water.