Dengue fever
Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. This may include a high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash.
Recovery generally takes two to seven days. In a small proportion of cases, the disease develops into severe dengue, also known as dengue hemorrhagic fever, resulting in bleeding, low levels of blood platelets and blood plasma leakage, or into dengue shock syndrome, where dangerously low blood pressure occurs.
Dengue is spread by several species of female mosquitoes of the Aedes type, principally A. aegypti. The virus has five types; infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with a different type increases the risk of severe complications. A number of tests are available to confirm the diagnosis including detecting antibodies to the virus or its RNA.
Dengue fever Signs and symptoms
Symptoms can appear up to 7 days after being bitten by the mosquito that carries the virus.
They include:
- 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
- Disorientation
- Sudden hypotension, or a fast drop in blood pressure
- Heavy bleeding
- Regular vomiting
- Blood vessels leaking fluid
Without treatment, this can result in death.
Dengue fever Causes
Dengue fever is caused by any one of four types of dengue viruses spread by mosquitoes that thrive in and near human lodgings. When a mosquito bites a person infected with a dengue virus, the virus enters the mosquito. When the infected mosquito then bites another person, the virus enters that person’s bloodstream.
After you’ve recovered from dengue fever, you have immunity to the type of virus that infected you — but not to the other three dengue fever virus types. The risk of developing severe dengue fever, also known as dengue hemorrhagic fever, actually increases if you’re infected a second, third or fourth time.
Dengue fever Risk factors
Factors that put you at greater risk of developing dengue fever or a more severe form of the disease include:
- Living or traveling in tropical areas. Being in tropical and subtropical areas increases your risk of exposure to the virus that causes dengue fever. Especially high-risk areas are Southeast Asia, the western Pacific islands, Latin America and the Caribbean.
- Prior infection with a dengue fever virus. Previous infection with a dengue fever virus increases your risk of having severe symptoms if you’re infected again.
Dengue fever Complications
If severe, dengue fever can damage the lungs, liver or heart. Blood pressure can drop to dangerous levels, causing shock and, in some cases, death.
Dengue fever Prevention
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.
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.
Dengue fever Treatment
Dengue is a virus, so there is no specific treatment or cure. However, an 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 the 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.
Rehydration salts, Tylenol, and paracetamol are available for purchase online.
Frequently asked questions about dengue fever
What is dengue fever?
Dengue fever is a viral illness spread to people primarily by Aedes mosquitoes the same mosquitoes that spread Zika and chikungunya). There are four closely related dengue viruses (DENV 1, DENV 2, DENV 3, and DENV 4). These viruses are spread to humans by the bite of an infected mosquito.
The disease occurs mainly in tropical Asia, Africa, the Caribbean, and the South Pacific. It is most common during the rainy season in areas infested with infected mosquitoes. Sometimes, persons arriving from other countries may enter the United States with dengue fever and infect local mosquitoes, as happened in Hawaii in 2001 and 2011. The current 2015 Hawaii Island outbreak involves the DENV serotype.
How do you get it?
The dengue virus is spread through the bite of infected Aedes mosquitoes, which are found throughout Hawaii. A mosquito can become infected if it feeds on someone who is already infected with the virus. This is why it is so important to stay away from mosquitoes when you are infected.
When an infected mosquito bites a new person, that mosquito can transmit the dengue virus to that new person. Dengue CANNOT be spread directly from person to person. It is estimated that there are over 100 million cases of dengue worldwide each year.
How are dengue and dengue hemorrhagic fever (DHF) spread?
Dengue is transmitted to people by the bite of an Aedes mosquito that is infected with a dengue virus. The mosquito becomes infected with dengue virus when it bites a person who has dengue or DHF and after about a week can transmit the virus while biting a healthy person. Dengue cannot be spread directly from person to person.
What are the symptoms of the disease?
The principal symptoms of dengue are high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain, and rash. Generally, younger children are more affected than older children and adults.
Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms that could occur with many other illnesses (e.g., nausea, vomiting, abdominal pain, and headache). This stage is followed by hemorrhagic manifestations, a tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding.
The smallest blood vessels (capillaries) become excessively permeable (“leaky”), allowing the fluid component to escape from the blood vessels. This may lead to failure of the circulatory system and shock, followed by death, if circulatory failure is not corrected.
What is the treatment for dengue?
There is no specific medication for the treatment of dengue infection. Persons who think they have dengue should use analgesics (pain relievers) with paracetamol and avoid those containing aspirin. They should also rest, drink plenty of fluids, and consult a physician
Is there an effective treatment for dengue hemorrhagic fever (DHF)?
As with dengue, there is no specific medication for DHF. It can, however, be effectively treated by fluid replacement therapy if an early clinical diagnosis is made. Hospitalization is frequently required in order to adequately manage DHF.
Where can outbreaks of dengue occur?
Outbreaks of dengue occur primarily in areas where Aedes aegypti (sometimes also Aedes albopictus) mosquitoes are found in large numbers. This includes urban areas as well as rural areas. Dengue viruses may be introduced into areas by migratory workers who become infected while visiting other endemic areas, where dengue commonly exists.
What can be done to reduce the risk of acquiring dengue?
There is no vaccine for preventing dengue. The best preventive measure for residents living in areas infested with Aedes aegypti is to eliminate the places where the mosquito lays her eggs, primarily artificial containers that hold