Also called: Dengue Virus
Vikram Tarugu, M.D., AGA, ACG
Dengue virus infection occurs when people are bitten by a mosquito carrying any one of four closely related viruses. In most cases, the disease causes a flu-like illness that passes on its own within a couple of weeks. However, more severe types of dengue virus infection can be fatal.
A mosquito known as Aedes aegypti is the most common carrier of dengue viruses. Mosquitoes often become infected after biting a person who has dengue. About a week later, the mosquito becomes contagious and passes the virus to other people after biting them.
Dengue infection usually occurs in tropical urban areas of the world, where Aedes aegypti mosquitoes live. However, the virus also can appear in other regions if people visit or return to those places after being infected in a tropical part of the world. Dengue infection can take several forms of varying severity. Symptoms of the first, dengue fever, typically include a sudden high fever and severe joint and muscle pain. Symptoms of the more severe and potentially life-threatening condition called dengue hemorrhagic fever include tendency to bruise easily, bleeding from the nose or gums, and internal bleeding.
Two blood tests performed two to three weeks apart can help diagnose dengue infection. These tests reveal the presence of antibodies created by the immune system in response to dengue infection.
Treatment of dengue virus infection varies depending on the nature of the illness. There is no standard treatment for dengue virus aside from rest and drinking plenty of fluids until the virus passes from the system, usually in about two weeks. Treatment of the more serious dengue hemorrhagic fever usually requires hospitalization and fluid and electrolyte replacement therapy. There is no vaccine against dengue, although several are being developed. For now, the best way to prevent dengue virus infection is to avoid being bitten by mosquitoes.
About dengue virus infection
Dengue virus infection occurs when patients are bitten by a mosquito carrying any one of four closely related flaviviruses. There are about 50 million cases of dengue infection worldwide each year, with more than 600,000 diagnosed in the Americas (e.g., Mexico, Central America), according to the World Health Organization.
A mosquito known as Aedes aegypti is the most common carrier of dengue viruses, although other mosquito species also can cause infections. For example, a 2001 outbreak of dengue in Hawaii was caused by a mosquito called Aedes albopictus. Mosquitoes often become infected after biting a person who has dengue. About a week later, the mosquito becomes contagious and passes the virus to other people after biting them. Dengue cannot be passed from person to person.
Most cases of dengue infection are dengue fever, which may have alarming symptoms and pain, but generally resolves on its own. A more severe dengue infection is called dengue hemorrhagic fever. People can be infected with all four types of dengue virus. After a person is infected with a form of the virus, reinfection with the same virus cannot occur. However, a person can be infected with another strain. Most cases of dengue hemorrhagic fever appear to develop only or mostly in people who have developed immunity to one strain of dengue and then are infected by a separate strain. This type of dengue infection can be fatal if left untreated.
Dengue infection usually occurs in tropical urban areas of the world, where Aedes aegypti mosquitoes live. This includes areas such as Africa, Australia, the Caribbean, Central and South America, China, India, the Middle East, Southeast Asia, and the South and Central Pacific. However, the virus also can appear in other regions if people visit or return to those places after being infected in a tropical part of the world. Most cases of dengue in the United States are due to travelers returning from tropical urban areas.
Many scientists also believe that increasing temperatures worldwide could cause the range of the carrier mosquitoes – and thus the virus itself – to spread into more temperate areas. In the United States, between 100 and 200 cases of dengue virus infection are reported annually, according to the U.S. Centers for Disease Control and Prevention (CDC). However, it is believed that other cases may go unreported because health care providers do not recognize the disease.
Risk factors/causes of dengue virus infection
Dengue infection occurs when patients are bitten by a mosquito carrying any one of four closely related flaviviruses. These flaviviruses are known as DEN-1, DEN-2, DEN-3 and DEN-4. A mosquito known as Aedes aegypti is the most common carrier of dengue viruses, although other mosquito species also can cause infections.
Dengue viruses appear in tropical urban areas throughout the world, although is less common in the mainland United States. The DEN-3 strain was absent from Central America for 20 years but was reintroduced there in 1994. The long period of absence has left the local population with a low level of immunity to the virus, and it is expected to spread rapidly.
The risk factors for dengue infection relate to the areas known to be habitats of the mosquitoes that serve as vectors. People who live in or visit urban areas in tropical zones are at increased risk for infection. Infection with one type of DEN virus provides immunity from future infection from that type, but not from infection with the other three types.
Children and the elderly in these urban tropical areas are also at increased risk of developing dengue infections.
Signs and symptoms of dengue virus infection
Symptoms of dengue fever typically appear five to six days after a person has been bitten by an infected mosquito. Typically, a sudden high fever develops of between 104 and 105 degrees Fahrenheit (40 and 40.5 degrees Celsius). Other symptoms include:
- Severe headache
- Enlarged lymph nodes
- Eye pain
Severe joint and muscle pain often accompanies dengue virus infection. For this reason, the condition is sometimes called “breakbone fever.” A flat, red rash often develops early in the disease. Later, a second measles-like rash may appear. Patients often report increased skin sensitivity that makes them feel very uncomfortable. The severity of dengue symptoms is likely to be reduced in young children when compared to older children and adults.
Symptoms of the more severe dengue hemorrhagic fever include all the symptoms of standard dengue infection, but may also include other symptoms, including tendency to bruise easily, bleeding from the nose or gums, and internal bleeding. In this condition, the smallest blood vessels in the body (capillaries) may become leaky, allowing fluid to escape and leading to failure of the circulatory system. This is sometimes known as dengue shock syndrome and it can result in shock and death if not corrected.
Diagnosis/treatment of dengue virus infection
To diagnose dengue virus infection, a physician will review a medical history and perform a physical examination. Two blood tests performed two to three weeks apart can help diagnose dengue fever. These tests reveal the presence of antibodies created by the immune system in response to dengue infection. Blood testing also may reveal elevated levels of white blood cells, increase in hematocrit and decreased platelets.
Treatment of dengue virus infection varies depending on the nature of the illness. There is no standard treatment for dengue virus aside from rest and drinking plenty of fluids until the virus passes from the system in about two weeks. Patients should avoid using aspirin, but may gain pain relief from using other pain-relieving (analgesic) and fever-reducing medications. However, no patient should take any medication without first consulting a physician.
Treatment of dengue hemorrhagic fever usually requires hospitalization because this form of infection can be fatal if left untreated. In most cases, treatment involves fluid and electrolyte replacement therapy. When properly treated, this severe infection has a mortality rate of less than 1 percent. Without treatment, up to 20 percent of people infected with severe dengue virus infection may die, often within 24 hours after shock sets in. Some people who recover from dengue infection continue to feel tired or depressed for several weeks or months afterward.
Prevention methods for dengue virus infection
Dengue virus infection can usually be prevented by avoiding travel to areas where the disease is endemic. There is no vaccine against dengue, although several are being developed. For now, the best way to prevent dengue virus infection is to avoid being bitten by mosquitoes. People are urged to use mosquito repellents that have an active ingredient registered with the Environmental Protection Agency (EPA), such as N,N-diethyl-meta-toluamide (DEET).
Products with between 10 and 30 percent DEET are often advised. Insect repellent with a 10 percent concentration of DEET is effective for about two hours. Wearing repellent is especially important at dusk and dawn, when mosquitoes are the most active.
Repellent should not be used on skin covered by clothing. In addition, products should not be sprayed directly onto the face. Instead, the product should be sprayed on to the hands and then applied to the face (avoiding eyes and mouth). Repellent should not be sprayed into areas of the skin that are irritated or cut. People are urged to stop using repellent if they develop a rash or skin reaction.
Products containing 10 percent or less of DEET are safest for children aged 2 to 12 years. Repellent should not be applied to hands of children or used on infants under 2 months of age. Instead, the strollers and playpens of infants can be covered with mosquito netting.
Wearing long sleeves and pants also helps deprive mosquitoes of exposed skin on which to feed. However, mosquitoes can bite through thin clothing. Keeping well-maintained screens on windows and doors can help prevent mosquitoes from getting indoors.
Clothing, shoes, bed nets, camping gear and other products that contain the ingredient permethrin also can help ward off mosquitoes. Permethrin is a highly effective insecticide and repellent that continues to ward of mosquitoes, ticks and other arthropods even after repeated washings. People can also reduce mosquito breeding grounds by eliminating standing water by dumping it from buckets, barrels, flower pots and other containers. Water should be changed in bird baths and pet dishes at least weekly, and holes should be drilled in tire swings to allow water to drain out. Keeping children’s wading pools empty of water and resting on their sides also can eliminate potential breeding areas. Clogged gutters should be cleaned to prevent water from pooling.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to dengue virus infection:
- How can I tell if I have dengue virus infection?
- How do I know if my symptoms are serious enough to require medical treatment?
- How will you diagnose my dengue virus infection?
- What are my treatment options?
- What are the side effects of these treatments?
- What changes in my condition should I report to you?
- Is there anything I can do to prevent myself from getting dengue virus infection?
- Are there any steps I can take to help reduce my child’s risk of dengue virus infection?
- Where can I find products such as repellent with DEET or clothing treated with permethrin?
- What steps can I take to reduce the mosquito population around my house?