Signs and symptoms of dengue fever vary, depending on the form and severity of the disease.

Dengue fever
With the mild form of the disease, you may experience some or all of these signs and symptoms:

• High fever, up to 105 F (40.6 C)
• A rash over most of your body, which may subside after a couple of days and then reappear
• Severe headache, backache or both
• Pain behind your eyes
• Severe joint and muscle pain
• Nausea and vomiting

Sign and symptoms usually begin about four to seven days after being bitten by a mosquito carrying a dengue virus. Mild dengue fever rarely causes death, and your symptoms will usually subside within a week after starting.

Dengue hemorrhagic fever
More-severe forms of the disease usually begin the same way as the mild form (dengue fever) then become worse after several days.

Dengue hemorrhagic fever — a more severe form of the disease than initial dengue fever — can cause signs and symptoms of dengue fever plus:

• Significant damage to your blood and lymph vessels
• A decrease in the number of blood cells that help your blood clot (platelets)
• Bleeding from the nose and mouth
• Bleeding under the skin, which gives the appearance of bruising
• Death

Dengue shock syndrome — Dengue shock syndrome — the most severe form of the disease — may cause signs and symptoms of mild dengue fever plus:

• Severe abdominal pain
• Frequent vomiting
• Disorientation
• Fluid (plasma) leakage from blood vessels
• Heavy bleeding
• A sudden drop in blood pressure (shock)
• Death

Severe signs and symptoms may appear after your fever has improved. In a small number of cases, people with a severe form of the disease die of it. Modern supportive hospital care decreases this risk.

When to see a doctor
If you have any signs or symptoms of dengue fever, see your doctor. If you've recently traveled to a region in which the disease is known to occur, be sure to inform your doctor.

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Dengue fever is caused by any one of four dengue viruses spread by the Aedes aegypti mosquito. These mosquitoes thrive in and near human habitations, where they breed in even the cleanest water.

Mosquitoes transmit the virus back and forth between humans. When a mosquito bites a person infected with a dengue virus, the virus enters the mosquito's bloodstream. It then circulates before settling in the salivary glands. When the infected mosquito then bites another person, the virus enters that person's bloodstream, where it may cause the serious illness.

You can become infected with dengue fever more than once. This happens when you're exposed to a different one of the four dengue viruses from the one to which you were previously exposed. Infection a second time is typically what causes the more severe form of the disease — dengue hemorrhagic fever.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

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 around the world — especially in high-risk areas, such as tropical Asia, Central and South America, and the Caribbean — increases your risk of exposure to the virus that causes dengue fever. Dengue virus transmission occurs year-round, although the risk is highest during a recognized dengue fever outbreak.
• Prior infection with a dengue fever virus. Previous infection with a dengue fever virus increases your risk of a more severe form of the disease. This is especially true for children. If you've had dengue fever before, you can get it again if you become infected with another one of the four dengue-causing viruses. Having antibodies to a virus in your blood from a previous infection usually helps protect you. But in the case of dengue fever, it actually increases your risk of severe disease — dengue hemorrhagic fever — if you're infected again.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Most people with dengue fever recover within five to 14 days. Some, particularly adults, may feel listless, tired and even depressed for several weeks to months after being infected.

If severe, dengue fever can lead to dengue hemorrhagic fever and dengue shock syndrome, which can cause heavy bleeding, shock and — in a small number of those with these conditions — death. Those who survive may experience liver, blood vessel and brain damage, as well as seizures.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

You'll likely start by seeing your family doctor or primary care provider. But in some cases, when you call to set up an appointment, you might be referred instead to a doctor who specializes in infectious diseases. If your symptoms are severe, you might be instructed to seek urgent care.

Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared for your appointment. Here's some information to help you get ready, and what to expect from your doctor.

What you can do

• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information. List your international travel history, with dates and countries visited and medications taken while traveling. Bring a record of your immunizations, including pre-travel immunizations.
• Make a list of all medications, as well as any vitamins or supplements, that you're taking.
• Take a family member or friend along, if possible. Sometimes it can be difficult to soak up all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor. Your time with your doctor is limited, so preparing a list of questions will help you make the most of your time together. List your questions from most important to least important in case time runs out.

For dengue fever, some basic questions to ask your doctor include:

• What is likely causing my symptoms or condition?
• What kinds of tests do I need?
• What's the best course of action?
• How long will it be before I'm feeling better?
• Are there any long-term effects of this illness?
• Do you have any brochures or other printed material that I can take home with me? What Web sites do you recommend?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Be prepared to answer questions from your doctor, such as:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• Does anything seem to make your symptoms better or worse?
• Where have you traveled in the past 12 months?
• Were you bitten by mosquitoes while traveling?
• Have you been in contact recently with anyone who was ill?

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Diagnosing dengue fever can be difficult. That's because its signs and symptoms can be easily confused with those of other diseases, such as malaria, leptospirosis and typhoid fever. To diagnose dengue fever, your doctor will:

• Evaluate your signs and symptoms
• Review your medical and travel history
• Test your blood for evidence of a dengue virus

Medical history
Your doctor will likely ask about your medical and travel history and any exposure to mosquitoes. Be sure to describe international trips in detail, including the countries you visited and the dates, as well as any contact you may have had with mosquitoes.

Blood tests
Laboratory tests, usually using a sample of your blood, are needed to confirm a diagnosis of dengue fever. If you have dengue fever, your blood may reveal the virus itself. If not, blood tests known as hemagglutination inhibition (HI) assay, enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase-polymerase chain reaction (RT-PCR) can detect antigens, antibodies or nucleic acids specific to the viruses. These tests may take several days.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

No specific treatment for dengue fever exists.

For a mild form of the disease, your doctor may recommend:

• Drinking plenty of fluids to avoid dehydration from vomiting and high fever.
• Taking acetaminophen (Tylenol, others) to alleviate pain and reduce fever. Don't take aspirin or other nonsteroidal anti-inflammatory drugs, such as ibuprofen (Advil, Motrin, others) and naproxen sodium (Aleve, others). These can increase the risk of bleeding complications.

For a more severe form of the disease, treatment consists of:

• Supportive care in a hospital
• Intravenous (IV) fluid and electrolyte replacement
• Blood pressure monitoring
• Transfusion to replace blood loss

If you have any form of dengue fever, you may also be kept away from mosquitoes, to avoid transmitting the disease to others.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

A dengue fever vaccine is in development but isn't generally available. If you're living or traveling in an area where dengue fever is known to be, the best way to avoid dengue fever is to avoid being bitten by mosquitoes that carry the disease.

To reduce your risk of mosquito bites, minimize your exposure to mosquitoes:

• Schedule outdoor activities for times when mosquitoes are less prevalent. Avoid being outdoors at dawn, dusk and early evening, when more mosquitoes are buzzing about.
• Wear long-sleeved shirts, long pants, socks and shoes when you go into mosquito-infested areas.
• Stay in air-conditioned or well-screened housing. Patch screens if necessary, especially where there will be nighttime exposure.
• Apply permethrin-containing mosquito repellent to your clothing, shoes, and camping gear and bed netting. You can also buy clothing made with permethrin already in it.
• Use repellent with a 10 to 30 percent concentration of DEET on your skin. Choose the concentration based on the hours of protection you need — a 10 percent concentration of DEET is effective for about two hours; higher concentrations last longer. However, chemical repellents can be toxic, so use only the amount needed for the time you'll be outdoors.

Don't use DEET on the hands of young children or on infants under 2 months of age. Instead, cover your infant's stroller or playpen with mosquito netting when outside. According to the Centers for Disease Control and Prevention, oil of lemon eucalyptus, a more natural product, offers the same protection as DEET when used in similar concentrations.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.