Viral hemorrhagic (hem-uh-RAJ-ik) fevers are infectious diseases that interfere with the blood's ability to clot. These diseases can also damage the walls of tiny blood vessels, making them leaky. The internal bleeding that results can range from relatively minor to life-threatening.
Some viral hemorrhagic fevers include:
These diseases most commonly occur in tropical areas of the world. When viral hemorrhagic fevers occur in the United States, they're usually found in people who've recently traveled internationally.
Viral hemorrhagic fevers are spread by contact with infected animals, people or insects. No current treatment can cure viral hemorrhagic fevers, and immunizations exist for only a few types. Until additional vaccines are developed, the best approach is prevention.
Signs and symptoms of viral hemorrhagic fevers vary by disease. In general, initial symptoms may include:
Severe cases of some types of viral hemorrhagic fevers may cause bleeding, but people rarely die of blood loss. Bleeding may occur:
Other signs and symptoms of severe infections can include:
The best time to see a doctor is before you travel to a developing country to ensure you've received any available vaccinations and pre-travel advice for staying healthy.
If you develop signs and symptoms once you return home, consult a doctor, preferably one who focuses on international medicine or infectious diseases. A specialist may be able to recognize and treat your illness faster. Be sure to let your doctor know what areas you've visited.
The viruses that cause viral hemorrhagic fevers live naturally in a variety of animal and insect hosts — most commonly mosquitoes, ticks, rodents or bats.
Each of these hosts typically lives in a specific geographic area, so each particular disease usually occurs only where that virus's host normally lives. Some viral hemorrhagic fevers also can be transmitted from person to person.
The route of transmission varies by specific virus. Some viral hemorrhagic fevers are spread by mosquito or tick bites. Others are transmitted by contact with infected blood or semen. A few varieties can be inhaled from infected rat feces or urine.
If you travel to an area where a particular hemorrhagic fever is common, you may become infected there and then develop symptoms after you return home. It can take up to 21 days for symptoms to develop.
Diagnosing specific viral hemorrhagic fevers in the first few days of illness can be difficult because the initial signs and symptoms — high fever, muscle aches, headaches and extreme fatigue — are common to many other diseases.
To help with diagnosis, your doctor is likely to ask about your medical and travel history and any exposure to rodents or 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 possible sources of infection.
Laboratory tests, usually using a sample of your blood, are needed to confirm a diagnosis. Because viral hemorrhagic fevers are particularly virulent and contagious, these tests are usually performed in specially designated laboratories using strict precautions.
Viral hemorrhagic fevers can damage your:
In some cases, the damage is severe enough to cause death.
Preventing viral hemorrhagic fevers, especially in developing nations, presents enormous challenges. Many of the social, economic and ecological factors that contribute to the sudden appearance and spread of infectious diseases — war, displacement, destruction of habitat, lack of sanitation and proper medical care — are problems that have no easy solutions.
If you live in or travel to areas where viral hemorrhagic fevers are common, take precautions to protect yourself from infection.
The yellow fever vaccine is generally considered safe and effective, although in rare cases, serious side effects can occur. Check with the Centers for Disease Control and Prevention about the status of the countries you're visiting — some require certificates of vaccination for entry. The yellow fever vaccine isn't recommended for children under 9 months of age or for pregnant women, especially during the first trimester. Vaccines for several less common types of viral hemorrhagic fevers are currently in development.
Do your best to avoid mosquitoes and ticks, especially when traveling in areas where there are outbreaks of viral hemorrhagic fevers. Wear light-colored long pants and long-sleeved shirts or, better yet, permethrin-coated clothing. Don't apply permethrin directly to the skin. Avoid unnecessary activities at dusk and dawn when mosquitoes are most active and apply mosquito repellent with a 20 to 25 percent concentration of DEET to your skin and clothing. If you're staying in tented camps or local hotels, use bed nets and mosquito coils.
If you live in an area where there are outbreaks of viral hemorrhagic fevers, take these steps to prevent rodent infestations in your home:
Simply living in or traveling to an area where a particular viral hemorrhagic fever is common will increase your risk of becoming infected with that particular virus. Several other factors can increase your risk even more, including: