Viral Hemorrhagic Fevers

What are viral hemorrhagic fevers?

Viral hemorrhagic fevers (VHF) is a term that refers to a group of illnesses caused by several distinct families of viruses. While some types of hemorrhagic fever viruses cause illnesses that are relatively mild, many of these cause severe, life-threatening diseases with no known cures. Perhaps the most known of this group of diseases is the Ebola virus, made famous by the movie “Outbreak.”

Hemorrhagic fever viruses are caused by viruses of four distinct families:

•    arenaviruses
•    filoviruses
•    bunyaviruses
•    flaviviruses

These viruses share the following common features:

•    The viruses are geographically restricted to the areas where the host species live.
•    Their survival depends on an animal or insect host, called the natural reservoir.
•    Humans are not the natural reservoir for any of these viruses; they only become infected when coming into contact with an infected host. However, with some of these viruses, humans can transmit the virus to one another after the accidental transmission from the host.
•    They are all RNA viruses, covered in a fatty (lipid) coating.
•    With a few exceptions, there is no known cure or drug treatment for these diseases.
•    Human outbreaks or cases of these diseases occur sporadically and irregularly, making outbreaks difficult to predict.

Where have cases of viral hemorrhagic fever occurred?

The viruses that cause these illnesses are distributed globally. However, since each virus is generally associated with one or more particular host species, the virus and its ensuing disease are usually seen where the host species lives. For some species, this is a limited geographic area; however, in other cases, a particular species may be distributed worldwide.
While people usually become infected only in areas where the host lives, occasionally the host is exported from its natural habitat, causing an outbreak in a different area. Occasionally, an infected person travels from an area where the virus occurs naturally, and if it is the type of virus that can be transmitted by person-to-person contact, others then contract the disease (as was the case with the Ebola hemorrhagic fever). With more and more people traveling each year, outbreaks of these diseases are becoming a greater threat to areas where the diseases have not been seen before.
The Centers for Disease Control and Prevention (CDC) reported a large outbreak of Rift Valley fever early in 1998 in Kenya and Somalia. An outbreak occurred in southwestern Saudi Arabia and Yemen in 2000. The virus is transmitted primarily by infected mosquitoes and other biting insects and occasionally by contact with the blood or body fluids of infected animals.

Travelers are advised to take appropriate precautions to prevent infection. This includes:

•    liberal use of insect repellent.
•    wearing long sleeves and pants.
•    using bednets in areas where outbreaks are occurring.
•    avoiding contact with livestock in areas where outbreaks are occurring.
Consult your physician for more information.

Treatment for viral hemorrhagic fever:

While patients receive supportive treatment, generally there is no known cure or treatment for these illnesses. The anti-viral drug, ribavirin, has been effective in treating some persons with Lassa Fever and hemorrhagic fever with renal syndrome.