Hemorrhagic Fevers and Diseases

As of 2003, the only licensed vaccine for a hemorrhagic fever is that available for yellow fever. The vaccine consists of live virus particles that have been modified so as not to be capable of growth or of causing an infection. The virus is capable of stimulating the immune system to produce antiviral antibodies. The vaccine must be taken by those who are traveling to areas of the world where yellow fever is actively present (areas of Africa and South America). The vaccine may have some potential in protecting people from the virus that causes Bolivian hemorrhagic fever.

Vaccines to Rift Valley fever are under development. But these are still undergoing testing and so are not publicly available. Vaccines have not been developed to the other hemorrhagic fevers. An antiviral drug called ribavirin shows potential against Lassa fever. Unfortunately, the drug has caused mutations in test animals. Thus, its use on humans carries a risk. In determining whether or not to administer ribavirin, the risk of its use is weighed against the urgency of the illness.

At the present time, the best treatments for hemorrhagic fevers are isolation of the infected patient and care when handling the patient. For example, health care workers should be dressed in protective clothing, including gloves and protective facemask. Also, any material or equipment that comes into contact with a patient should be sterilized to kill any virus that may have adhered to the items.

The devastating infection caused by the hemorrhagic viruses is remarkable given the very small amount of genetic material that the viruses contain. For example, Ebola viruses can produce less than 12 proteins. How the viruses are able to evade the host immune responses, and establish infections is unknown. The virus may commandeer the host's genetic material to produce proteins that it is unable to produce. Or, hemorrhagic viruses may be exquisitely designed infection machines, containing only the resources needed to evade the host and establish an infection. Sequencing of the genetic material of hemorrhagic viruses will help distinguish between these two possibilities.