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The term viral hemorrhagic fever (VHF) refers to a group of illnesses that are caused by several distinct families of viruses.  While some types of hemorrhagic fever viruses can cause relatively mild illnesses, many of these viruses cause severe, life-threatening disease.

Viruses associated with most VHF’s naturally reside in an animal host and are spread by insects.  For the most part, various species of rats and mice are the main reservoirs for these viruses. The viruses are restricted to those geographical areas where their host species live in.  The viruses are then spread to people by insects such as ticks and mosquitoes.  However, the hosts of some viruses remain unknown, such as Ebola and Marburg viruses.  Humans are not the natural host for any of these viruses.  Humans are infected when they come into contact with an infected animal or insect.  However, with some of these viruses, once a person is infected the virus can be spread to others.

The viruses that cause VHF are found over much of the world.  Because each virus is associated with one or more particular animal or insect host, the virus and the disease it causes are usually seen only where the host animal lives.  While people usually become infected only in areas where the host animal lives, people have become infected from an imported host (monkeys) or a person becomes infected in an area where the virus occurs and then travels elsewhere.  The viruses associated with insect vectors are most often spread when the mosquito or tick bites a human.  Some insects may spread the virus to animals such as livestock and humans become infected when they care for or slaughter the animals.  Some viruses that cause hemorrhagic fevers can spread from one person to another, such as Ebola, Marburg, Lassa and Crimean-Congo.  This type of transmission of the virus can occur directly, through close contact with infected people, their body fluids or contaminated objects such as syringes and needles.

Four distinct families of viruses that share a number of features cause viral hemorrhagic fevers. These virus families cause the following diseases.

Symptoms:

Specific signs and symptoms vary by the type of VHF, but initial symptoms often include fever, fatigue, dizziness, and muscle aches, lost of strength and exhaustion.  Patients with severe cases of VHF often show signs of bleeding under the skin, in internal organs or from the mouth, eyes or ears. However, although they may bleed from many sites around the body, patients rarely die because of blood loss.  Severely ill patients may also show signs of shock, nervous system malfunctions, coma, delirium, and seizures.  Some types of VHF are associated with kidney failure.

Treatment and Prevention:

There is no established treatment or cure for VHF’s.  Patients receive supportive therapy only. With the exception of Yellow fever, Dengue fever and Argentine hemorraghic fever, no vaccines exist that can protect against these diseases.

Because many of the hosts that carry hemorrhagic fever viruses are rodents, disease prevention efforts include:

• Controlling rodent populations
• Discouraging rodents from entering or living in homes or workplaces
• Encouraging safe cleanup of rodent nests and droppings

For hemorrhagic fever virus’s spread by insects, prevention efforts often focus on community-wide insect control.  People are encouraged to use insect repellent, proper clothing, bednets, window screens, and other insect barriers to avoid being bitten.

Those VHF viruses that can be transmitted from one person to another, avoiding close physical contact with infected people and their body fluids is the most important way of controlling the disease.

VHF’s are also a very serious threat as biological weapons.  The province of Ontario has an emergency plan in place to deal with the importation of suspected and confirmed cases of VHF.

Only the reservoir hosts for Hantavirus (deer mouse) and West Nile Fever (mosquito) are found locally in Grey and Bruce Counties.  To date, there has not been a human case of either of these illnesses. Travellers to those areas of the world where the risk of VHF is increased should check with a travel clinic for additional information.

For more detailed information, please contact your local public health department or your doctor.

* separate fact sheet available

Source: Ontario Contingency Plan for Viral Hemorrhagic Fevers

            Centers for Disease Control (CDC)

            World Health Organization (WHO)