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Hemorrhagic Fevers Overview
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.
How is it transmitted?
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.
Viral Hemorrhagic Fever (VHF) Facts
- Viral hemorrhagic fevers are group of illnesses caused by viruses that cause vascular damage that result in symptomatic bleeding (hemorrhage).
- Hemorrhagic fever viruses are mainly zoonotic diseases caused by viruses that usually reside in an animal or arthropod hosts that may serve as vectors.
- Viral hemorrhagic fevers are usually seen associated with only one particular of species and consequently are usually contained in geographically restricted areas; however, if the virus is introduced accidentally to humans it becomes widespread (for example, the current Ebola outbreak).
- Hemorrhagic fever viruses are usually transmitted among animal or arthropod hosts; however, the viruses carried in these animal or arthropods can be transmitted to humans when humans come in contact with the urine, feces, saliva, or other bodily fluids of infected animals or arthropods, including if the animal is killed and eaten. In some instances, once the viruses infect humans, person-to-person transmission can occur when an uninfected person comes in contact with bodily fluids or (with some viruses) a bite by an arthropod vector.
- Symptoms of viral hemorrhagic fever include fatigue, fever, weakness, dizziness, and muscle aches; patients with more severe infections show bleeding under the skin, internal organs, or even from bodily orifices like the mouth, eyes, or ears. Some patients develop severe diarrhea that may also be bloody, and severely ill patients present with shock, delirium, seizures, kidney failure, and coma that often ends in death.
- Patients with viral hemorrhagic fevers usually receive only supportive therapy; there is no other established cure for viral hemorrhagic fevers. However, ribavirin (Rebetol, Copegus) has been effective in treating some individuals with Lassa fever, and treatment with convalescent-phase plasma has been used with success in a few patients other experimental antiviral agents have also been tried in a few patients.
- Prevention and control of hemorrhagic fevers is difficult; except for yellow fever and Argentine hemorrhagic fever, no vaccines have been made commercially available so that prevention efforts are concentrated on avoiding contacts with the host species, vectors, or humans infected with the viruses.
- Scientists and researchers are addressing the threat of viral hemorrhagic fevers to humans by attempting to develop immunological, molecular, and containment methods to prevent these hemorrhagic fevers.
Viruses associated with most VHFs are zoonotic. This means that these viruses naturally reside in an animal reservoir host or arthropod vector. They are totally dependent on their hosts for replication and overall survival. For the most part, rodents and arthropods are the main reservoirs for viruses causing VHFs. The multimammate rat, cotton rat, deer mouse, house mouse, and other field rodents are examples of reservoir hosts. Arthropod ticks and mosquitoes serve as vectors for some of the illnesses. However, the hosts of some viruses remain unknown Ebola and Marburg viruses are well-known examples.
Hemorrhagic Fevers Risk factors
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:
- Working with the sick
- Slaughtering infected animals
- Sharing needles to use intravenous drugs
- Having unprotected sex
- Working outdoors or in rat-infested buildings
Scientists and researchers are challenged with developing containment, treatment, and vaccine strategies for these diseases. Another goal is to develop immunologic and molecular tools for more rapid disease diagnosis, and to study how the viruses are transmitted and exactly how the disease affects the body (pathogenesis). A third goal is to understand the ecology of these viruses and their hosts in order to offer preventive public health advice for avoiding infection.
Hemorrhagic Fevers Complications
Viral hemorrhagic fevers can damage your:
In some cases, the damage is severe enough to cause death.