Viral hemorrhagic fever (VHF)
medical conditions

Viral hemorrhagic fever (VHF)

Explore the available health information, treatment context, and integrative evidence for Viral hemorrhagic fever (VHF).

Background
  • Viral hemorrhagic fever (VHF) is a severe, often fatal, illness caused by four distinct families of viruses: arenaviruses, filoviruses, bunyaviruses, and flaviviruses. These viruses are all RNA viruses; are dependent upon a rodent, tick, or mosquito host for survival; have no drug treatment or cure, with few exceptions; and are restricted geographically to the areas where the host lives. The viruses that cause VHF are found all over the world but each virus is associated with one or more host species. Some VHF infections are rare while others affect millions of people each year.
  • VHF is spread to humans by contact with urine, saliva, or feces from infected rodents or a bite from an insect, such as a mosquito or tick. Each virus is usually associated with a specific insect or rodent host or closely related species. These animals maintain the virus and are not known to exhibit any symptoms of viral illness.
  • Some VHF organisms can enter the body by inhaled airborne particles or by direct contact with broken or chafed skin. Some arenaviruses, such as Machupo and Lassa viruses, can be spread by person-to-person contact. For example, hospital workers caring for infected individuals can acquire the infection.
  • Most VHF organisms are totally dependent on their host organism for replication and survival. The cotton rat, multimammate rat, house mouse, deer mouse, and other field rodents are examples of rodent hosts. The hosts of some VHF organisms, such as Marburg and Ebola, are currently unknown.
Risk Factors and Causes
  • Viral hemorrhagic fever (VHF) is spread to humans by contact with urine, saliva, or feces from infected rodents or a bite from an insect, such as a mosquito or tick. Some VHF organisms can enter the body by inhaled airborne particles or by direct contact with broken or chafed skin. Each virus is usually associated with a specific insect or rodent host or closely related species. These animals maintain the virus and are not known to exhibit any symptoms of viral illness. Contact with these substances and hosts therefore places individuals at higher risk of contracting VHF.
  • Travel to regions in which VHF is endemic also places individuals at higher risk. Risk may increase depending on types of activities, length of stay, and rate of transmission of a specific disease.
  • Hospital workers treating patients with VHF and laboratory researchers working with the viruses that cause VHF are also at higher risk.

  • Viral hemorrhagic fever (VHF) is spread to humans by contact with urine, saliva, or feces from infected rodents or a bite from an insect, such as a mosquito or tick. Each virus is usually associated with a specific insect or rodent host or closely related species. These animals maintain the virus and are not known to exhibit any symptoms of viral illness.
  • Some VHF organisms can enter the body by inhaled airborne particles or by direct contact with broken or chafed skin. Some arenaviruses, such as Machupo and Lassa viruses, can be spread by person-to-person contact. For example, hospital workers caring for infected individuals can acquire the infection.
Signs and Symptoms
  • All viral hemorrhagic fevers (VHF) begin gradually with flu-like symptoms that include fever, muscular aches, and cough. If the disease progresses, abdominal pain, vomiting, and diarrhea occur. The next stage involves sore throat, muscle pain, headache, chest pain, nausea and vomiting, facial swelling, conjunctivitis, or inflammation and swelling of the eyelids and portions of the eyeballs, and bleeding from the gums, intestinal tract, and other internal organs. If the disease progresses, individuals may develop temporary or permanent hearing loss, bleeding from the mouth and nose, blood in the urine, fluid in the lungs (pulmonary edema), and brain inflammation (encephalitis). In late stages, shock, seizures, coma, and death can occur.
Diagnosis
  • In many instances, humans infected with viral hemorrhagic fever (VHF) remain healthy and show no symptoms. In about 20% of cases, individuals develop severe disease that affects multiple systems of the body, including the liver, spleen, and kidneys. Hemorrhage and tissue damage may occur in these organs. This severe form of the disease has fatality rates ranging from 15% to 100%.
  • In the early stages of viral hemorrhagic fever (VHF), diagnosis is difficult because the symptoms, such as fever, muscular aches, and cough, resemble those of many other viral infections. A definite diagnosis can be made only in highly specialized laboratories. The arenavirus is composed of ribonucleic acid (RNA), which is a long chain of genetic material. The arenavirus RNA can be detected in patient specimens with a nested reverse transcriptase polymerase chain reaction (RT-PCR) assay, a laboratory procedure that is currently the most sensitive technique for detecting a specific type of RNA. In addition to identifying the RNA, this technique can determine the amount present in a sample.
Complications
  • One type of arenavirus, the lymphocytic choriomeningitis virus (LMCV), causes lymphocytic choriomeningitis (LCM). LCM infections have been reported in Europe, the Americas, Japan, and Australia. Bunyavirus, filovirus, and flavivirus infections all begin as arenavirus infections and can progress to internal bleeding.
  • Hantavirus pulmonary syndrome (PS) is a deadly disease that can cause dangerously low blood pressure (hypotension) and respiratory failure.
  • The Ebola virus is extremely deadly, having a mortality rate of 20% to 90%.
  • Flaviviruses are a family of viruses transmitted by mosquitoes and ticks. These viruses cause yellow fever, Kyasanur forest disease, Omsk hemorrhagic fever, and dengue fever. Dengue fever is one of the most common and widespread types of VHF. Fifty to 100 million cases occur worldwide each year.
Treatment
  • In the past several years, much progress has been made in understanding the molecular biology of viral hemorrhagic fever (VHF) viruses and how they cause disease. However, drugs or vaccines are currently unavailable for the treatment of most VHFs.
  • The antiviral drug ribavirin is effective for Lassa fever, which is caused by an arenavirus, if given early in the course of the disease. However, use of ribavirin is associated with birth defects. Therefore, women of childbearing age who are prescribed ribavirin should be advised to use birth control. Other antiviral drugs are under investigation for the treatment of VHF.
  • Treatment is generally aimed at the reduction of symptoms and prevention of management of complications. Treatment should ensure adequate fluids and electrolytes, maintenance of proper breathing, monitoring of kidney and bladder function, and treatment of any secondary infections.
Prevention
  • Prevention of viral hemorrhagic fever (VHF) includes avoiding mosquito bites and promoting a clean community environment that discourages rodents from entering homes. Effective measures include insecticide-soaked mosquito nets, insect repellants, full-length clothing, staying indoors between dawn and dusk, storing food in rodent-proof containers, and disposing garbage away from the home.
  • Vaccines and treatment for the vast majority of VHF infections are at present extremely limited. Current treatment primarily consists of supportive measures, such as provision of fluids and electrolytes and maintenance of normal blood pressure.
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