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Chapter: Microbiology and Immunology: Virology, Virus: Miscellaneous Viruses

Viral Hemorrhagic Fever

Most viral hemorrhagic fevers (VHF) are caused by 12 distinct enveloped RNA viruses that belong to four families: Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae.

Viral Hemorrhagic Fever

Most viral hemorrhagic fevers (VHF) are caused by 12 distinct enveloped RNA viruses that belong to four families: Arenaviridae, Bunyaviridae, Filoviridae, and Flaviviridae. The manifestations of the disease vary depending upon the agent causing the disease. Circulatory dysfunction, increased vascu-lar permeability, and diffuse hemorrhage, however, are the serious and terminal manifestations of the disease. With recog-nition of outbreak of infection caused by Ebola virus near the city of Kikwik, Zaire (Africa), the condition has now received worldwide attention. Viral hemorrhagic fevers caused by differ-ent viruses show following features:

·           Viral agents are usually arthropod-borne. Mosquitoes are primarily responsible for transmitting the disease.

·           Person-to-person transmission may occur in many VHFs by direct contact with infected patients, their blood, or their secretions and excretions.

·           Rats and mice are the usual animal reservoirs for many of the VHFs. However, domestic livestock, monkeys, and other primates may also serve as intermediate hosts.

·           In this condition, hemorrhage is typically present in many organs, and effusions are common in serous cavities. Widespread necrosis may be present in any organ system, and varies from modest and focal to mas-sive in extent. Liver and lymphoid systems are usually involved.

Ebola and Marburg are two most important causative agents of VHFs with a mortality of 25–100%. Both viruses are found in Africa and possibly in Philippines. Zaire subtype of Ebola virus has been associated with a high rate of infection, especially in Zaire, Africa. Ebola infection during pregnancy has been con-sistently fatal. The vector responsible for transmission of Ebola virus is not known, but infected primates appear to be respon-sible. Later close contact among humans or primates appears to spread the infection. Aerosol transmission is suggested to occur in monkeys.

Incubation period of Ebola and Marburg infection varies from 2 to 14 days. Symptoms are nonspecific. An insidious or sudden onset of fever, chills, malaise, generalized myal-gias and arthralgias, headache, anorexia, and cough are some of the common symptoms. The condition may also be associated with sore throat, epigastric pain, vomiting, and diarrhea.

No specific antiviral agents are available for the treatment for Ebola or Marburg virus. Avoidance of insect bites from the vectors and that of exposure to rodent sources of infection is the most important measure for preventing the condition. Barrier nursing and needle sterilization in African hospitals are important to eliminate epidemics of Ebola and Marburg diseases.


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Microbiology and Immunology: Virology, Virus: Miscellaneous Viruses : Viral Hemorrhagic Fever |


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