Congo-Crimean Hemorrhagic Fever
|Common Name(s)||Congo-Crimean Hemorrhagic Fever|
|Scientific Name(s)||Nairovirus from family Bunyaviridae|
|Physical Attributes||85-110 nm spherical virus has three molecules of negative-sense single-stranded RNA|
|Geography||Eastern Europe, the Mediterranean, northwestern China, central Asia, southern Europe, Africa, the Middle East, and the Indian subcontinent|
|Mode(s) of Transmission||Contact with infected animal blood or ticks; infectious blood or body fluids; contaminated medical supplies; person-to-person is rare|
|Likely BW Form(s)||Aerosol|
|Pathology||Headache, high fever, back pain, joint pain, stomach pain, vomiting, red eyes, flushed face, a red throat, petechiae (red spots) on the palate, jaundice; in severe cases, changes in mood and sensory perception; as the illness progresses, large areas of severe bruising, severe nosebleeds, and uncontrolled bleeding; coma and shock may result|
|Host(s)||Human, domestic animals|
|Vector/Dormant Form||Ixodid (hard) ticks, especially the genus, Hyalomma, are both a reservoir and a vector|
|Incubation Period||3-12 days|
|Vaccine||No safe and avaliable vaccine; inactivated, mouse-brain derived vaccine against CCHF has been developed|
|Treatment||Primarily supportive; some benefits from antiviral drug ribavirin when virus is in vitro|
Congo-Crimean hemorrhagic fever (CCHF) is a viral disease caused by CCHF virus. The virus, first isolated in the Congo, is transmitted by ticks, principally of the genus Hyalomma, with intermediate vertebrate hosts varying with the tick species. The disease, first found in the Crimea, occurs also in the Middle East, the Balkans, the former USSR, and eastern China. In 1969 it was recognized that the pathogen causing Crimean hemorrhagic fever was the same as that responsible for an illness identified in 1956 in the Congo, and linkage of the 2 place-names resulted in the current name for the disease and the virus. Little is known about variations in the virus properties over the huge geographic area involved. Humans become infected through tick bites, crushing an infected tick, or at the slaughter of infected livestock. Even in epidemics, cases do not show narrow clustering and person-to-person spread is rare.
The length of the incubation period for illness appears to depend on the mode of acquisition of the virus. Following infection via tick bite, the incubation period is usually 1 to 3 days, with a maximum of 9 days. The incubation period following contact with infected blood or tissues is usually 5 to 6 days, with a documented maximum of 13 days.
Typical cases exhibit sudden onset of fever and chills 3-12 days after tick exposure. There is severe headache, lumbar pain, nausea and vomiting, delirium, and prostration. Fatal cases are associated with extensive hemorrhage, coma, and shock. Mortality among cases recognized as hemorrhagic fever is 15-30%;, with death occurring in the second week of illness. In those patients who recover, improvement generally begins on the ninth or tenth day after onset of illness. Convalescence in survivors is prolonged with asthenia, dizziness, and often hair loss.
Diagnosis of suspected CCHF is performed in specially-equipped, high biosafety level laboratories. Other viral hemorrhagic fevers, meningococcemia, rickettsial diseases, and similar conditions may resemble full-blown CCHF. Most fatal cases and half the others will have detectable antigen by rapid enzyme-linked immunosorbant assay (ELISA) testing of acute serum samples. IgM ELISA antibodies occur early in recovery.
Supportive therapy with replacement of clotting factors is indicated. Care should include careful attention to fluid balance and correction of electrolyte abnormalities, oxygenation and hemodynamic support, and appropriate treatment of secondary infections. Crimean-Congo hemorrhagic fever virus is sensitive to ribavirin in vitro and clinicians have been favorably impressed in uncontrolled trials. Immune globulin has also been recommended but is available only in Bulgaria. In the case of a suspected biological attack, ribavirin could be considered for prophylaxis, but there is insufficient information to make a firm recommendation for dosing.
When patients with CCHF are admitted to the hospital, there is a risk of nosocomial spread of infection. In the past, serious outbreaks have occurred in this way and it is imperative that adequate infection control measures be observed to prevent this disastrous outcome. Patients with suspected or confirmed CCHF should be isolated and cared for using barrier nursing techniques. Because of several well-defined outbreaks within hospitals, protective measures for medical personnel are an issue. The weight of evidence points to large droplets or fomites as the mediators of transmission and so strict barrier nursing is indicated and probably sufficient for the care of naturally acquired disease. The virus is aerosol-infectious and additional precautions (for example, respirators) might be considered in a biological warfare setting.
An inactivated mouse-brain vaccine is used in Bulgaria, as of 2007, there is no safe and effective vaccine.
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