Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is a widespread tick-borne viral disease, a zoonosis of domestic animals and wild animals, that may affect humans. The pathogenic virus, especially common in East and West Africa, is a member of the Bunyaviridae family of RNA viruses. Clinical disease is rare in infected mammals, but commonly severe in infected humans, with a 30% mortality rate. Outbreaks of illness are usually attributable to handling infected animals or people.

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Epidemiology

  Sporadic infection of people is usually caused by Hyalomma tick bite. Clusters of illness typically appear after people treat, butcher or eat infected livestock, particularly ruminants and ostriches. Outbreaks have occurred in clinical facilities where health workers have been exposed to infected blood and fomites.

The causative organism is found in Asia, Eastern Europe, the Middle East, a belt across central Africa and South Africa and Madagascar (see map [1]) The main environmental reservoir for the virus is small mammals (particularly European hare, Middle-African hedgehogs and multimammate rats). Ticks carry the virus to domestic animal stock. Sheep, goats and cattle develop high titers of virus in blood, but tend not to fall ill. Birds are generally resistant with the exception of ostriches.

Manifestations

Typically, after a 1–3 day incubation period following a tick bite (5–6 days after exposure to infected blood or tissues), flu-like symptoms appear, which may resolve after one week. In up to 75% of cases, however, signs of hemorrhage appear within 3–5 days of the onset of illness: first mood instability, agitation, mental confusion and throat petechiae, then soon nosebleeds, bloody urine and vomiting, and black stools. The liver becomes swollen and painful. Disseminated intravascular coagulation may occur as well as acute kidney failure and shock, and sometimes acute respiratory distress syndrome.

Patients usually begin to recover after 9–10 days from symptom onset, but 30% die in the second week of illness.

Public health measures

Where mammal and tick infection is common agricultural regulations require de-ticking farm animals before transportation or delivery for slaughter. Personal tick avoidance measures are recommended, such as use of insect repellents, adequate clothing and body inspection for adherent ticks.

When feverish patients with evidence of bleeding require resuscitation or intensive care body substance isolation precautions should be taken.

The United States armed forces maintain special stocks of ribavirin to protect personnel deployed to Afghanistan and Iraq from CCHF.

Treatment

Treatment is primarily symptomatic and supportive, as there is no established specific treatment. Ribavirin is effective in vitro^[1] and has been used during outbreaks,^[2] but there is no trial evidence to support its use.

Notable outbreaks

During the summers of 1944 and 1945 over 200 cases of an acute, hemorrhagic, febrile illness occurred in Soviet troops rescuing the harvest following the ethnic cleansing of the Crimean Tatars. Virus was discovered in blood samples of patients and in the tick Hyalomma marginatum marginatum. Researchers soon recognized that a similar disease had been occurring in the Central Asian Republics. In 1969 analysis of a preserved blood sample collected from a febrile child in Zaire in 1956 showed the same virus. This finding gave rise to the present name of the disease.

On July 28, 2005 authorities reported 41 cases of CCHF in Turkey's Yozgat Province, with one death.

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