Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever: A viral disease characterized by hemorrhage (bleeding) and fever.

Crimean-Congo hemorrhagic fever (CCHF) is a severe disease with a high mortality (death) rate. The geographical distribution of the virus, like that of the tick that carries it, is widespread. CCHF has been found in Africa, Asia, the Middle East and Eastern Europe.

The CCHF virus infects a wide range of domestic and wild animals that serve as reservoirs for the virus. Ticks carry the virus from animal to animal and from animal to human. The most important source for acquisition of the virus by ticks is infected small vertebrate animals on which the ticks feed. Once infected, the tick remains infected through its lifespan. The mature tick transmits the infection to large vertebrates such as livestock (cattle, sheep and goats). Humans acquire the virus from direct contact with their blood or other infected tissues from livestock during this time, or they may become infected from a tick bite. The majority of cases of CCHF have occurred in those involved with the livestock industry, such as agricultural workers, slaughterhouse workers and veterinarians.

The onset of symptoms from CCHF is sudden with fever, myalgia (aching muscles), dizziness, neck pain and stiffness, backache, headache, sore eyes and photophobia (sensitivity to light). There may be nausea, vomiting and sore throat early on, accompanied by diarrhoea and abdominal pain. Over the next few days, the patient may experience sharp mood swings and become confused and aggressive. The agitation may be replaced by sleepiness, depression and lassitude, and the abdominal pain may localize to the right upper quadrant (over top of the liver) with detectable liver enlargement. Other signs may include tachycardia (fast heart rate), lymphadenopathy (enlarged lymph nodes), and a petechial rash (a rash caused by bleeding into the skin), both on internal mucosal surfaces, such as in the mouth and throat, and on the skin. The petechiae (bleeding spots) may give way to ecchymoses (bruises, like a petechial rash, but covering larger areas) and other hemorrhagic (bleeding) phenomena such as melena (bleeding from the upper bowel, passed as altered blood in the feces), hematuria (blood in the urine), epistaxis (nosebleeds) and bleeding from the gums. There is usually evidence of hepatitis. The severely ill may develop hepatorenal (liver and kidney) failure and pulmonary (lung) failure.

The mortality (death) rate from CCHF is about 30% with death, when it occurs, usually coming in the second week of the illness. In those patients who recover, improvement generally begins on the ninth or tenth day after the onset of illness.

Diagnosis of CCHF is performed in specially-equipped biosafety laboratories by what is called enzyme-linked immunoassay (ELISA). Patients with fatal disease do not usually develop a positive ELISA test and in these individuals, as well as in patients in the first few days of illness, diagnosis is achieved by virus detection in blood or tissue samples.

Treatment involves monitoring to guide volume and blood component replacement is required. The antiviral drug ribavirin has been used with apparent benefit.

There is no safe and effective vaccine widely available for human use against CCHF. The tick vectors are numerous and widespread and tick control with acaricides (chemicals intended to kill ticks) is only a realistic option for well-managed livestock production facilities.

Persons living in endemic areas should use personal protective measures that include avoidance of areas where tick vectors are abundant and when they are active (Spring to Fall); regular examination of clothing and skin for ticks, and their removal; and use of repellents. Persons who work with livestock or other animals in the endemic areas can take practical measures to protect themselves. These include the use of repellents on the skin (e.g. DEET) and clothing (e.g. permethrin) and wearing gloves or other protective clothing to prevent skin contact with infected tissues or blood. 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. Specimens of blood or tissues taken for diagnostic purposes should be collected and handled using universal precautions. Sharps (needles and other penetrating surgical instruments) and body wastes should be safely disposed of using appropriate decontamination procedures. Healthcare workers are at risk of acquiring infection from sharps injuries during surgical procedures and, in the past, infection has been transmitted to surgeons operating on patients to determine the cause of the abdominal symptoms in the early stages of (at that moment undiagnosed) infection. Healthcare workers who have had contact with tissues or blood from patients with suspected or confirmed CCHF should be followed up with daily temperature and symptom monitoring for at least 14 days after the putative exposure.

Crimean-Congo hemorrhagic fever (CCHF) was first discovered in the Crimea in 1944. In 1956 a similar illness was identified in the Congo. And in 1969 it was recognized that the virus causing Crimean hemorrhagic fever was the same as that responsible for the illness identified in the Congo. Linkage of the 2 place-names resulted in the current name for the disease and the virus that causes it.