Agent: The Crimean Congo haemorrhagic fever (CCHF) virus is a Nairovirus, within the Bunyaviridae group. The virus was first identified in 1944 in the Crimea, and later recognized to be the same virus causing high mortality in the Congo in 1969.

Reservoir: The reservoir for CCHF virus includes hares, birds, ticks, cattle, sheep and goats.

Vector: The most common and efficient vectors for CCHF are the hard ticks of the Hyalomma genus. Infected ticks remain infected through their different development stages, and trans-ovarian (transmission of the virus from infected female ticks to offspring via eggs) as well as venereal transmission have been demonstrated among some vector species.

Transmission mode: Humans can be infected with CCHF through the bite of infected ticks, or crushing them with bare hands and through direct contact with infected blood and tissue from livestock. Human-to-human transmission may rarely occur through exposure to blood (injury with contaminated sharps or blood on non-intact skin).

Epidemiology: CCHF virus is widespread. Evidence for the virus has been found among ticks in Africa, Asia, the Middle East and Eastern Europe. Previous outbreaks have been reported in Turkey in 2001-03 (83 cases), in Kosovo and in Albania in 2001 (18 and 8 cases respectively). In 2002, 3 cases were reported in Pakistan and 38 cases in Mauritania in 2003. Between 5 and 25 cases are reported each year in Bulgaria and South Africa. Between 1999 and 2004, a total of 155 cases were reported in Iran.

The majority of cases occur in persons involved in livestock industry, e.g. agricultural workers, slaughterhouse workers and veterinarians. Healthcare workers are at risk through unprotected contact with infectious blood or body fluids.

Clinical presentation: The incubation period depends on the way in which the infection was acquired. After a tick bite, incubation is usually 1-3 days (maximum 9), while incubation after contact with blood or tissue is longer, from 5 to 6 days (maximum 13). Disease onset is sudden, with symptoms including high fever, muscle pain, dizziness, abnormal sensitivity to light and abdominal pain and vomiting. Later on, sharp mood swings may occur, and the patient may become confused and aggressive. After 2-4 days, the agitation is replaced by somnolence, depression and lassitude. There is usually evidence of hepatitis. Petechiae may progress to ecchymoses, and other hemorrhagic symptoms, generally occurring between the 3rd and 5th day. The mortality rate of CCHF is estimated to go up to 30%, with death occurring in the second week of illness. There is a prolonged convalescence.

Diagnosis: CCHF is diagnosed through the detection of IgG and IgM antibodies to the virus (by ELISA), through the detection of the viral genome (by PCR), or though virus isolation.

Treatment: Patient isolation and supportive therapy (including hemodynamic support, treatment of secondary infections …) are the main treatment strategies. Some benefit has been reported from the use of the anti-viral drug ribavirin.

'Prevention: No safe and effective vaccine is widely available for human use. Persons at risk through professional activities should be protected from tick bites using insect repellent on exposed skin and clothes. To prevent skin contact with infected tissue or blood, gloves and protective clothing should be worn. Healthcare workers should respect universal precautions to avoid occupational exposure. Persons living in endemic areas should use personal protective measures (such as repellent, inspection of skin and clothes for ticks) and avoid areas where ticks are known to be abundant during the active period of the year (spring to fall).

Persons travelling to endemic areas should take the following preventive measures to minimise the exposure to tick bites:

1. Minimise exposure, wearing light-coloured clothing (easier to see the ticks) covering arms and legs; tuck the trousers into the socks and keep the sleeves rolled down.
2. Use insect repellent on the exposed skin (e.g. DEET 30%) and on the clothes (e.g. permethrin); before using repellents, pregnant women and children under the age of 12 years should consult a physician or pharmacist.
3. Inspect the body after possible exposure, and remove ticks immediately by steady, gentle traction, using fine-tipped forceps or tweezers, protecting hands with gloves or tissue. With the forceps or tweezers, grasp the tick as close to the skin as possible, where the mouth parts of the tick enter the skin. Pull back gently but firmly, and without crushing the body of the tick. Avoid leaving mouth parts in the skin. Wash the affected area with water and soap and disinfect with colourless disinfectant. Observe the area for 30-40 days, and consult a doctor if a pustule, rash or other signs develop at the site of the bite. Do not use heat or any substance like petrol, ammoniac, etc. to remove the tick. They may cause an irritation reaction of the tick and increase the risk for infection.

Persons having travelled to the endemic areas, and presenting with symptoms after a history of tick bite, should contact their physician.