Crimean-Congo hemorrhagic fever (ORPHA:99827)
Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne zoonotic disease caused by CCHF virus and characterized by initial fever, headache, and malaise followed by gastrointestinal symptoms and, in severe cases, bleeding, shock, and multi-organ system failure.
Epidemiology
CCHF is endemic throughout Africa, the Balkans, the Middle East, and western Asia. Cases are usually sporadic, although small nosocomial outbreaks sometimes occur when proper infection control practices are not maintained. Around 500 cases are reported per year worldwide, although systematic surveillance is lacking.
Clinical description
The incubation period is typically 3-7 days from animal exposure and 1-3 days from a tick bite. Patients generally present with the abrupt onset of non-specific signs and symptoms including fever, malaise, headache, chest pain, and myalgia/arthralgia followed rapidly by gastrointestinal symptoms (diarrhea, nausea, vomiting) and, in some cases, rash. Severe cases develop bleeding (ecchymoses, sub-conjunctival and gastrointestinal hemorrhage), neurologic involvement (disorientation, convulsions, coma), shock, and multi-organ system failure. Mild-to-moderate leukopenia and thrombocytopenia are often noted at presentation and disseminated intravascular coagulation (DIC) commonly develops, best indicated by the presence of D-dimers.
Etiology
Over 25 different viruses cause viral hemorrhagic fever. CCHF virus is a member of the virus family Bunyaviridae, genus Nairovirus. The virus is maintained in nature in a cycle between small mammals and ticks, primarily of the Hyalomma species. Ticks also spread CCHF virus to domestic livestock, who are transiently and asymptomatically viremic. Humans are infected either by tick bites or exposure to contaminated blood or excreta of the reservoir or transiently viremic domestic animals. Farmers, abattoir workers, and veterinarians are at risk. Human-to-human transmission occurs through direct contact with blood or bodily fluids of infected persons.
Diagnostic methods
Common diagnostic modalities include cell culture (restricted to biosafety level-4 laboratories), serologic testing by enzyme linked immunosorbent assay (ELISA) or indirect fluorescent antibody (IFA) and reverse transcription polymerase chain reaction (RT-PCR). Because no commercial assays are presently available, these tests are typically only performed in a few specialized laboratories.
Differential diagnosis
CCHF is difficult to distinguish from a host of other febrile illnesses, at least early in the course of disease. Malaria, typhoid fever, leptospirosis, rickettsial infection, other viral hemorrhagic fevers (see these terms) and meningococcemia need to be excluded.
Management and treatment
Patients should be isolated and viral hemorrhagic fever precautions (face shields, surgical masks, double gloves, surgical gowns, and aprons) should be used to prevent nosocomial transmission. Although there are few controlled data, the nucleoside analogue drug ribavirin appears to be efficacious for CCHF. Otherwise, treatment generally follows the guidelines for severe septicemia. Anti-malarials and broad spectrum antibiotics should be considered until the diagnosis of CCHF can be confirmed. Persons who have unprotected contact with someone with CCHF should be monitored and post-exposure treatment with oral ribavirin considered.
Prognosis
The case-fatality rate is 15-30%. Shock, bleeding, neurological manifestations, high viremia, aspartate aminotransferase (AST) > 150 IU/L, and pregnancy confer a poor prognosis. Although convalescence may last up to a year, survivors usually have no lasting sequelae.

                            Last update: 
                            December 2012


                            - Expert reviewer(s): 
                            Dr Daniel BAUSCH  -  Andrew BENNETT