Omsk haemorrhagic fever

**Definition:** A disease caused by an infection with the Omsk haemorrhagic fever virus. This disease is characterised by fever, chills, headache, gastrointestinal symptoms and bleeding, or muscle pain with vomiting. In severe cases, this disease may also present with encephalitis. Transmission is through the bite of an infected tick, by direct contact with an infected animal, by the faecal-oral route from an infected animal, or by ingestion of milk from infected goats or sheep. Confirmation is by detection of anti-Omsk haemorrhagic fever virus antibodies in a serum sample.