NAME: Omsk haemorrhagic fever virus (OHFV).
CHARACTERISTICS: A member of the genus Flavivirus, and Flaviviridae family Footnote 3-Footnote 6. OHFV belongs to the tick-borne Russian spring-summer encephalitis virus complex Footnote 7. OHFV is a spherical, enveloped virus of 40-50 nm in diameter and has a single-stranded, positive-sense RNA genome Footnote 3, Footnote 4.
PATHOGENICITY/TOXICITY: The onset of OHF is sudden, with fever lasting 5 to 12 days Footnote 3, Footnote 5. There is often a remission of the fever, after which 30 to 50% of patients experience a second febrile phase, commonly more severe than the first Footnote 3, Footnote 5. Common symptoms include fever, headache, myalgia, and cough as well as bradycardia, dehydration, hypotension, and gastrointestinal symptoms Footnote 1-Footnote 3, Footnote 5. The haemorrhagic manifestations of OHF are typically nosebleeds, bleeding gums, vomiting of blood, blood in the lungs, and non-menstrual bleeding of the uterus, which, in most cases, are not particularly severe Footnote 1-Footnote 3, Footnote 5. During the second phase, patients can develop meningeal signs, but neurological involvement has not been reported Footnote 3. Recovery from OHF is generally slow, but sequelae are unusual Footnote 1, Footnote 3, Footnote 6. Mortality rates range from 0.5 to 3%Footnote 6, Footnote 7.
EPIDEMIOLOGY: OHFV was first recognised following several outbreaks between 1943 and 1945 in the rural Omsk district in western Siberia Footnote 4. The virus was first isolated in 1947 from the blood of a patient with haemorrhagic fever during a later epidemic Footnote 3, Footnote 7. The natural foci of OHFV are in the Omsk and Novosibirsk regions, as well as Kurgan and Tyumen, of Siberia, which are primarily forested areas and open wetlands Footnote 1, Footnote 5, Footnote 7. The typical landscape associated with OHFV is forest-steppe Footnote 1-Footnote 3, Footnote 6. The highest incidence of OHF was observed in the years following World War II, with a substantial decline in reported infections thereafter, possibly due to immunization of the population living in the endemic region Footnote 3. During the period of 1946 to 2000 at least 1344 cases of OHF were diagnosed, occurring as large epidemics, localised outbreaks, and sporadic cases, with 97% of cases in the northern forest-steppe regions Footnote 2. Cases of OHF mostly occur between April and December, with the largest outbreaks typically occurring in late autumn (September and October) following contact with OHFV infected muskrats during hunting season. Smaller outbreaks occur during peak tick activity (Dermacentor reticulatus, April; Dermacentor marginatus, August to September) Footnote 2, Footnote 3.
HOST RANGE: Humans, muskrats (Ondatra zibethica), narrow-skulled voles (Microtus gregalis), water voles (Arvicola terrestris), ticks (Dermacentor reticulatus, Dermacentor marginatus, and Ixodes apronophrus), and mosquitoes (Aedes flavenscens and Aedes subdiversus) Footnote 1-Footnote 7. Muskrats, shrews and water voles are considered to be potent amplifying hosts of OHF virus Footnote 4.
INFECTIOUS DOSE: Unknown.
MODE OF TRANSMISSION: Routes of infection are contact with the urine, faeces, or blood of OHFV infected muskrats Footnote 1-Footnote 6 and via the bite of infected ticks Footnote 1, Footnote 3-Footnote 5. Laboratory-acquired infections can occur as a result of exposure to infectious aerosols Footnote 5.
COMMUNICABILITY: There is no evidence for human-to-human transmission Footnote 5.
RESERVOIR: The reservoirs for OHFV are thought to be small insectivorous rodents such as European water voles (Arvicola terrestris), Tundra voles (Microtus oeconomus), and Eurasian Shrews (Sorex araneus) Footnote 4. Ticks (Dermacentor reticulatus, Dermacentor marginatus) are also considered a reservoir as they can transmit the virus transovarially Footnote 3, Footnote 5.
VECTORS: Ticks are the main arthropod vectors of OHFV Footnote 1, Footnote 5. The virus has also been isolated from mosquitoes, but it is not known whether they act as a vector Footnote 1, Footnote 2.
DRUG SUSCEPTIBILITY: None known.
SUSCEPTIBILITY TO DISINFECTANTS: Inactivated by 3 to 8% formaldehyde, 2% glutaraldehyde, 2 to 3% hydrogen peroxide, 500 to 5,000 ppm available chlorine, alcohol, 1% iodine, and phenol iodophors Footnote 7.
PHYSICAL INACTIVATION: Inactivated by heat (50 to 60°C for at least 30 minutes), ultraviolet light, and gamma irradiation Footnote 7.
SURVIVAL OUTSIDE HOST: Low temperatures preserve infectivity, with stability being greatest below -60°C Footnote 7.
SURVEILLANCE: Monitor for symptoms. Serological diagnosis can be performed using techniques such as ELISA, neutralisation, compliment fixation, IgM capture, RT-PCR, and haemagglutinin inhibition Footnote 5, Footnote 6.
FIRST AID/TREATMENT: There is no specific therapy for OHF, and treatment is supportive Footnote 6. Haemorrhagic symptoms can be treated with clotting factors, fresh blood transfusion, or blood plasma Footnote 6.
IMMUNIZATION: An inactivated vaccine of mouse brain origin was developed which afforded protection, but its use was suspended because of adverse reactions Footnote 5.
LABORATORY-ACQUIRED INFECTIONS: Five cases were reported up until 1980 Footnote 8.
SPECIAL HAZARDS: None.
RISK GROUP CLASSIFICATION: Risk Group 4 Footnote 10.
CONTAINMENT REQUIREMENTS: Containment Level 4 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 9.
PROTECTIVE CLOTHING: Personnel entering the laboratory must remove street clothing, including undergarments, and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashes.
OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) in combination with a positive pressure suit, or within a class III BSC line. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The integrity of positive pressure suits must be routinely checked for leaks. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities Footnote 9.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up Footnote 9.
DISPOSAL: Decontaminate all materials for disposal from the containment laboratory by steam sterilisation, chemical disinfection, incineration or by gaseous methods. Contaminated materials include both liquid and solid wastes Footnote 9.
STORAGE: In sealed, leak-proof containers that are appropriately labelled and locked in a Containment Level 4 laboratory Footnote 9.
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: December 2011
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2011