This graphic shows the ecological cycle for Omsk hemorrhagic fever virus (OHFV), a member of the virus family Flaviviridae. Cases of OHF occur in the western Siberia regions of Omsk, Novosibirsk, Kurgan and Tyumen. Rodents serve as the primary host for OHFV, which is transmitted via the bite of an infected tick. Likewise, humans can become ill following an infected tick bite or through contact with the blood, feces, or urine of an infected, sick, or dead animal – most commonly, rodents. Occupational and recreational activities such as hunting or trapping may increase human risk of infection. No human-to-human transmission has been documented.