Haemorrhagic omsk fever A98.1

Haemorrhagic fever transmitted by ticks (Dermocentor species) (arbovirosis; genus Flavivirus, family Flaviviridae). In ticks, the pathogen is transmitted transstadially and transovarially to the surrounding area. A sylvatic circulation among wild small mammals is suspected. Mites seem to play a role here. The infection is passed on through the tick bite. A direct aerogenic infection from person to person seems possible.

Host: rodent, muskrat.

First description: 1944/45 in Western Siberia (Omsk).

In 1945 and 1948 two epidemics (only in the humid forest steppes of the northern districts around Omsk) with 200 and 600 cases were described. At present no cases are reported.

Incubation period: 3-8 days.

Beginning with high fever which is biphasic in 30-50% of cases. Furthermore, chills, headache, myalgia, lymphadenitis, nosebleeds, hematemesis, melena.

On the integument the bleeding tendency is impressive with multiple hemorrhages and purpura.

In addition, there is palatal enanthema and sometimes conjunctival injection and/or epistaxis. Gastrointestinal bleeding is possible. Encephalitis is not uncommon.

1. Lin D et al (2003) Analysis of the complete genome of the tick-borne flavivirus Omsk hemorrhagic fever virus. Virology 313:81-90.
2. Pulkkinen LIA et al.(2018) Tick-Borne Encephalitis Virus: A Structural View. Viruses 10:350.
3. Volk DE et al (2006) Structure of the envelope protein domain III of Omsk hemorrhagic fever virus. Virology 351:188-195.