Boelke et al.
First isolation and phylogenetic analyses of tick-borne encephalitis virus in Lower Saxony, Germany
Viruses 2019, 11, 462; doi 10.3390/v11050462
Most cases of TBE in Germany have been reported from the Federal States of Bavaria and Baden-Wuerttemberg (in southern Germany), while in the Federal State of Lower Saxony (LS) in northern Germany, only sporadic cases occur, therefore, this region has been regarded as non-risk area. Early in 2019, the Robert-Koch-Institute for the first time assessed a county in LS a TBE risk area due to an increase of TBE cases in a defined area (see snapshot week 9/2019).
In 2018, 4798 ticks have been collected at two places in this county and in 730 pools tested five (0.68%) were found positive for TBE virus RNA. The minimal infection rate for TBE virus in ticks collected in LS was 1.05% in adults and 0.45% in nymphs, which is in the range published for other districts in Germany and for other European countries. Full genome analyses of the isolates from the two places (about 60 km away from each other) showed that they were closely related to each other, which is unusual for strains from natural foci separated by this distance. According to molecular phylogenetic data of the E gene, it is discussed that these isolates originate from Poland and may have been imported (by direct transportation) along the motorways E30 and A2 via Saxony in Eastern Germany (where the strain Battane shows a high genetic relationship to the strains isolated in LS) to LS. The data presented here suggest a classical east-west invasion event from Eastern Europe to Central Europe/Germany.