Figure. Phylogenetic tree based on 400-nt sequences amplified by PCR system 1 in the nucleoprotein gene. Lymphocytic choriomeningitis virus (LCMV) sequences characterized in this study were compared with selected homologous LCMV sequences available in the GenBank database. Sequence information corresponds to virus/nature of specimen/host/GenBank accession no. (optional), except for sequences retrieved from GenBank (virus strain/GenBank accession no.). Sequences determined in this study are in bold type. The 15 sequences determined from mouse material were almost identical and most closely related to LCMV sequence corresponding to the patient cerebrospinal fluid. These 16 sequences were grouped together and were clearly distinct from other LCMV strains included in the study (Armstrong, CH, MX, WE) and from Traub and Pasteur strains (data not shown).