Tissues from 12 carcasses found in Kazakhstan, Azerbaijan, and Turkmenistan were examined for morbillivirus nucleic acid. Sequences from the examination showed that canine distemper virus, which is part of the genus "Morbillivirus", was the primary cause of death. The sequences also proved that seals from widely separated regions of the Caspian Sea were infected by the same virus. This finding established spatial and temporal links between the seal deaths in these regions. The sequences were also identical to that of canine distemper virus found in the brain tissue of a seal that died in 1997 and showed no morbillivirus lesions. This suggests persistence of canine distemper virus in the Caspian seal population over a span of several years or repeated spillover from the same terrestrial reservoir.