Tests were carried out on a dead seal, found at Vejbystrand in southern Sweden, over fears that the outbreak could decimate seal populations.
Authorities detected the virus in seals at a reserve on the island of Anholt between Denmark and Sweden in late June.
Previous outbreaks proved disasterous for the seal population at the Anholt reserve in 1988 and 2002, when 60 percent and 30 percent of Denmark’s seal population died respectively.
The disease also spread to other northern European countries.
Some 10,000 seals died of the virus in 2002 in Sweden, amounting to about 50 percent of the total population.
Experts say that some seals that contracted the virus, and survived during the 2002 outbreak, had been immunised, which could help limit the number of deaths.