The more lethal virus strains predominantly affect the grey matter of the CNS and cause neuronal destruction. By 3 weeks, infected dogs either die or fully recover. Virus strains that cause a more delayed disease affect the white matter of the CNS, causing acute demyelination. Recovery or fatal infection may be delayed for 2-3 months.

Virus replication initially begins in lymphoid tissues. Virus reaches the CNS about 1 week after the introduction of virus-infected lymphocytes and monocytes.