While Humans were minimally affected, the virus was extremely deadly to Vulcans with their copper-based blood system; death could occur within a week as the victim essentially suffocated internally. Initial symptoms included increasing lethargy as the body lost access to oxygen.
The only known treatment was strobolin, a rare, naturally-occurring substance that was only found on a few planets. A synthesized version could be administered to slow the progression of the disease, but the recipient became immune within days. Obviously, this kind of infection was considered a medical emergency, prompting coordinated delivery with multiple ships when necessary.