There are plenty of known viruses that we don't worry about simply because we've been lucky enough to keep them contained in very localized areas. But an epidemiologist could rattle off a whole series of viruses that they would say, "if this ever gets out and blows up, we are fucked."

Much like with the AIDS epidemic or the Ebola outbreak, Hauntavirus has a slower rate of spread and avoidable vector for transmission, but a significantly higher mortality rate.

You sure you're not talking about regular hantavirus? Most strains can't transmit from person to person; they require vectors such as mice and other rodents. But the variant people are worried about is capable of spreading directly from person to person. Cruise ships and plains may make it easy to transmit viruses that require close personal contact. But they're not exactly known for their rodent infestations.