90-Second Read: Doctor on Cruise Ship Questions Whether He Already Had Hantavirus

But since tests aren't as "straight-forward to interpret" as one might think, "it may never be known if that illness, which others also had, was Hantavirus" or some other virus. The CDC and other labs are running tests to assess whether Kornfeld has the virus, he explained. Kornfeld acknowledged that his "faintly positive" result might indicate that he is either about to get sick or has already been ill with the virus.

Oregon oncologist Stephen Kornfeld, MD, who is at the University of Nebraska Medical Center (UNMC) in Omaha, said he and a number of other passengers experienced flu-like symptoms in early April. The night sweats and respiratory issues cleared up, but the fatigue lingered for more than 2 weeks. At the time, it seemed like an ordinary virus one catches on a ship, Kornfeld said.

Along with members of the ship's staff, Kornfeld had nasal swabs taken and frozen in early May, which were later processed in the Netherlands. That individual has since tested negative, according to HHS. Kornfeld is the only one there in a biocontainment unit.