A doctor traveling as a passenger on the MV Hondius cruise ship has revealed how he stepped in to treat hantavirus patients after the ship’s medic was one of those sickened by the outbreak that has killed at least three people.

“I sort of fell into the role of becoming the ship doctor,” Stephen Kornfeld told CNN Thursday of his unexpected work role after the cruise ship’s primary doctor was sickened.

“I knew one of the passengers was getting ill. This is at the end of April, and I just reached out if I could assist the doc, make sure he felt he had adequate coverage,” he said of his initial offer of help, before they knew they were dealing with a spreading, deadly virus.

“And I was told the doctor was also sick. So over 12 to 24 hours, it became clear that there were a number of people sick and that they were getting sicker.”

Kornfeld, an oncologist in Bend, Oregon, said three people started to get ill around the same time — but didn’t realize their illnesses were hantavirus until last week, weeks after the first death on April 11, which at the time was assumed to be natural causes.

“Early on, we didn’t know it was hantavirus until May 2, May 3,” he said.

A Dutchman, 70, died on board the ship on April 11 and his wife, 69, died two weeks later after leaving the cruise and trying to fly out of South Africa.

Before the widow left, she showed “a lot of confusion, a lot of weakness,” but her symptoms were “non-specific,” Kornfeld said.

The unidentified ship’s doctor suffered from a “lot of fever, fatigue, and flushing” before he was removed and taken to intensive care in Johannesburg, according to Kornfeld.

“At the time, neither one of them looked critically ill. But the fear with hantavirus is you can go from seriously ill to critically ill very quickly,” he said.

Kornfeld, an avid bird watcher, told KTVZ-TV he masked up and worked 18 hours a day with limited resources as he treated sick passengers – when he should’ve been enjoying the excursion.

He noted how the ability to treat critically ill patients on the MV Hondius was “non-existent.”

“You kind of get into that doctor work mode,” he said. “You’re just trying to do the best you can in the circumstances with somewhat limited resources on a cruise. 

“I was able to find some better protective gear. I showered a lot. I washed my clothes a lot. I felt vulnerable, but I didn’t feel super vulnerable.” 

Kornfeld is one of 17 Americans on board the ship — and his representative, Janelle Bynum (D-Or.), has claimed passengers have “not received any guidance on returning home safely or disembarking the ship.”

“The seventeen Americans on board, including my constituent, are being abandoned by their government,” she claimed on X.  “They have no guidance and no support to ensure their safe return home.”

The ship is currently en route to the Canary Islands, where it is due to dock Saturday.

Meanwhile, the US Centers for Disease Control and Prevention has classified the hantavirus outbreak as a “Level 3” threat and activated its emergency operations centers, sources told ABC News Thursday.

The designation is the lowest level of emergency activation, signifying that the risk to the general public remains low — in line with information given by the World Health Organization.

The CDC is actively monitoring the situation, including by activating the emergency centers. It means that epidemiologists, scientists, and physicians may be reassigned to monitor and assist with the disease response.