There are likely 10 total hantavirus cases, including one American and one French passenger who tested positive after disembarking the ship, officials said.

Of the 18 U.S. residents who were repatriated, 16 are in Nebraska: the one who tested positive is in biocontainment and the 15 who did not test positive are in quarantine, officials said. The other two U.S. residents are in Atlanta, officials said.

Additionally, nine U.S. cruise ship passengers who disembarked prior to the outbreak being discovered are being monitored by state health departments, officials said. Two are in Texas, two are in Georgia, one is in Virginia, one is in Arizona and one is in California.

Another two Americans who were exposed during air travel are in New Jersey, officials said.

-ABC News’ Youri Benadjaoud

Fifteen passengers were welcomed to the University of Nebraska Medical Center’s quarantine unit Monday morning and one person who tested positive is in the biocontainment unit, according to officials.

The quarantine unit is more like a hotel, while the biocontainment unit is patient-based care, more like a hospital, officials said.

The 15 passengers at the quarantine unit are in “good spirits,” the unit’s medical director, Dr. Mike Waldman, said.

“We’ve been doing symptom monitoring, as well as temperature checks," he said. "Everyone here is asymptomatic and ... do not have a temperature at this time. They're all resting now and we'll do further assessments later in the day, once they've had a chance to sleep."

The one person in the biocontainment unit is doing well and does not have symptoms, but is “very tired” after a “really long journey,” officials said.

The 15 in the quarantine unit will have the option to stay in Nebraska at the quarantine center for the entire 42-day monitoring period, or go home to monitor symptoms, in coordination with their state and local health departments, officials said. This will be based on whether they develop symptoms, have a support structure at home to quarantine and can contact their health department, officials said.

Besides the 16 cruise ship passengers in Nebraska, two cruise ship passengers -- who are a couple -- were flown to Atlanta “for further assessment and care," officials said. At least one of the two in Atlanta had symptoms, officials said.

The two patients in Atlanta "are under medical evaluation" at Emory University’s Serious Communicable Diseases Unit, officials said, noting that their transfer there was "contingency planning."

"That means, if we're on it, since there was symptoms involved, they want to make sure that if they turn out to actually have the hantavirus, that it makes sure that the biocontainment unit here that provides medical care doesn't take up too much space, in case it's needed by the other passengers who are currently here in the more residential section," officials said.

The Georgia Department of Public Health said, "There is no risk to the public at this time. ... DPH is also remaining actively in communication with the CDC and other partners and will continue to do so for as long as necessary as we monitor each development in the coming days and weeks.”

The “risk of hantavirus to the general public remains very, very low,” Dr. Brian Christine, Assistant Secretary for Health at the Department of Health and Human Services, said at a news conference on Monday.

The Andes variant "does not spread easily, and it requires prolonged, close contact with someone who is already symptomatic," he assured.

Even though, he said, the department has taken the situation "very seriously from the very start."

Initial genetic analyses confirmed that the hantavirus on the Hondius cruise ship is of the "known Andes variant and rule out any relevant mutations," Spanish Health Minister Monica Garcia said in a post on social media.

-ABC News’ Victoria Beaulé