President Donald Trump discussed the hantavirus outbreak on Monday, saying, "We think we're in very good shape. We're very careful."

“It’s been around for a long time," he said of the hantavirus. "People are very familiar with it. So, you know, I hope it's fine."

“All I can do is, everything that a president can do, which is something which is actually somewhat limited,” he continued.

Trump also defended his withdrawal from the World Health Organization earlier this year, saying he is “glad” he made this decision.

“No, I’m glad,” Trump said when asked if he regrets withdrawing from WHO.

“We weren't being treated well, and they were making the wrong diagnoses,” he claimed, later arguing that the organization either “lied” to him or “didn’t know.”

-ABC News’ Emily Chang

On Monday, 16 American cruise ship passengers arrived at the University of Nebraska Medical Center; 15 are in the quarantine unit and one person who tested positive is in the biocontainment unit.

Three of those passengers now in Nebraska are residents of New York, according to New York state Health Commissioner Dr. James McDonald.

“One passenger is from New York City, while the other two are residents of Orange County and Westchester County. All three are expected to be subject to a 42-day monitoring period," McDonald said in a statement.

“It is important to emphasize that there is no immediate risk to the public,” McDonald added.

Emory University Hospital said that, of the two cruise ship passengers now at its Serious Communicable Diseases Unit, one is symptomatic and is “receiving care in Emory’s biocontainment unit.”

The other passenger is asymptomatic and is “undergoing evaluation and monitoring.”

These two passengers are a couple, officials said earlier on Monday.

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

The hantavirus outbreak aboard the MV Hondius "is on the end of its run right now," a top infectious disease expert told ABC News "This Week" Sunday.

"The good news is that, in a sense, it is hantavirus and not another coronavirus or influenza virus. This is one that has very limited ability to be transmitted person to person. In fact, it's a rare exception," Dr. Michael Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), told ABC News' Martha Raddatz. "And so we have no question about the fact that this really is on the end of its run right now."

There are about 30 cases of hantavirus a year in the U.S. on average, and "they mostly occur west of the Mississippi" – about 96%, Osterholm said, due to a specific mouse that lives in that region. He also said that person-to-person transmission of the hantavirus strain in question is "a very rare exception," and only occurs when someone is exhibiting symptoms of the virus.

"Right now, you can manage the individuals who have been exposed very simply by asking them twice a day, 'are you experiencing any kind of a fever?' And then take the temperature: 'Do you have any symptoms?' If somebody is identified right at that point, you can put basically an N95 mask on and stop all transmission," Osterholm said.

"So this is why we don't need this high-tech, you know, containment facilities, et cetera, to monitor these people. We can monitor them very simply," Osterholm added, explaining why quarantining returning Americans isn't necessary.

"I have complete confidence that we will have good compliance here," Osterholm said of monitoring passengers who are returning. "And I think within days, this will no longer be a story."

-ABC News' Quinn Scanlan