How U.S. health officials are responding to the threat of novel coronavirus

JUDY WOODRUFF: And now back to our top story: more questions today about the fate of Americans aboard two cruise ships caught up in the global

coronavirus

crisis. Amna Nawaz has the latest. AMNA NAWAZ: This is not how Cheryl and Paul Molesky envisioned their cruise vacation. CHERYL MOLESKY, IN QUARANTINE Passenger: We've been in this room at the Diamond Princess for the past 27 days. For the past 12 days, we haven't stepped foot outside this door into the hallway. AMNA NAWAZ: The Syracuse, New York couple were among more than 300 Americans quarantined on the ship in Yokohama, Japan. The ship, with 3,700 passengers and crew, has been docked in Japan for 12 days.

More than 450 people have tested positive for the

coronavirus

, making it the largest cluster of cases outside of China. But late Sunday, US

officials

evacuated 340 Americans who had been released from the ship, including the Moleskys, back to the United States. CHERYL MOLESKY: It's a little scary about the increase in people being taken off the ship with the COVID-19 virus. So, you know, it's... I think it's time to go. I think it's time to cut our losses and take off. AMNA NAWAZ: The two flights of evacuees landed earlier today at military bases in Northern California and Texas. They now face another 14 days in quarantine.

Meanwhile, the World Health Organization said it is working closely with Japanese authorities to prevent a larger outbreak. DR. SYLVIE BRIAND, World Health Organization: We need to make sure that we focus on our goal, the public

health

goal, which is to contain the virus and not to contain people, and to make sure that we can have the right balance between population

health

in Japan and other countries, but also the health of the people who are currently on this ship. AMNA NAWAZ: Late last week, the Westerdam cruise ship was finally allowed to dock in Cambodia, after five countries turned it down.

One passenger, an American, then traveled to Malaysia, where she tested positive for the virus days later. Hundreds of people released from the ship have already headed for their home countries and are being warned to self-quarantine. In China, health experts say the outbreak may be stabilizing. Some workers returned to their jobs in Beijing and Shanghai today as the cities' two-week lockdowns expired. HU SHAOLIE, Shanghai (via translator): The elevator is disinfected every two hours, and you need to take your body temperature and record it before entering that building, and then take it at another time before entering the office.

So I don't think fear is necessary. AMNA NAWAZ: The Chinese government said today that more than 10,000 patients who have been hospitalized with the virus have recovered and been discharged. GUO YANHONG, National Health Commission (via translator): Across the country except Wuhan, the number of newly diagnosed cases has decreased for 13 consecutive days. These are really good signs that our prevention and control efforts have worked very well. AMNA NAWAZ: WHO scientists are now in China, working with

officials

there to investigate the spread of the virus. The Centers for Disease Control said the decision to repatriate Americans from the ship in Japan came after a spike in the number of new coronavirus cases on board.

So how well does quarantine work? And what are the risks after those who have been isolated return to the general population? For that and more, I'm joined by Dr. William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine. Dr. Schaffner, thank you for being with us. And welcome to "NewsHour." I want to ask you how the health officials are handling these cases. When you look at the first case from a cruise ship, you have hundreds of people who decide to evacuate, fly back to the United States, even after some of them have tested positive for the virus.

Are they handling this the right way? DR. WILLIAM SCHAFFNER, Chairman, Department of Preventive Medicine, Vanderbilt University: Oh, I think our officials, Amna, are handling the circumstances very, very well. They have well-prepared places where these quarantined people will go. They are providing excellent clinical care to people who have been diagnosed with the virus. And I think we're still in the containment phase here in the United States. Let's find everyone, diagnose them quickly, and then public health can work on all contacts. So I think our officers have this under control. AMNA NAWAZ: OK, what about the rest of the world now?

We have also just told the story of that second cruise. It was allowed to dock in Cambodia. You have hundreds of passengers who have disembarked and have already gone to other places, that known case of a positive coronavirus test that we know of. What are your concerns when it comes down to it? DR. WILLIAM SCHAFFNER: Yes. Well, there, Amna, I'm a little more concerned, because there's confusion and there wasn't a consistent policy. People who have been exposed have now traveled to many parts of the world. I hope they are being identified. And I hope local public health officials will contact them and keep them under surveillance.

I'm not sure that's happening. And now we have the possibility of small individual outbreaks starting in other countries, because if those people are infected, they could start chains of transmission in other countries. That would not be good. AMNA NAWAZ: So tell me a little bit about what we know about the quarantine standards. We have heard a lot from the passengers here who have had to go through that 14-day quarantine, some very emotional stories that they are also telling, a woman who says, I feel like I have lost a month of my life, after 14 days of quarantine in Japan and 14 more days back in the United States.

How is that quarantine? And do you know if other countries are standardizing it in some other way? DR. WILLIAM SCHAFFNER: I don't think there is any standardization. But I'm certainly sorry and hats off to all the people who have been in quarantine. It must be very, very boring. The rest of your life is moving on, and you can only deal with it through your iPhone, and it must be very, very difficult. Also, you are isolated or semi-isolated, so there is not much interaction with other people. It is not a very pleasant experience. You are being imprisoned by a virus.

AMNA NAWAZ: I have to ask you, Dr. Schaffner. There's a lot we still don't know about the virus, but there are a number of theories that are circulating and being shared. And I'd like to get your thoughts on them to make sure we're giving the right information to our audience. There is some skepticism, it is fair to say, around the information coming from the Chinese government, where the virus is believed to have originated, in China. And there was this moment from Arkansas Senator Tom Cotton, who gave an interview yesterday on FOX News. And he was asked about the origin of the virus.

Listen to this. SEN. TOM COTTON (R-AR): We don't know where it originated. But we know we have to get to the bottom of that. We also know that just a few miles from that food market is China's only biosafety level four superlab that investigates human infectious diseases. Now, we have no evidence that this disease originated there, but, due to China's duplicity and dishonesty from the start, we must at least ask the question. AMNA NAWAZ: Dr. Schaffner, what is your response to that? DR. WILLIAM SCHAFFNER: Well, it's a question that needs to be addressed. But I have to say that there are no scientists or public health officials around the world who think that this is a virus that somehow escaped from a containment facility.

This is a virus, just like the SARS virus and the MERS virus were, the Middle East Respiratory Syndrome viruses, these were coronaviruses that got to humans from animals. That is what happened with this case. AMNA NAWAZ: As to Senator Cotton's point though, we've heard this before. There is skepticism about the information coming from the Chinese government. Do you trust the numbers as reliable coming from the government? DR. WILLIAM SCHAFFNER: Well, the number of cases coming from China has changed over time because their case definition has changed. I think they're trying to do a good job, but it's still very confusing and we have to be skeptical.

We don't know if the outbreak in Wuhan and other parts of China is continuing at the same rate, increasing or, oh my gosh, it might be slowing down. The numbers are not consistent enough to draw firm conclusions yet. AMNA NAWAZ: Well, until that point, we just heard today that the Chinese government says that there was actually a drop in the number of cases. If that is true, what would that tell you about the possible future spread of the virus? DR. WILLIAM SCHAFFNER: Well, if that's true, and I certainly hope it is, it would mean that this huge public health experiment that they've done, quarantining between 11 and 50 million people, actually had some impact on reducing the transmission of the virus.

I have always expected that. I hope that's correct, and then we can start planning the endgame. When can we start to get things back to normal? But it is too soon to be sure that we can do it. We can hope for the best, but we have to keep preparing for the worst. AMNA NAWAZ: Dr. Schaffner, only a few seconds left. I have to ask you. Just a week ago, scientists were saying that the potential for a global pandemic still exists. Based on what we know in the last week, do you think that is still the case?

DR. WILLIAM SCHAFFNER: The potential is there, Amna. Whether we will get there or not, we don't know. I'm holding my breath and crossing my fingers. AMNA NAWAZ: Dr. William Schaffner from Vanderbilt University School of Medicine, thank you very much. DR. WILLIAM SCHAFFNER: Thank you.