I wash my hands. I know the inside of my house is clean, because the only people in here are my girlfriend and myself, and we’re both still healthy. But people who live upstairs — and this is a two-apartment building — we have agreed that we will tell each other if any of us has a fever or a cough, and we keep some alcohol wipes in the front hall to wipe down the doorknob, light switch, and other surfaces we might both touch, just to make sure that there’s no possibility of us passing it back and forth to each other. I know it sounds kooky, but this is actually the way the disease gets transmitted. You don’t have to be a crazy germaphobe. Or actually, at a time like this, it helps to be a crazy germaphobe just by instinct. And here. I’ll wash my hands in front of you so that you know that my hands are clean. But the danger with somebody else is, of course, that they’re coughing. But I’m not. I’m fine.

I wanted to ask you. We heard you, yesterday, sanitizing the studio. What do you do when you come home?

Yeah. You probably should, as much for your protection as for mine. It depends on what you put your hands on.

Today, now that the coronavirus has gone from an epidemic to a pandemic, and both infections and deaths from the disease are surging across the world and the United States, we return to Times science reporter, Donald G. McNeil, Jr., who has covered the story from the start, to understand how to navigate this new reality.

being that you gave them the virus that killed them. You’ll kick yourself for the rest of your life if you did that. People who were hospitalized in China started at age 30 and went up to 70s and 80s. Yes, on average, the outcomes are better. But if you want something to worry about, you might be the person who doesn’t have a good outcome. You’re spreading a disease to your friends, your social circle. That’s something you ought to feel guilty about. It’s not something you ought to feel indifferent about. People have to take this seriously.

Do you have a parent? Do you have a grandparent? Do you want to be the vector that carries that disease to them? Do you know anybody and love anybody who’s older and might be frail? You don’t want your last memory of that person —

Donald, there’s a strong sense that very young people and people in their teens, 20s, early 30s, are at a much lower risk level for the coronavirus. And I think that’s been borne out. Correct me if I’m wrong. So do all the recommendations that we keep hearing apply as stringently to the young?

You can’t. My girlfriend and I still kiss each other. We just trust each other enough to believe we’re not infected. It’s impossible to socially distance yourself from your children. They’re going to come up and hug you. That’s why the whole idea of home quarantine — home isolation, rather — is virtually impossible.

You’ve talked about social distancing. How do you socially distance yourself from your family, from your children, from your partner, your spouse, your boyfriend, your girlfriend? Does that really work?

Yes. They’re related to all these things. But I think people get way too obsessive about numbers, about exactly how many hours or days does the virus live on a surface? Exactly how many feet do you have to stand away from somebody else? I mean, you can’t run around through life with a tape measure, trying to figure out, is 3 feet safe enough? Is 6 feet safe enough? But stay away from people who are coughing. Stay away from people who look feverish. And if you have to communicate with somebody, keep your distance. That’s what I’d say. Just generally keep your distance.

In general, I’m hearing you say that going out and interacting with other people poses risks. So I wonder if you can help us understand the calculations behind your thinking in these particular categories. Does it have to do with the lifespan of the virus? Does it have to do with recommendations around social distancing? What is the underlying logic?

Open-air is safer than enclosed, but even in open-air venues, if you’re sitting on a seat, the handles of the seat might have virus on them. The railings when you walk down to your seat might have virus on them. The ticket taker, as he takes your ticket and hands it back to you — I know it’s paranoid-sounding, but these are all the ways that virus can be transmitted in large gatherings. It’s not just the coughing. It’s the many surfaces that get touched.

How about movies, concerts — things that might be open-air, but where people are sitting quite close to each other?

Yeah, the gym. I go to a gym. I play squash, which means all I have to touch in common with the other player is the ball, and I know my partner. I would be real reluctant to start grabbing a bunch of weights, not knowing who else had touched them, grabbing a bunch of handles on machines, not knowing who had touched them. I would be reluctant to play basketball with a dozen other guys, because you can’t have 10 guys handling the same ball. If one of them is spewing virus, a virus is going to get on the ball, and then everybody’s got it on their hands.

Well, you have to have food, so go to the grocery store. Be super careful about the handle of the cart, and remember that every box you touch has been placed on that shelf by somebody who might have coughed into their hand. Now, restaurants — I did eat in a restaurant a couple of nights ago. We looked for one that was, really, pretty empty, and we sat at the bar which had just been wiped down. But as this pandemic progresses, I’ll worry more, and I’ll probably avoid going into restaurants.

I would avoid plane travel if I could help it. I have friends who were about to fly to Kentucky to visit their son, and I said, you know what? Why don’t you drive? You know where all the surfaces inside your car have been. You don’t know where all the surfaces inside that plane or that airport have been. I know it’s going to be 11 hours instead of two hours, but I’d say, do it. And that’s what they’re doing.

I don’t think it’s terribly wise. I did it yesterday to get home. I ride the subway standing up with my face close to the vent. I have one glove on my hand, one gardening glove, and I use that if I have to hold onto a rail. The other hand, I make sure, never touches a surface, and I use that for my phone. Mostly, I keep it in my pocket. And I won’t get into a crowded car. I’ll let the train go by.

Based on some of what you just said, I’m intuiting where this may be headed, but — take the bus or the subway at this moment. Is that wise?

Which is the right thing to do. That’s the right decision for a doctor to make. But those are really tough decisions for doctors.

Yeah. It’s called the reproductive number of the virus. It’s, “If I’m sick, how many people am I going to infect?” You never know the real R-naught, or the real fatality rate, or anything about a disease, until it’s completely gone through the world. So we’re never going to know the real answers to these things for at least a year or two, because they’re going to be different in Africa than they are in New York. They’re going to be different anywhere. But if you create more distance between people so that I infect, hopefully, no people, you’ve substantially slowed my part of transmitting the virus. And if you do that across the entire population, you really slow down the movement of that virus in the population. When a lot of people are infected, and a lot of people have pneumonia, a lot of people all need to get to the hospital at the same time. A lot of those people need to get on oxygen or on ventilators, and eventually you run out of ventilators. Then you’re making the triage decisions that they’re now making in northern Italy, which is to say, OK, this is Donald McNeil, 66 years old. I’ve got a choice between saving him or a 25-year-old mother of two. Goodbye, Mr. McNeil. Sorry there isn’t any time for your family to say goodbye to you, because we can’t have visitors, but that’s it. See you later.

Look, some people are going to have to go to work. Doctors have to go to work. But it’s not so much the danger. The reason the government’s asking people not to go to work is because it creates what they call social distancing. The less interactions there are between people, the less exchange of virus there is. If you slow down the virus, you change what is sometimes called R-naught. And if you get people to be more distant from each other, the virus is transmitted less.

Let me tick through a couple of what we imagine, from conversations with everybody on “The Daily” team at The Times, to be the kinds of scenarios I think people want to better understand how to approach. A bit of a lightning round here. Is it dangerous, at this moment, to keep going to work?

You have to be aware not only of people around you who are coughing, but you also have to be aware that every — basically every hard surface you touch might potentially have virus on it, unless you know it’s been cleaned since the last person that you don’t know was there might have been on it.

So far. Key word. Donald, when we first started talking to you about the coronavirus about two weeks ago, you gave us an overview of what it was, where it was headed. Since then, a lot has changed. Given the evolution of the situation, we have questions related to this new phase of the epidemic, now that it’s very much in our lives. I’m working from home. You’re working from home. So let’s start with questions about precautions for people who don’t have the virus — which, presumably, is the vast majority of us at the moment — and how we can protect ourselves from getting the virus. What kind of activities should be avoided right now?

Good. Welcome back, and thank you for letting us into your home. I know we’ve been hearing a lot from you lately, so let us know if we’re beginning to exhaust your generosity.

michael barbaro

We’ve been talking about precautions for people who don’t have the virus and want to keep it that way. I want to turn, now, to what happens if you think you might have the virus. Based on your reporting, and based on the publicly available information, what are the first signs of illness that have been reported and that people, therefore, could be looking out for?

donald g. mcneil jr.

What the Chinese found in the large study of the first 45,000 cases is that it’s not like a cold. Fever is the number-one sign. High fever, a dry cough, and then, after that, fatigue. Runny nose was only 4% of cases, and those people might have had flu or a cold at the same time. But there’s something I wanted to say that was important. I described, in our first interview, that 80% of all cases were mild, and the other 20% were either severe or critical. And that stuck in too many people’s minds as if, oh, 80% of cases are practically nothing. You don’t even have it. Maybe it’s asymptomatic. No. That’s wrong. The Chinese study that was based on — everything was either mild, severe, or critical. Mild included everything from “barely any symptoms” to pneumonia, but pneumonia not needing hospitalization or oxygen. Once you stepped over into needing oxygen, then you were severe. Once you were in organ failure, you were critical. So if people think this is a mild disease, get over that idea. I’m sorry if I contributed to the spread of that idea. I should have been much more careful in describing the whole range of symptoms that came under the term “mild.”

michael barbaro

Right. In other words, “mild” doesn’t necessarily mean mild.

donald g. mcneil jr.

Nothing like what we mean by a mild cold.

michael barbaro

When is it recommended that, no matter how mild or severe the symptoms are, a person be tested? Is there a threshold?

donald g. mcneil jr.

I don’t know if the authorities have set a threshold yet. I know what happens in pandemics is that, ultimately, you have to assume that a lot of people have the disease. And that really when you reach the point where almost everybody has it, you end up stopping even bothering to test them. You ultimately are going to assume that everybody has it, because it’s the most popular virus going around. If you have no trouble breathing, if you have got a fever that you can handle at home, then stay home and take care of it. Although that’s not the way the Chinese handled it. The Chinese said, if you think you have symptoms — and I hope we get to this point. The Chinese said, if you think you have symptoms, if you think you’re getting sick, get directed to a fever clinic, where somebody who is in protective gear can see you, and they will see you and sort out whether you have bacterial pneumonia, or flu, or whether you have coronavirus. And if you have coronavirus, you’re going to go into isolation with a lot of other people who have coronavirus. Even if you have a very mild case, you’re going to go in with all the other mild cases, because they know cases can crash. It’s a pretty common phenomenon that people are going along OK with some breathing difficulty, and then in the second week, they crash. Their oxygen saturation drops, and they need oxygen. And in those cases, in the isolation centers in China, when you might be in a gymnasium with 1,000 other people, when you crashed, they recognized it right there. There was no wait, and they would move you to a hospital.

michael barbaro

This is a bit of an ethics question, but let’s say you get into a cab, and you’re on your way to get tested for the coronavirus, or you hitch a ride with a friend. Should it be disclosed that you think you might have the virus? Should basically anyone you come in contact with be aware of your status?

donald g. mcneil jr.

Yes. You’re carrying a potentially lethal disease, so you’ve got to warn other people. There’s no ethical question about this. Unfortunately, this has been the story of I don’t know how many pandemics. How many people have lied about having a sexually transmitted disease, especially in the five minutes right before they thought they were going to get lucky, and if they disclosed what they had, they were going to ruin the moment? Unfortunately, that’s how a whole lot of sexually transmitted diseases, including H.I.V., get passed on. It takes a lot of courage to be that ethical, and I hope during this epidemic, people will.

michael barbaro

And the test itself, it remains somewhat scarce, but to the degree you know it, can you describe the test? Is it a saliva swab?

donald g. mcneil jr.

The point is to get a sample of where the virus is, so there are different ways of getting that swab. Typically, for a while, they were doing nasopharyngeal swabs, which is, basically, pushing a Q-tip so far up your nose that it feels like it’s going into your brain. But I’ve seen swabs that were just taken from the back of the throat. And I know that there are some times, when people are coughing hard, they try to get them to cough up sputum so they can test that. You want to get a sample that’s got virus from where the cells are infected. Originally, it attaches deep in the lungs, so you’re trying to get a sample from there. But once it moves up into your nose and throat, maybe you can get a sample from there. So it’s very dangerous for the person who’s trying to get the Q-tip in, or the sputum sample out, to be standing right in front of them as they do that. They have to be really protected in order to do that safely.

michael barbaro

How long do the results generally seem to be taking for these tests?

donald g. mcneil jr.

I was told that, in China, when they had the on-the-spot labs and the fever clinics, they could give you an answer in as little as four hours, but that’s ideal. There were others of seven hours. Other times, they had to send it off someplace overnight. Until recently, we’ve been having to send every sample to Atlanta. So that’s several days.

michael barbaro

Right. To the C.D.C.

donald g. mcneil jr.

Yes, to the C.D.C.

michael barbaro

Which is the least efficient version of this, it would seem.

donald g. mcneil jr.

It’s the least efficient version, but for a while, it was the only accurate version, and a positive wasn’t considered a positive until the C.D.C. had confirmed it. We’ve got to solve this testing problem. We’ve got to have it so that tests are literally right there, because you’ve got to diagnose people and then isolate them so they don’t go home and give the virus to the family, and they don’t go back to work and give the virus to their coworkers.

michael barbaro

And we are not at that phase just yet, are we?

donald g. mcneil jr.

Right now, we’re not even talking about that phase. That’s how they did it in China. Right now, we’re still talking about home isolation, and the W.H.O., the Chinese, and the South Koreans would say, that doesn’t work. That’s too dangerous. There’s no way you can isolate at home without infecting your family.

michael barbaro

The final phase of questions, Donald, are, what happens when a person has been diagnosed with the virus? You’ve told us that there really is no cure for the coronavirus. It’s going to run its course. Are there useful over-the-counter medicines that would help somebody get through this virus?

donald g. mcneil jr.

This is kind of crazy, because I don’t think it’s safe to think of it as something you can happily stay home with and treat like, oh, I’ve got the flu. You’ve got to be aware that there is the possibility of crashing. You’ve got to have a number you can call. The state should be aware that you’re a patient, that you’re in home quarantine, and there should be somebody checking in on you each day, or you should be checking in with somebody so that they say, how high is your fever? How fast are you breathing?

michael barbaro

How long can a person expect to be sick, once diagnosed?

donald g. mcneil jr.

Mild cases typically resolved themselves in two weeks. People who were on ventilators and in severe situations were usually three to six weeks.

michael barbaro

That’s a long time.

donald g. mcneil jr.

Yeah. That’s a long time. It’s a long time for one of your ventilators to be in use. Even the severe and the critical cases — most of the time, they ended in good outcomes. But for some people, death took several weeks, too. People didn’t just immediately crash and die. It would be a somewhat slow process.

michael barbaro

Donald, once you have this virus, does it confer immunity on getting the coronavirus again in the next couple weeks, next couple of years, forever?

donald g. mcneil jr.

Nobody knows about forever. Virtually all doctors assume that having recovered from this confers immunity, because that’s the norm. When you recover from a disease, you normally have immunity at least for a while.

michael barbaro

Once a person recovers from the virus, is there permanent damage? Do we know?

donald g. mcneil jr.

Some people who have gone into severe pneumonia or A.R.D.S., adult respiratory distress syndrome, yes, will have permanent damage. They’ll live, but they’ll have permanently damaged lungs. That can definitely happen.

michael barbaro

And what do we know about how the virus, long-term, affects people who I think would be, justifiably, quite anxious at this moment — pregnant women?

donald g. mcneil jr.

The small numbers of women that have been studied in China who were pregnant during this relatively short time period — there was a study that came out just a couple of days ago. Nine women all delivered healthy babies. Something like six of the women were delivered by cesarean, which doctors may have chosen to do just for the extra safety of knowing that the baby wasn’t going to be infected in the birth canal. But some of the babies were born naturally, too, and all the babies were healthy.

michael barbaro

That’s reassuring.

donald g. mcneil jr.

That’s good news it’s a very small sample, but it’s good news from what we know from the small sample. It’s really different from some other diseases.

michael barbaro

Finally, Donald, we want to tackle a few questions that we’ve observed from friends, family and from the internet that may be in the territory of rumor or half-baked theories, but that are gaining some currency. So basically, a true-or-false section here. First off, are there multiple strains of the coronavirus, and are some more dangerous than others?

donald g. mcneil jr.

No. There are slightly different variants of the coronavirus — really, variances by a couple of nucleotides. There is no evidence that one is more infectious than the other, or one is more lethal than the other. Not so far, anyway.

michael barbaro

Next. This is a seasonal virus, and it will more or less be gone in a few months.

donald g. mcneil jr.

That would be lovely, but we don’t know that. This is a new virus. We’ve never seen it in summertime, so we don’t know how it’s going to behave in summertime. Respiratory viruses like influenza tend to disappear in the summer. We don’t know what this virus is going to do in the summer, so it’s not a good idea to make predictions. That’s just wishful thinking on the part of people who say, oh, it’s all going to disappear in the summertime.

michael barbaro

And the last of these true-of-false questions, Donald. Are the media — we hear this a lot — blowing the scale of this out of proportion, given the relatively small number of infections compared with the overall populations in any given country?

donald g. mcneil jr.

Look. I ask myself this question every day, because I’m the media in this case. Normally, I get to blame the other jackals of the press for blowing things out of proportion, but this time —

michael barbaro

Not this time.

donald g. mcneil jr.