virions of a coronavirus

Coronavirus Q&A — Columbia Experts Explain What You Should Know

April 17, 2020

How can I avoid exposure to the virus?

The CDC and other public health experts recommend everyday actions—including frequent hand-washing—to help prevent the spread of respiratory diseases.

What if I think I have symptoms?

Check our information guide for patients about symptoms of COVID-19 and when and how to seek medical care.

The Do's and Don'ts of Wearing a Mask


The CDC recommends that all Americans use simple cloth face coverings to slow the spread of the virus from asymptomatic carriers to others.

Susannah Hills, MD, assistant professor of otolaryngology/head & neck surgery, provides tips in the video above about making a homemade face covering, what materials to use, and how to don, doff, and care for your mask.

If I don't have symptoms, should I wear a mask?

"Particularly since 25 to 50 percent of people with the virus are asymptomatic, it would be best for everyone to be wearing a mask or face covering when in public to protect others," Dara Kass, MD, associate professor of emergency medicine, and three other experts wrote in The New York Times on April 2.

In a randomized control trial, participants who were told to use a surgical mask, and did so, were 80% less likely to contract a respiratory illness.

Coping with COVID-19

Most people who experience COVID-19 will be able to care for themselves at home and will not need to visit their doctor or require hospitalization. David Buchholz, MD, senior founding medical director for primary care at ColumbiaDoctors, has advice:


Questions answered in the video include, how do most cases progress (0:06), when do I need to talk to a doctor or seek medical attention (1:05), and can I get tested if I think I have COVID-19 (1:56)?

Your COVID-19 Questions Answered

Columbia physicians and infectious disease experts Wafaa El-Sadr, MD, MPH, Scott Hammer, MD, and Melanie Bernitz, MD, MPH, answered viewers questions, including, when will my sense of smell return (43:29), can a flu shot reduce COVID-19 symptoms (47:08), and will antibody testing become widespread (53:41)? (Recorded April 13).


Are asymptomatic people spreading the virus?

“The bottom line is that there are people out there shedding the virus who don’t know that they’re infected,” Jeffrey Shaman, PhD, professor of environmental health sciences, told The New York Times.

Studies by his team have shown, he said, that some people never notice their symptoms, others are unable to distinguish the infection from their smoker’s cough or allergies or other conditions, the Times reported.

Shaman is the senior author of a recent report published in the journal Science that found that undetected cases, many of which were likely not severely symptomatic, were largely responsible for the rapid spread of the COVID-19 outbreak in China.

Government control efforts and population awareness, they reported, have reduced the rate of spread of the virus in China. Read more about the study here.

Are extreme social distancing measures working?

"There’s some evidence that there is some slowing in the rate of growth in certain communities," Jeffrey Shaman, PhD, told WBUR on April 1. "Certainly we’ve seen that on the West Coast in the Seattle area, and we’re just starting to see it in New York City, which is encouraging.

"What we see today as confirmed cases acquired the infection a couple weeks ago. And a couple weeks ago, some of the interventions that are in place right now in New York City were not yet in place. So we haven’t seen the effects of those terms of confirmed cases yet."

"I'm hoping that we can get it under control, but it will take some time to do that," said Stephen Morse, PhD, an expert in emerging infectious diseases at Columbia University Mailman School of Public Health, on "This Week in Virology," a podcast run by Columbia virologist Vincent Racaniello, PhD: "During wartime, we tend to have a shared sense of purpose and mission. Even though it's going to be very unpleasant for all of us to go through this, I'm hoping that we will be able to have that shared sense of purpose and realize we're doing this for each other and pull together to help ourselves.

"Because helping ourselves also helps each other. We should think in those broad terms of shared sacrifice and community effort, with that sense of mission."


What are the symptoms?

"A joint WHO-China report has some good summaries of what's happening so far," Columbia virologist Vincent Racaniello, PhD, told This Week in Virology podcast listeners on March 7. 

"Typical signs and symptoms: fever 88%; dry cough 68%; fatigue 38%; sputum production 33%; shortness of breath 18%; sore throat 13%, headache 13%; myalgia or arthralgia 15%; chills 11%; nausea or vomiting 5%; nasal congestion 5%; diarrhea 3.7 %.

"80% of infections are mild-moderate, 15% are severe, 5% are critical. About 10% to 15% of mild-moderate cases become severe; 15% to 20% of severe become critical.

"Average time from exposure to symptom onset is five to eight days." After infection, time from symptoms to recovery among mild cases is two weeks, three to six weeks for severe cases.

Why is it important to "flatten the curve?"

“The goal is to have fewer people going into the hospital or needing attention at any given time. We want to prevent the big peaks that would put a tremendous burden on health care facilities,” says Stephen Morse, PhD, professor of epidemiology at Columbia University Mailman School of Public Health and a foremost expert on emerging infectious diseases.

"If it takes longer for people to come into contact with someone who is infected," Morse says, "you would slow down the progress of the infection." Read more here.

How is the coronavirus spreading?

Inhalation of respiratory droplets is thought to be the primary mode of transmission, Jessica Justman, MD, told CUIMC News. "Respiratory droplets are made up of larger, heavier drops compared to the fine mist of an aerosol. Respiratory droplets fall to the ground within a shorter distance compared to the fine mist of an aerosol.

"Contact, or touching contaminated surfaces, is thought to be secondary, but it is still a risk. If you touch a surface with infectious virus particles on it and then touch your nose/mouth/eyes then there is a risk that the virus will cause an infection. WHO estimates the virus remains infectious from hours to days—as  long as eight to nine days—on different surfaces, depending on the surface and the surrounding temperature and humidity. It seems to last longer on hard surfaces than soft surfaces."

What is the definition of “close contact”?

"The most important way that you are likely to get infected with COVID-19 is through close contact," Jessica Justman, MD, an infectious disease physician at CUIMC and senior technical director at ICAP at Columbia, told WNYC on March 18.

"Close contact means being within four to six feet of somebody for at least 10 minutes.

"The 10 minutes comes from CDC study of people who became sick on some of the cruise ships. And what they found is that most of the cases involved contact with [a symptomatic person] for at least 10 minutes."

Is it better to shop in person or get groceries delivered?

"I think, in general, it's safer to take delivery, simply because if you go out to the supermarket, you're coming in contact with a lot of people," epidemiologist Stephen Morse, PhD, told WNYC’s Brian Lehrer on March 25. "And most of the transmission of this virus is really person to person, it's through the respiratory route.”

On the question of cleaning delivery boxes, Morse said:

“We don't have much evidence that suggests that there's a lot of viral transmission that way. I think it's just important that you keep your hands clean after you've opened that box.

"For the delivery person, obviously there are a lot of risks, and so they should be careful not just of the cardboard boxes, but especially of face-to-face contact. Six feet of social really enough to prevent anyone from getting infected.”

Listen to the full episode on WNYC.

What about take-out food?

“I think in general, the chances of getting this from cooked food, even if someone who is infected is handling it, would generally be very small," Morse told WNYC’s Brian Lehrer. "I wouldn't be concerned about that.”

What's the trajectory of the illness?

Jessica Justman, MD, an infectious disease physician at CUIMC and senior technical director at ICAP at Columbia, told WNYC on March 18:

"About 40% of cases will remain mild and never develop a pneumonia. Another 40% will have moderate illness and will develop a pneumonia. Another 15% will be severe, and the last 5% will be critical. 

"The progression from the very beginning of symptoms to more moderate illness or severe illness is generally on the order of about five days or so. 

"The guidance that's coming out of New York City Department of Health is that if you are home with mild symptoms and you're not feeling better in three to four days, you should call or text your doctor.

"If you are feeling short of breath—really not able to get enough air—and feeling very unwell. That's when you should go to an emergency room to be evaluated for a more severe pneumonia."

Can people get reinfected?

"We still don’t have the answer for that," David Ho, MD, the Clyde '56 and Helen Wu Professor of Medicine, told on March 31. "One experiment has been done in monkeys where they were given the virus. The monkeys got infected, and then after they recovered, the monkeys were given the virus a second time. That second time, the virus did not take. So that may suggest that there is immunity that protects us against reinfection."

Can I catch the virus from runners who pass within six feet?

“You have a very low likelihood of getting infected," epidemiologist Stephen Morse, PhD, told WNYC’s Brian Lehrer on March 25.

"They're always going to be exceptions—nothing is ever completely without risk—but probably for most people, it's going to be a very low risk. Be careful if you can, of course, but these very short encounters are not likely to be very major sources of spread.”

How can I tell if I'm setting sick from the coronavirus or having allergy symptoms?

"Allergy symptoms typically include itchy nose/eyes and sneezing, but no fever," Justman told CUIMC News. "COVID-19 typically presents with fever and a cough, often a dry cough."

Can young people become severely ill with COVID-19?

"There are cases of people who are in their 20s, 30s, 40s and 50s, and we don’t quite understand why a small minority of the younger folks get severely ill," David Ho, MD, the Clyde '56 and Helen Wu Professor of Medicine, told on March 31.

"It could be genetics, it could be something else, we don’t know that yet. So one should not say ‘Well, I’m young, I’m not going to have any problems,’ because you’re rolling the dice. It is true that a large majority of young people will just suffer a cold or flu-like illness and recover and do just fine, but there is a small percentage that will suffer a great deal and possibly die.”

Do older people need to take more precautions?

Daniel Winetsky, MD, an infectious diseases fellow at Columbia University Irving Medical Center, told the New York Times that he's now advising his parents "to reduce to a minimum the number of people they came into contact with. Visits with grandchildren are verboten."

“I’ve tried to frame it as, ‘Don’t cancel these things, but change to Zoom or Skype or FaceTime,’” he said.

Can I use organic products to clean surfaces?

"The EPA just put out a list of 300 household cleaners that are effective at killing this coronavirus and other viruses," Columbia pediatrician Edith Bracho-Sanchez, MD, told Tamron Hall on March 10. "Go to that list. This is not the time to use something that you’re not sure has the right concentration."


Can I use hand sanitizers on my kids?

"You can. But the mainstay of protecting ourselves right now is washing our hands," Bracho-Sanchez says. "If you're on the run—and you don't have access to a sink, warm water, and soap—it's a good option."

How does COVID-19 compare with seasonal flu?

"We're all used to the flu. We talk about it pretty casually, and the coronavirus is completely new. And things that are new make us feel afraid and anxious,” Columbia infectious disease expert Jessica Justman, MD, told WNYC on March 9.

But there’s an important difference between the flu and COVID-19.

Justman says: "The percentage of people who [die from the flu] is much, much smaller. In a typical year, it's 0.1%. I think part of what is making the coronavirus situation so unsettling is that its case fatality rate is much higher. It's somewhere in the 2% or 3% range. Last week the World Health Organization said that, according to their estimates, it was 3.4%. Many people, and I tend to agree, feel that WHO's estimate is going to be high, and it's not reflecting all of the mild cases that are out there. I'm hopeful that it will be somewhere in the vicinity of 0.5%. I don't think it's going to get down to as low as the usual flu rate of o.1%."

Is there a risk to pregnant women and their fetuses?

"There is some information about pregnant women who have COVID-19 coming from China," Columbia infectious disease expert Jessica Justman, MD, told WNYC on March 9. 

"There were about 20 cases or so. And the good news is that there was no evidence of transmission to the babies. Now, I think we have to wait for more information to come in. We are in a new epidemic, and so we have to wait for the information to come in.

"What I would just to take the usual precautions: Wash your hands, try to get extra sleep, take good care of yourself. If you can, avoid crowds, use the subway at off-peak hours. Those are all very logical things to do."

Is it possible for the virus to spread through vents in my apartment building?

"Mostly this virus is transmitted by droplets, and the evidence suggests there is not frequent aerosol transmission occurring, which would mean there's not a lot of transmission occurring through circulating air systems," Angela Rasmussen, PhD, a virologist in the Center for Infection and Immunity, told WNYC's Brian Lehrer Show on March 2.

"I would feel comfortable in my apartment if someone in my building was self-quarantined."

What is a realistic timeline for developing a vaccine?

"Eighteen months would be extremely fast, so it's not likely we will have a vaccine for this season if this problem persists," says David D. Ho, MD, founding scientific director of the Aaron Diamond AIDS Research Center and professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, in an interview with NBC New York published Feb. 28.


Ho is leading an aggressive effort at Columbia University to identify potential antiviral drugs and antibodies for use against the new coronavirus.

Will spread of the virus slow down in the spring?

"The transmission of the influenza virus, for example, has been shown to fluctuate as a function of humidity and temperature. This may also pertain in this virus, we don't know," says W. Ian Lipkin, MD, director of the Center for Infection and Immunity at Columbia University Mailman School of Health, who traveled to China in late January to get information about the new coronavirus, 2019-nCoV. "This is one of the things we would like to test. If in fact it tends to be less transmissible with increases in temperature and humidity, then we may be able to get a better handle on when this outbreak may abate. Or shift hemispheres."



Lipkin spoke about the trip and how he's trying to help scientists better understand the virus after returning from China to the United States. (The interview was recorded via Skype on Feb. 13 during the last days of Lipkin's two-week home quarantine.)

Is there anything to do to prevent infection?

“Basic hygiene is the best bet to minimize the risk of infection. Wash your hands often with soap and warm water for 20 seconds; cover your mouth and nose when you cough or sneeze (in a tissue or sleeve, not your hands); and disinfect the objects and surfaces you touch. Masks should be worn by infectious patients who are not in isolation,” says Ian Lipkin, MD, director of the Center for Infection and Immunity at the Mailman School of Public Health, in an interview with Columbia News.

“The Centers for Disease Control and Prevention advises clinicians to wear specialized masks or respirators certified by the National Institute for Occupational Safety and Health in health care settings.”

How can we prevent future outbreaks? 

“An estimated 70% of infections, including HIV/AIDS, Ebola, SARS, MERS, influenza, monkey pox, and Lyme disease, originate in wildlife,” says Lipkin in an interview with Columbia News.

“Live animal markets, where different species are often packed closely together, provide a relatively easy route for viruses to jump species and into humans. Such markets were implicated in the emergence of H5N1 influenza (avian influenza) in 1999 and SARS in 2002. The time has come for an international prohibition of the sale of wildlife at live animal markets.”

Media Contact

For the Media

Please contact to arrange an interview with our experts:

  • Dr. Edith Bracho-Sanchez, global health expert, assistant professor of pediatrics 
  • Dr. Ian Lipkin, “virus hunter,” professor of epidemiology
  • Dr. Vincent Racaniello, virologist, professor of microbiology & immunology