Coronavirus and Super-Spreaders: What the CDC Wants You to Know

Coronavirus cases have appeared in the U.S., and there may be super-spreaders in Asia. What CDC and health experts want you to know.

The outbreak of a new coronavirus in China is continuing to spread, and so far 29 cases have been confirmed in the United States. Roughly 100 additional cases are currently under investigation by the Centers for Disease Control and  Prevention (CDC), which anticipates there will be more U.S. cases of this serious respiratory infection in the days and weeks to come.

While the news is alarming, the federal agency urges Americans not to panic.

“I do believe that right now the risk to the American public is low,” says Nancy Messonnier, MD, director of the CDC’s National Center for Immunization and Respiratory Diseases. “However, we do expect cases here and we expect to see human-to-human transmission.”

The number of people infected by the virus is approaching 100,000 worldwide, and it has killed more people than SARS at this point—1,800 and counting, most of them in China.

The new virus, known as COVID-19, is concerning precisely because it’s new. “We are in the very early stages and some of the details and facts we would like to know are not quite available,” says Robert Kim-Farley, MD, professor-in-residence at the UCLA Fielding School of Public Health.

Also of concern is the emergence of potential super-spreaders—people who seem to be more infectious and cause more infections than experts would predict.

This is what the CDC and other experts want you to know about the new virus, and the role super-spreaders can play in outbreaks:

What is a coronavirus?

Coronaviruses are a family of viruses that can cause various respiratory illnesses, including the common cold. According to a recent article in the Journal of the American Medical Association (JAMA), coronavirus accounts for 10 percent to 30 percent of all adult upper respiratory infections.

This group of viruses is actually found more often in animals, including bats, cats, and camels, according to the CDC. “What usually happens is that the virus will infect an animal then evolve and infect humans so there’s potential for human-to-human spread,” says Miriam A. Smith, MD, chief of infectious disease at Northwell Health’s Long Island Jewish Forest Hills in Queens, New York.

There are seven basic types of coronavirus that affect humans. Four usually cause mild illness. Three are more ominous and all jumped from animals, according to the CDC. One was severe acute respiratory syndrome (SARS), which originated in China. The other was Middle East respiratory syndrome (MERS) which appeared in Saudi Arabia in 2012. The third is the current outbreak.

Where did the current outbreak originate?

Epidemiologists have traced the current outbreak of illness to a busy seafood and poultry market in Wuhan, the capital of Hubei Province in Central China. According to the JAMA article, Chinese officials announced the outbreak on December 31, 2019.

No one knows which animal might have been responsible for the outbreak, but interest is centering on snakes, says William Schaffner, MD, an infectious diseases specialist with Vanderbilt University Medical Center in Nashville, Tennessee. There’s also some speculation about bats, which is intriguing, says Dr. Schaffner, because both MERS and SARS were ultimately linked to bats.

So far, the outbreak is still centered in Wuhan City but has moved to other parts of China. In addition to the cases in the United States, patients have been diagnosed in other areas of Asia, namely Hong Kong, Macao, Taiwan, Japan, Korea, Thailand, Singapore, and Vietnam, according to The Centre for Health Protection of the Department of Health of Hong Kong.

What are the symptoms?

Coronaviruses affect the respiratory system so symptoms can be similar to the cold or flu. This can include cough, fever, sore throat, runny nose, headache, and malaise (overall feeling of being unwell), reports the CDC. But symptoms do vary with the current virus mainly showing up as fever, cough, and shortness of breath, says Dr. Messonier. MERS caused respiratory symptoms (50 percent to 89 percent of patients needed help breathing through mechanical ventilation) but also gastrointestinal problems and kidney failure, according to the JAMA article. Like the current coronavirus, SARS patients had fever, cough, and shortness of breath, but some also had watery diarrhea. Up to a third of SARS patients needed mechanical ventilation. Some people with the Wuhan coronavirus have had pneumonia (in which the virus affects the lungs), says. Dr. Messonier. (Here are signs that your common cold is something worse.)

coronavirus and super spreadersvisualspace/Getty ImagesHow serious is the current virus?

Here’s a bit of good news: So far, the COVID-19 does not appear to be as deadly as SARS or MERS, says Dr. Schaffner. The fatality rate for MERS was 36 percent, and it was 10 percent for SARS, the JAMA authors stated. The fatality rate for the Wuhan coronavirus stands at about 2 percent, says Dr. Messonier, although that will likely change. In general, the deaths have been in people with pneumonia—often the elderly or people who had an underlying medical condition. “The virus obviously has the potential to kill people,” says Dr. Kim-Farley of UCLA, who was on loan to the World Health Organization because of previous service as an employee of the CDC for 18 years.

How is COVID-19 spread?

Scientists are still figuring this out.”The assumption is that the outbreak was initially based on exposure to a live animal market,” says Dr. Smith. “Now the virus appears to be spreading from human to human, but we don’t yet know how or how easily,” she says.

“It’s early days, but the assumption is that transmissibility is going to be somewhere between SARS and MERS,” says Wes Van Voorhis, MD, PhD, director of the Center for Emerging and Re-emerging Infectious Diseases (CERID) at the University of Washington. Although both of these coronaviruses had high mortality rates, SARS was easily transmittable while MERS did not spread as easily, says Dr. Schaffner.

In general, coronaviruses are spread from person to person through respiratory droplets—either through the air or if you touch a surface that has the virus on it, says Dr. Messonier. “Right now, we don’t know if this is how the Wuhan virus is spreading. We also don’t know if you have to be in close, face-to-face contact for it to spread, or if more casual contact is enough,” says Dr. Schaffner.

What is a “super-spreader”?

This term refers to a person (or animal) who can spread the virus more efficiently to other people. “Their cough and sneeze seem to be more effective,” says Dr. Kim-Farley.

The super-spreader label was first coined in 2005 by doctors investigating a SARS outbreak: They used it to describe certain people with the virus who infected an unexpectedly high number of others, forcing epidemiologists to redo their models of expected transmission. Researchers have also found super-spreaders in outbreaks of the MERS, Ebola, and Marburg viruses, among others.

Doctors may have identified a potential super-spreader in the current outbreak: A patient in Wuhan infected 15 healthcare workers in a hospital—which would certainly count as a superspreader, says Dr. Schaffner. Still, super-spreaders are relatively rare in outbreaks, he adds.

“The assumption is that super-spreaders are a little different immunologically, especially that their innate immunity that helps control the virus,” says Dr. Van Voorhis, who is also director of the Biomedical Interventions Group, part of the Megacenter for Pandemic Diseases Preparedness and Global Health Security, which will be working on vaccines, treatments, and ways to diagnose the new virus. “Super-spreaders have higher virus levels, presumably shedding more virus.”

Bear in mind, though, that the supposed super-spreader in China was ill and in contact with healthcare workers before the virus had been recognized, says Dr. Kim-Farley. “The guard was down, so to speak,” he says.

Can doctors diagnose the virus?

Within two weeks of announcing the outbreak, scientists in China had identified the culprit as a coronavirus and posted the genetic sequence online. Thanks to that quick work, the CDC came up with a gene reaction test for the virus. “It’s a much more efficient way of doing things,” says Dr. Messonier. “It takes four to six hours.” Serendipitously, the test became available just before the first U.S. patient turned up. Right now, samples need to be shipped to the CDC to be confirmed, but the CDC is working on kits that can be distributed to public health departments around the country. “We have a network of laboratories that we work with and the goal is to get the test near the patient,” Dr. Messonier says. It will also be distributed globally.

Are there treatments or vaccines?

Right now there’s no specific treatment for COVID-19, although researchers are racing to develop one. In the meantime, patients are getting supportive care, such as making sure they’re getting enough oxygen and staying hydrated, says Dr. Kim-Farley,

To prevent the spread of the virus, “we’re relying on the age-old tools of isolation and quarantine,” explains Dr. Kim-Farley. Isolation is when a patient with symptoms is put in a negative-pressure room in the hospital (the air pulls in when the door opens instead of out). Those who have been in contact with the virus and are at risk are kept in quarantine, likely staying at home and being monitored by a public health department.

Efforts are also underway to develop a vaccine, according to the National Foundation for Infectious Diseases (NFID).

What are the CDC and other health experts doing?

The World Health Organization convened an emergency meeting on January 22 but decided it was too early to declare a “Public Health Emergency of International Concern,” though members will continue to meet and re-evaluate the situation.

As of January 17, the CDC started screening passengers from Wuhan at several major U.S. airports for fever and other symptoms. They also raised the travel notice for Wuhan as a destination to Level 3: Avoid Nonessential Travel. A Level 1 notice (Practice Usual Precautions) is in place for the rest of China. CDC experts are tracing contacts of the U.S. patients in addition to developing and disseminating the rapid testing kit. China has limited travel for more than 35 million people, including closing airports. The limits come at an inopportune time, as Chinese Lunar New Year begins on January 25. (Here are some general healthy travel tips.)

What are hospitals doing?

Many if not most or all hospitals in the United States have already implemented emergency preparedness measures. Vanderbilt University Medical Center changed emergency room, hospital, and clinic prompts so that any patients with respiratory symptoms are asked whether they’ve been to China or had any contact with someone who has. Northwell facilities in New York have made similar changes. If a patient answers “yes,” hospital staff will give them a mask and place the patient in isolation. “They’re wheeled into a negative-pressure room and providers put on personal protective equipment,” says Dr. Smith. (Here are ways to avoid getting respiratory illnesses like the flu or a cold.)

What can you do to protect yourself and those around you?

Based on the information we have now, you should take the same precautions you would take to avoid getting a cold, the flu, or any other infectious diseases year-round. The experts view the virus as a respiratory infection, so follow smart anti-infection practices that you would year-round: “Cover your cough and wash your hands regularly,” says Dr. Messonier. If you do feel sick, avoid contact with other people and immediately call your doctor. Don’t go to a doctor’s office or hospital before calling first, says the NFID. That’s what the Washington State patient did when he realized he was at risk and had symptoms.

Despite the frightening nature of this news, remember that the biggest viral danger facing Americans right now is still the flu—and it’s not too late to get your flu shot.

Popular Videos


Amanda Gardner
Amanda Gardner is a freelance health reporter whose stories have appeared in,,, WebMD, HealthDay, Self Magazine, the New York Daily News, Teachers & Writers Magazine, the Foreign Service Journal, AmeriQuests (Vanderbilt University) and others. In 2009, she served as writer-in-residence at the University of Wisconsin School of Medicine and Public Health. She is also a community artist and recipient or partner in five National Endowment for the Arts grants.