What You Need to Know About COVID-19, the New Coronavirus Disease

Kevin Loria and Lauren F. Friedman
·16 min read

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  • There are 34 cases in the U.S. and tens of thousands of cases around the world, with the largest number by far in China.

  • The U.S. government has imposed quarantines for citizens returning from the epicenter of the outbreak and has banned non-citizen visitors from China. The State Department says travelers should not go to China.  

  • The World Health Organization has declared an international health emergency, and the U.S. has declared a public health emergency.

  • The virus causes respiratory problems that can range from a mild cough to severe pneumonia.

  • This article is being updated as the situation changes. 

The coronavirus that emerged in Wuhan, China, at the end of last year has led to a global health emergency that includes a State Department “do not travel” to China advisory and quarantines for some U.S. citizens who return home from there. The virus can lead to a disease dubbed COVID-19, marked by respiratory problems that can range from a mild cough to severe pneumonia.

In China, there have already been at least 77,150 confirmed cases of the disease and at least 2,593 deaths, according to a Johns Hopkins University database that aggregates government data

There are at least 2,077 confirmed cases outside of China, according to the World Health Organization, in at least 29 different countries, with significant outbreaks outside China so far in countries including South Korea, Italy, and Japan. So far, there have been at least 33 deaths from the virus reported outside of mainland China.

In the U.S., there have been 34 confirmed cases of the virus. Eighteen of those cases were in Americans evacuated from the Diamond Princess cruise ship, where there was a large COVID-19 outbreak; eleven were in people who had traveled to China; two were in close contacts of those travelers; and three were in people flown out of Wuhan, the capital of the Chinese province of Hubei, by the U.S. Department of State.

The U.S. government has also issued strong warnings and put dramatic measures into place for American travelers.

Since Jan. 30, the State Department has had a Level 4: Do Not Travel advisory in effect, saying travelers should not go to China. Furthermore, any U.S. citizen who has been in Hubei in the previous 14 days will be subject to a mandatory 14-day quarantine upon entry. Any U.S. citizen who has been to mainland China in the previous 14 days will be screened upon entry, then subject to up to 14 days of monitored self-quarantine. And any foreign national who has been to China in the previous 14 days will be denied entry into the U.S., unless they are an immediate family member of a citizen or permanent resident. (More information for travelers, below.)

U.S. officials have also quarantined more than 1,000 citizens who were flown out of the outbreak's epicenter and from the Diamond Princess cruise ship (via Japan) on government-chartered planes.

In briefings with the media, officials from the Centers for Disease Control and Prevention (CDC) have explained why they have implemented quarantines and what they hope to accomplish—adding that these measures may change as the situation develops. 

“While we recognize this is an unprecedented action, we are facing an unprecedented public health threat,” Nancy Messonnier, M.D., director of the CDC’s National Center for Immunization and Respiratory Diseases, said on Jan. 31, after the first mandatory quarantine was announced.

“This strategy is not meant to catch every single traveler returning from China with novel coronavirus—given the nature of the virus and how it’s spreading, that would be impossible,” Messonnier said on Feb. 3, after additional travel restrictions and screenings were announced. “The goal here is to slow the entry of the virus into the United States.”

“If we take strong measures now, we may be able to blunt the impact of the virus on the United States,” Messonnier said later. “We are preparing as if this were the next pandemic.”

On Feb. 5, Messonnier called the government's actions “the beginning of what could be a long response.”

Chinese authorities, meanwhile, have shut down transit within and departing from more than a dozen cities, including Wuhan, which is home to more than 11 million people, about 650 miles south of Beijing.

On Jan. 30, the WHO declared a public health emergency of international concern, citing the new coronavirus’s spread to many countries and evidence of human-to-human transmission outside of China. The next day, Alex Azar, the secretary of Health and Human Services, declared a public health emergency in the U.S.

Currently, the spread of the new coronavirus outside of China seems to be slow, but “could accelerate,” said Tedros Adhanom Ghebreyesus, Ph.D., the director-general of WHO, Feb. 9 on Twitter. “We may only be seeing the tip of the iceberg.”

In the U.S., health officials have emphasized that currently, the risk to the general public in the U.S. remains low. Still, said the CDC’s Messonnier, “we can and should be prepared for this new virus to gain a foothold in the U.S.”

Here’s what we know so far about COVID-19.

What Is This New Virus?

The International Committee on Taxonomy of Viruses announced on Feb. 11 that what had previously been referred to as “2019 novel coronavirus” now has an official name: severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease caused by this new virus has another name, announced by the WHO the same day: coronavirus disease 2019 (COVID-19).

Both names indicate that the new pathogen is part of a large family of viruses known as coronaviruses. (Under a microscope, these viruses look like they have a crown, or corona.) 

Coronaviruses are very common in animals, and many strains affect humans, according to Thomas File, M.D., president of the Infectious Diseases Society of America (IDSA). Most known coronaviruses cause mild conditions, such as the common cold and conjunctivitis, but the new virus is not the first time a coronavirus has led to hospitalizations and deaths.

“We have seen very serious manifestations of symptoms from other novel coronaviruses such as SARS and MERS,” File says. In 2002 to 2003, an outbreak of severe acute respiratory syndrome (SARS) sickened more than 8,000 people and killed 774. Almost 10 years later, another coronavirus, known as Middle East Respiratory Syndrome (MERS), emerged and has since infected 2,499 people and killed 861.

According to a study published Jan. 23 in JAMA, the fatality rate so far for the new virus seems to be lower than that of either SARS or MERS. But it’s too soon to know for sure, File says, because there’s no accurate gauge on the number of people who are sick. Many cases—especially less serious ones—could still be unreported.

While there’s a lot that we don’t yet know about SARS-CoV-2, researchers have genetically sequenced the pathogen, which provides some context for what’s happening, what sort of virus this is, and how it may be transmitted.

“From the genetic analysis, it does look like China detected this outbreak in humans very quickly,” says Lisa Maragakis, M.D., the hospital epidemiologist at The Johns Hopkins Hospital in Baltimore and the senior director of infection prevention at The Johns Hopkins Health System. Most of the confirmed cases in humans are similar enough genetically that it doesn’t appear to have been spreading for very long—though we don’t yet know how effective steps taken to stop the spread of the illness will be, she says.

According to the CDC, many of the first COVID-19 cases had links to a large seafood and live animal market in Wuhan. Genetic analysis has shown that the new virus has some similarities to other coronaviruses that circulate in bats and snakes. 

How Does This Coronavirus Spread?

Respiratory viruses can vary greatly in terms of how quickly they spread.

Though the first cases of the new coronavirus seem to have spread from animals to people, the virus can also spread from person to person. Since those first reports, “the virus has continued to spread rapidly throughout China,” the CDC’s Messonnier said. In the U.S., however, people should know that “this virus is not spreading in your community.”

An early analysis of the first 425 confirmed cases estimated that each infected person was spreading the virus to approximately 2.2 other people, according to a study published Jan. 29 in the New England Journal of Medicine. But the authors caution that this is a preliminary number, that it’s subject to change, and that the goal of control measures is to drive this number down.

As a respiratory virus, the coronavirus is likely to spread in air droplets when someone coughs or sneezes, according to File at the IDSA. If that’s the case, people within 5 or 6 feet of an infected person are most likely to get sick. Some respiratory viruses, including others in the coronavirus family, are known to spread when people touch a surface contaminated with infectious droplets, then touch their own nose, mouth, or eyes. And some respiratory viruses also remain aloft longer and spread through the air farther, according to Maragakis, so healthcare workers have been told to wear personal protective equipment.

Although a number of healthcare workers have been infected so far—1,716 in China as of Feb. 14—we don’t have details on what protective equipment they were or weren't wearing. Messonnier, of the CDC, said that based on what scientists have seen so far, the new virus seems to mainly spread to close contacts—people within 6 feet of a patient when they cough or sneeze. There are currently no known infections among healthcare workers in the U.S.

In an analysis of 138 novel coronavirus cases at one Wuhan hospital, published Feb. 7 in JAMA, doctors concluded that 57 of those were people infected in the hospital—including 40 healthcare workers and 17 patients originally hospitalized for unrelated reasons. The significant in-hospital spread may be in part because the symptoms were not immediately recognized in some patients. Early diagnosis and isolation are key, the authors write.

With the new coronavirus, people appear to get sick in a time frame of a couple of days to two weeks after being exposed. 

Some reports have indicated that the virus may be contagious before people show symptoms. But experts who spoke to Science magazine said those reports may be flawed, in part because many people likely have mild symptoms without necessarily appearing very ill.  

Most outbreaks are primarily driven by diseases spread while people show symptoms, according to Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), who spoke at a Jan. 28 press conference.

At present, there’s no reason to think the pathogen could be transmitted through food or via consumer goods, according to a scientific risk assessment group that’s part of the German Federal Ministry of Food and Agriculture. Other coronaviruses similar to the new one don't last very long on surfaces, says the CDC, which means transmission via a surfaces after days or weeks would be highly unlikely. “There is no evidence to support transmission of 2019-nCoV associated with imported goods and there have not been any cases of 2019-nCoV in the United States associated with imported goods,” according to the CDC.

What Are the Symptoms?

There have been a wide range of symptoms so far, ranging from mild to severe. In most cases, people have had a fever and cough. In the more severe cases, people have developed pneumonia.

Based on data from roughly 17,000 reports, about 82 percent of the cases of novel coronavirus are considered mild, 15 percent are severe, 3 percent are critical, and less than 2 percent are fatal, according to Dr. Maria Van Kerkhove, an epidemiologist who shared those numbers at a WHO press briefing on Feb. 7. It's likely that those proportions will continue to change, she added.

Plus, Robert Redfield, M.D., the CDC director, emphasized at a separate press briefing on the same day that many mild cases likely remain unreported and uncounted.

Who Is at Risk?

Most of the known cases are clustered in and around Wuhan, and in people who have recently returned from the region. We’re still in the early phases of understanding which segments of the population are most at risk of infection and complications, according to Maragakis. 

In general, “elderly patients and those with underlying diseases tend to do worse with any pneumonia,” says Richard Wunderink, M.D., a professor of medicine at the Northwestern University Feinberg School of Medicine in Chicago who has written about coronaviruses. “However, younger people may be [more likely to catch the virus] for multiple social rather than medical reasons.”

Taking precautions may be especially important for “healthcare workers, who were disproportionately affected by the SARS epidemic,” Wunderink says.

For Americans, the two main risk factors are recent travel to Hubei province and close contact with people who have traveled recently to Hubei province. People who are not in one of those two groups do not need to be concerned at this point, the CDC’s Messonnier said in late January.

What Should Travelers Know About the Virus?

The State Department said on Jan. 31 that travelers should not go to China, stepping up its earlier “reconsider travel” to China message. Secretary of State Mike Pompeo cited the spread of the virus and WHO’s emergency designation in making the announcement on Twitter. 

British Airways announced on Jan. 29 that it was canceling all flights to and from mainland China, after the British Foreign Office advised avoiding all nonessential travel to the country. Later that same day, Lufthansa announced it would also suspend all flights to and from mainland China through Sunday, and Air Canada announced it would suspend all direct flights to Beijing and Shanghai through Feb. 29.

After the State Department upgraded its travel warning, American Airlines, Delta, and United announced they would temporarily suspend all regular flights to mainland China from the U.S. (The airlines’ sites have more information on the specific dates of the suspensions and what to do if you have a booking.)

In general, travelers should remain vigilant and keep up to date with the latest advisories from the CDC, Maragakis says. The CDC as of Monday has issued additional travel alerts for Japan and South Korea, saying that older adults and people with chronic medical conditions should reconsider nonessential travel.

Currently, any U.S. citizen who has been in Hubei during the previous 14 days will be quarantined upon arrival in the U.S. Anyone who has been in mainland China will be screened. And any noncitizen who has been in China during the previous 14 days will be denied entry. As of Wednesday, more than 30,000 passengers had been screened, according to the CDC. 

Passengers who were evacuated from Wuhan on government-chartered planes are being quarantined on military bases in the U.S. As of Feb. 12, there were more than 600 such passengers under quarantine, according to the CDC. (The first 195 people who were flown out completed their 14-day quarantine and were released on Feb. 11. None tested positive for the new virus.) For those flying commercial, “federal agencies coordinate with each state and local government to identify potential quarantine facilities,” according to a CDC spokesperson, who declined to specify how many people are under quarantine or where they are being housed.

The mandatory quarantines go beyond what has been put in place during previous outbreaks, such as swine flu. Health officials say that's because they learned about the new virus with enough time to try to intervene. “What was different about this one was that the outbreak was caught so early before it got to the United States,” said the CDC's Messonnier. “We had this window of time in which we could intervene and slow it down.”

Whatever restrictions the government implements, one important line of defense is travelers themselves. People who have recently traveled to an affected area should contact health officials if they notice any symptoms of infection. The CDC is distributing hundreds of thousands of educational cards to arriving travelers so that people can be on the lookout for any symptoms that might be the new coronavirus.

In the case of the first two U.S. patients identified, both had re-entered the U.S. before airport screening of those coming from Wuhan had begun. They each contacted their healthcare providers because of their symptoms and travel history.  

How Should You Protect Yourself?

If you are in or have to travel to an affected region, Maragakis says you should take the same precautions as you might for any respiratory condition: Try to avoid sick people, wash your hands frequently, cover your nose and mouth if you cough or sneeze, and try not to go out if you are sick.

The CDC does not recommend the use of face masks by the general public in the U.S., Messonnier said during a Jan. 30 media briefing.

Otherwise, although this is “the beginning of what could be a large outbreak,” she says, it’s far away from the U.S. And at this point, there have been only a relatively small number of cases outside of China. Still, the new outbreak should serve as a reminder that very severe respiratory viruses tend to circulate every few years.

“We do have tens of thousands of people who die of flu every year in this country,” she says. To protect yourself from that, she and File agree, you should get a flu shot

What Experts Still Don't Know

“Almost every day, we’re learning things we didn’t know before,” the CDC's Redfield said at a late-January press conference.

We still need to learn exactly how the virus spreads from person to person and how likely people are to get sick when they’re exposed, Maragakis says.

We also need more data to understand the mortality rate, File says.

Overall, says File, who was in China in March 2003 when WHO first issued a travel advisory for SARS, “this is almost like déjà vu.” But in this case, at least, the virus seems to have been identified much more quickly.

The CDC describes this as a “rapidly evolving situation,” and says information will be updated as it becomes available.  

Editor’s Note: This article was originally published Jan. 23. 

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