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

Kevin Loria and Lauren F. Friedman

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  • The CDC says it expects the coronavirus to spread in communities in the U.S.

  • There are 57 cases in the U.S. and tens of thousands of cases around the world, with the largest number by far in China.

  • The State Department says travelers should not go to China. The CDC says travelers should reconsider travel to South Korea. Here's more info if you're now unsure about traveling overseas

  • 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 Centers for Disease Control and Prevention's announcement on Tuesday that it expects the new coronavirus will spread within communities in the U.S. was followed Wednesday by the first case here that did not involve close contact with another person known to have the virus or travel to an area with an outbreak. 

The CDC said this case, in California, could indicate that the coronavirus is spreading in a community in the U.S.

The new virus, which first emerged in Wuhan, China, at the end of last year, has already led to an international health emergency that includes a State Department “do not travel” to China advisory and quarantines for some U.S. citizens returning from high-risk areas. The CDC has said in a risk assessment that a global pandemic seems likely.

The virus can lead to a disease dubbed COVID-19, marked by respiratory problems that can range from a mild cough to severe pneumonia.

There have been at least 78,497 confirmed cases of the disease in China and 4,094 cases in other countries, according to a Johns Hopkins University database that aggregates government data. The virus has appeared in more than 40 countries, with so-called community spread reported in countries including South Korea, Italy, Iran, and Japan. There have been 2,810 deaths.

In the U.S., there have been 60 confirmed cases of the virus. Forty-two of those cases were in Americans evacuated from the Diamond Princess cruise ship, where there was a large COVID-19 outbreak; 12 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. One is the new case in California, which is of unknown origin. (The patient lives in Solano County and is receiving treatment at UC Davis Medical Center in Sacramento.)

At first, the coronavirus seemed to be largely contained in the U.S., after the government implemented quarantines, screenings, and severe travel restrictions. (More on that below.) But the CDC has now said that it's unlikely that this containment will continue, and that efforts will soon shift to trying to minimize the damage of the virus in the U.S.

In addition, the agency's limited testing—it has only tested 445 people so far—means it may not be picking up all cases. On Thursday, the CDC authorized health professionals to test people hospitalized with severe respiratory symptoms even if they have no known exposure to COVID-19 or a country where it's widespread. That may result in an uptick in the number of cases detected in the U.S.

"Ultimately, we expect we will see community spread in this country," said Nancy Messonnier, M.D., director of the CDC’s National Center for Immunization and Respiratory Diseases, in a press briefing on Tuesday. "It’s not so much a question of if this will happen anymore, but rather more a question of exactly when this will happen and how many people in this country will have severe illness."

President Trump Wednesday put Vice President Mike Pence in charge of the government's efforts to deal with the coronavirus. 

The CDC has raised its level of concern in recent days in response to the spread of the coronavirus in several countries outside of China. While officials say it's impossible to know when it might spread in communities in the U.S., Messonnier emphasized on Tuesday that people should start preparing for a potential pandemic.

"Now is the time for businesses, hospitals, communities, schools, and everyday people to begin preparing," she said. Parents should ask their children's schools if they have a plan for potential closures or dismissals; people should ask their healthcare providers what their telehealth options are; and employers should think about telework options for their employees.

"Disruption to everyday life may be severe," Messonnier added. 

Later on Tuesday, at a Health and Human Services press conference, other health officials seemed to walk back some of the CDC's earlier advice.

Anthony Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), said that Messonnier was just discussing potential actions people might need to take in the future, but that there was nothing people needed to do differently right now. "To help Americans frame what to expect, it’s helpful to think about a bad flu year," said Anne Schuchat, M.D., the CDC's principal deputy director.

Last month, the World Health Organization (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. Alex Azar, the secretary of Health and Human Services, also declared a public health emergency in the U.S.

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. 

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

What Is This New Virus?

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.)

At first, the virus was referred to simply as “2019 novel coronavirus.” Its official name—announced on Feb. 11—is 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).

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. (Though the new coronavirus has infected many more people, the fatality rate so far has been far lower than that of either SARS or MERS.)

Researchers have genetically sequenced SARS-CoV-2, and “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. 

According to the CDC, many of the first COVID-19 cases had links to a large seafood and live animal market in Wuhan.

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. That means people within 5 or 6 feet of an infected person would be the 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.

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. 

In an analysis of 138 novel coronavirus cases at one Wuhan hospital, published Feb. 7 in JAMA, doctors concluded that 57 of those people 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.

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.  

Even if there is some asymptomatic spread, most outbreaks are primarily driven by diseases spread while people show symptoms, according to Fauci, of the National Institute of Allergy and Infectious Diseases.

People who get COVID-19 appear to get sick in a time frame of a couple of days to two weeks after being exposed.  

At present, there’s no reason to think the pathogen could be transmitted through food or via consumer goods. 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. In a small percentage of cases, the disease has been fatal.

Most people who fall ill recover within two weeks. People with more severe cases generally recover in three to six weeks.  

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.

The fatality rate at the epicenter of the outbreak has so far been much higher than elsewhere in China and around the world. In Wuhan, the fatality rate has been between 2 and 4 percent; outside of Wuhan, the fatality rate has been 0.7 percent, according to the WHO.

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—though that may change. On Feb. 25, for the first time, more new cases were reported outside of China than inside of China.

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

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

For Americans, “individual risk is dependent on exposure,” the CDC says. That means for most people in the U.S., the risk according to the CDC is currently still low. But both healthcare workers and close contacts of people who develop COVID-19 are at an increased risk of becoming ill themselves.

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. 

The CDC has issued additional travel alerts. The agency now says that all travelers should avoid non-essential travel to South Korea as well as China. Meanwhile, older adults and people with chronic health conditions should also consider postponing travel to Japan, Iran, and Italy. The CDC says travelers should also reconsider any cruise ship travel to or within Asia.

In general, travelers should remain vigilant and keep up to date with the latest advisories from the CDC, Maragakis says. The CDC does not recommend masks for travelers. 

Certain airlines have suspended many flights to and from China. Airlines that have announced at least some suspensions include British Airways, Lufthansa, Air Canada, American Airlines, Delta, and United. (The airlines’ sites have more information on the specific dates of the suspensions and what to do if you have a booking. If you've already booked travel or are planning a trip, see our travel story for more specific advice.)

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. 

The more than 1,000 U.S. citizens who were evacuated from Wuhan and the Diamond Princess cruise ship by the State Department have been subject to two-week quarantines on military bases. For those flying commercial, “federal agencies coordinate with each state and local government to identify potential quarantine facilities,” according to a CDC spokesperson.

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.

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. Other measures that can protect you from the flu—like frequent handwashing and avoiding sick people—can also protect you from COVID-19. 

What Experts Still Don't Know

“Almost every day, we’re learning things we didn’t know before,” Robert Redfield, M.D., the director of the CDC 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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