By Lena H. Sun and Miriam Berger / The Washington Post

The World Health Organization (WHO) held an emergency meeting in Geneva on Wednesday about whether to designate the outbreak of a mysterious, pneumonia-like virus that originated in China as a global health emergency. By Thursday, WHO announced that it would hold off, saying that it’s too early to make such a decision.

WHO designating the outbreak a global health emergency would help countries coordinate their responses. In the meantime, it remains a scary time for people in China and beyond as the virus and fears of contamination spread. On Tuesday, the United States confirmed its first case: a Snohomish County man who flew from China to Seattle who is in stable condition at Providence Regional Medical Center Everett.

As the news continues to develop, keep calm and catch up on what is known so far.

What is coronavirus?

According to WHO, coronaviruses are a large family of viruses that range from the common cold to much more serious diseases. These diseases can infect both humans and animals. The strain spreading in China is related to two other coronaviruses that have caused major outbreaks in recent years: Middle East respiratory syndrome, also known as MERS, and severe acute respiratory syndrome, or SARS.

Symptoms of a coronavirus infection range from respiratory problems, difficulty breathing, fever and cough, to the much more severe cases of pneumonia, kidney failure, acute respiratory syndrome (when fluid builds up in the lungs) and death. The elderly, the young and those with an already weakened immune system are at a higher risk of developing severe lower-respiratory tract diseases, such as bronchitis and pneumonia, according to the Centers for Disease Control and Prevention.

Health officials haven’t identified this latest strain in humans before. That’s why for now it has the generic name of “a novel coronavirus” while they investigate. As it’s a virus, antibiotics won’t work in treating it.

How does it spread?

In rare cases, coronaviruses can spread from animals, such as camels and bats, to humans. (Household pets are not a threat.) Health officials report that that’s what they believe has happened here. In even rarer cases, that same virus can then start to spread from human to human. That’s what happened with MERS and SARS.

WHO officials are investigating suspected cases of that now. In a worrying development, Chinese officials said Monday that they have documented cases of human-to-human transmission.

Chinese health authorities said they first detected the new strain of the virus Dec. 31 in Wuhan, a city in central China. They initially linked it to a dirty food market where seafood and mammals were sold for human consumption. (Some scientists think the source could have been snakes, though there’s no consensus yet.) Officials closed the market the next day. What probably happened, scientists said, is that people ate something infected with the virus and then became sick with it.

The next set of patients are those who reported that they did not come in contact with that market but had gone to other markets, or had contact with others in Wuhan. Chinese officials have also documented patients and health-care workers who had no contact with Wuhan.

In cases of human-to-human transmission, the disease can spread through coughing and sneezing, personal contact with an infected person, touching an infected surface and then the mouth, nose or eyes, and, in rare cases, through fecal contamination.

To protect against infection, the CDC recommends basic hygiene techniques such as constantly washing hands, staying hydrated, and coughing into one’s arm or a tissue. If there’s a fear of animal transmission, CDC officials urge people to wash hands after contact with animals and thoroughly cook any meat before consumption.

What do we know about how it has spread?

One challenge to investigating — and stopping — the virus is that public health experts say Chinese authorities have not provided information about how the disease is spreading.

To control the outbreak, it’s critical to know whether cases being found in other cities are all related to Wuhan. If the disease has been circulating independently in other parts of the country, that information will not only affect how China acts to contain it, but how other public health agencies in the world seek to prevent spread, said Tom Inglesby, director of the Johns Hopkins Center for Health Security.

The Washington Post’s Anna Fifield has reported from Beijing on cases of people dying with pneumonia-like symptoms but not being included in the death toll, suggesting “that the coronavirus could be far more prevalent than Chinese health authorities have acknowledged.”

Where has it spread?

As of Thursday evening in China, officials there said at least 17 people have died of the virus and more than 600 have been confirmed infected. That number is way up from the more than 70 infections reported Monday. Experts expect the number to keep rising amid claims that China has been underreporting cases.

So far, most cases have been in Wuhan. However, people across 14 provinces in China are being tested for the virus.

On Jan. 13, officials in Thailand confirmed what health officials feared: that a Chinese traveler who came from Wuhan to Thailand was infected. On Jan. 17, Thai officials announced that they had another infected traveler from Wuhan, according to the CDC. Days later, there was one more. On Jan. 15, Japanese officials confirmed their own case of an infected traveler from Wuhan.

“These cases did not report visiting the large seafood and animal market to which many cases in China have been linked,” the CDC reported, raising further concerns among health officials of human-to-human contamination.

Australia and the Philippines are investigating suspected cases. By Wednesday, Hong Kong and Macao confirmed their first infected patients, joining South Korea, Vietnam and Taiwan, which have each reported cases of the virus.

What’s being done to stop it in China?

On Tuesday, Chinese health authorities initially imposed a quasi-quarantine on Wuhan, limiting travel to the city, which is home to 11 million people. They did so in part because the upcoming Lunar New Year is a time when people often travel to their hometowns. That’s also why Chinese authorities may be hesitant to impose a total travel ban; they are reluctant to entirely disrupt the holiday, which is also a time of heavy commerce important to China’s economy.

Just two days later, however, Chinese authorities announced a more extreme step: As of Thursday there, they are banning all outbound travel from Wuhan, which remains the center of the outbreak.

Also on Thursday, Chinese authorities announced the closure of all large-scale Lunar New Year events in Beijing. One of China’s top tourist attractions, the Forbidden City in Beijing, said it would close “to avoid cross-infection caused by the gathering of people.”

WHO has praised China for imposing the quarantine in an effort to contain the disease. But other public health experts have questioned the effectiveness and warned that there could be negative repercussions.

“In the eyes of some public health experts, the quarantine could also cost time trying to contain the virus,” reported The Post’s Marisa Lati and Reis Thebault. “Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security, said people fleeing Wuhan to escape the restrictions make it hard for authorities to track where the virus may have spread. People who experience symptoms may also hesitate to come forward because of the government’s extreme measures to control the illness, she said.”

Their reporting continued: “Past efforts at large-scale quarantines have been largely unsuccessful. Nurses had to tend to the every need of health-care workers who were quarantined in Taiwan during the SARS outbreak, using a tremendous amount of resources, Nuzzo said. A quarantine in Liberia during the Ebola outbreak in 2014 resulted in mass upheaval, and the government quickly pivoted to a milder approach, Nuzzo said.”

Why didn’t WHO declare a public health emergency?

After deliberating, WHO announced Thursday that while there was “an emergency in China,” the outbreak did not yet rise to the level of a global health emergency, given the limited places outside of China the virus has so far spread.

“The fact that I’m not declaring a [public health emergency] today should not be taken as a sign that WHO does not think the outbreak is serious or that we’re not taking it seriously,” WHO Director General Tedros Adhanom Ghebreyesus said Thursday. “Nothing could be further from the truth. WHO is following this outbreak every minute of every day at country, regional and global levels. We’re working to prevent human to human transmission.”

Ghebreyesus also reported that one-fourth of the infected went on to develop severe symptoms, while the majority of those who died had underlying health problems already, such as hypertension or diabetes, which can weaken immune systems.

What’s happening at airports?

Chinese authorities are screening people at airports for coronavirus symptoms. Other airports in Asia are doing the same. North Korea has entirely banned foreign tourists, the majority of whom are Chinese nationals and travel via China, as a precaution.

Federal health authorities in the United States announced Friday that they will immediately begin screening passengers for the virus who are flying into three international airports popular with Chinese travelers — Los Angeles, San Francisco, and New York’s John F. Kennedy. On Tuesday, they added international airports in Chicago and Atlanta to the list.

The screening will include taking temperatures; those with high temperatures could be singled out for additional tests. While screening for a common virus usually takes hours, health authorities told The Post’s Lena Sun that people with suspected cases could miss their connecting flights as the testing could take up to a day.

What about face masks?

Masks intended to filter out airborne particles, such as N95 masks, have a limited effect, according to public health officials.

“It could be helpful if people who are sick wear masks,” said Tom Frieden, former director of the Centers for Disease Control and Prevention.

In Asia, wearing face masks is socially acceptable and common when people don’t feel well, he said. But their effectiveness also depends on the pathogen. For tuberculosis and measles, which are spread through very tiny droplets, face masks may not be helpful because the droplets can reach through the gauze or slip in around the mask.

For this coronavirus, “it might help,” Frieden said, assuming that the disease spreads through droplets in the air, which is something that officials do not know for sure.

“There is this concern, though,” he said. “If someone coughs on you, and you get a gob of virus on your mask, and then you take off your mask, put it on your finger, and then you touch your nose, you could get infected.”

Surgical masks are stronger, but they still have only a limited effect.

“As you breathe in and out, you’re breathing air from outside the face mask,” Mark Parrish, regional medical director of the medical and travel security firm International SOS, told the Telegraph. “So it will stop a little bit but not hugely.”

Surgical masks also need to be changed frequently and disposed of properly.

What happened with SARS and MERS?

In November 2002, the SARS epidemic began spreading through China: Over eight months, it moved to more than two dozen countries, killed 774 people, and infected more than 8,000 people. Health authorities say the “Patient Zero” came in contact with an animal in China’s Guangdong province, which borders Hong Kong.

The virus was contained in summer 2003. Health-care workers made up about 20% of victims in areas heavily hit with the disease, according to WHO. There’s still no cure for the disease, but the initial outbreak was contained by isolating suspected patients and screening passengers traveling from infected areas or those suspected of having symptoms.

One factor hindering initial efforts to contain the virus were the limits on coverage of the epidemic implemented by Chinese authorities.

MERS started spreading in the Middle East in 2012. Scientists say the first infection moved from a camel to human in Saudi Arabia. The disease is associated with the death of 790 people since 2012, the CDC reported in 2018. The outbreak was similarly contained by isolating patients. Health officials also warned against contact with camels and camel meat during the scare.