The newly identified coronavirus that emerged in the central Chinese city of Wuhan has been declared an international health emergency, and the effort to contain it also spans the globe. The Chinese government has implemented the most ambitious quarantine in modern times, as health care workers knock on doors in search of infected people and travelers in airports across the world are scanned for signs of fever. The effort is complicated by the virus’s incubation period of up to two weeks -- a time when the infected person may have no symptoms but still be contagious -- as well as the challenge of identifying those with such mild cases they don’t realize they are ill. Here’s a breakdown of the work to rein in what’s been dubbed 2019-nCoV, for 2019 novel coronavirus:

Monitoring

Within China: Officials said they would track down people who left Wuhan, a city of 11 million, before the quarantine was imposed, as many migrant workers headed back to the countryside to celebrate the Lunar New Year with their families. Officials said they would be registered, visited frequently by medical personnel and taken for treatment if symptoms developed. Xinhua reported that health officials in Beijing asked those returning to Wuhan from anywhere to stay at home for two weeks, record their temperature and seek treatment if they develop a cough or fever. But a shortage of testing kits and overworked hospital staff are straining the health care system, hampering efforts to accurately track how many people have the pathogen. And there’s evidence that people may be contagious even when asymptomatic.

Elsewhere: Airports globally and border crossings with China have implemented monitoring systems including thermal scanners and questionnaires in an effort to catch cases early. In the U.S., the Centers for Disease Control and Prevention said it would funnel all air traffic from China through certain airports, where passengers would be screened for fevers or other symptoms. The drawback to this approach, however, is that it may miss people coming into the U.S. from places other than China who might have been infected by asymptomatic patients during the journey. The passengers are given cards with details about what to watch for. Social media and traditional news outlets have also spread the word. The first two patients identified in the U.S. sought medical attention on their own accord because they were concerned that they might be infected, showing that awareness levels are high.

Contact tracing

When a new case is identified, the patient is put in isolation, often in a hospital, to prevent him or her from spreading the germs. A medical worker takes a thorough history, trying to identify every person who has been within 6 feet (2 meters) of the patient since symptoms emerged. According to the WHO, Chinese authorities place close contacts (family members and others living in the patient’s home, co-workers, possible care-givers and others) under medical observation, which may include isolation at home with regular temperature checks. If there are no symptoms after 14 days, the contacts are released, the WHO said. Other potential contacts could be neighbors, fellow passengers on public transportation, people who attended the same social events, shopped or visited doctors at the same time. Breaking the chain of transmission is what officials believe will ultimately curtail the outbreak and prevent a pandemic, which is an epidemic of global proportions.

Isolation

Isolation is a tricky issue because it’s unclear how well it works or if it’s been put in place quickly enough. The most critical time for isolation is when an infected person sheds the virus, essentially putting it out into the world. Scientists believe the virus is spread primarily through droplets that could be emitted by an infected person’s cough and transferred to their hands or surfaces and objects. There’s a theoretical risk that it could spread through fine aerosol particles and feces. Chinese authorities have said it’s possible people who are still incubating the virus and show no symptoms may spread it. One such case emerged in Germany linked to a company training event that was attended by an employee visiting from China who had no symptoms of disease during her stay. There have been cases reported where the virus has spread along a four-person chain, indicating that it’s more transmissible than earlier thought. Some of the most vulnerable people are the health care workers caring for seriously ill patients; 15 cases occurred among workers at a single hospital in Wuhan.

Travel restrictions

Hong Kong, the international financial center that functions with some autonomy from China, announced travel restrictions from the mainland. Singapore, the Philippines and New Zealand banned visitors from China, while South Korea, Iraq, Italy and Indonesia announced travel restrictions. Airlines reduced scheduled flights to and from China in preparation for lengthy shutdowns of service, with Delta, United and American Airlines following the lead of British Airways, Air France and Deutsche Lufthansa AG. United and American said they would not resume until late March, and Delta not until April. The U.S. State Department warned U.S. citizens against travel to China and said it was helping Americans in Wuhan get out of China. The U.S. declared a public health emergency and said that starting Feb. 2 it would bar entry to most foreign nationals who have been in China within two weeks of their arrival to the U.S.

Quarantines

Inside China: the government has imposed a quarantine on Wuhan and more than a dozen other cities in the region, a travel ban covering in excess of 50 million people. The move came ahead of the Lunar New Year holiday period, when an estimated 3 billion trips are made, about 15 million in Wuhan alone. The mayor estimated about 5 million residents left before the Jan. 23 lockdown, according to media reports. Wenzhou, a port city of 9 million people, became the first city outside central Hubei province to impose quarantine measures, telling families that only one person will be allowed out of the house every two days to shop for necessities. Wenzhou is in Zhejiang province, which had the highest number of confirmed cases outside Hubei.

Elsewhere: The CDC said that it was putting 195 Americans who had been repatriated from the outbreak’s center under federal quarantine at an Air Force base in California, the first such effort since the 1960s. All Americans who had been in Hubei province during the two weeks before their arrival would also be subject to quarantine. Citizens returning from elsewhere in China will be subject to screening, and are being asked to stay at home for two weeks while being monitored. Some health officials warned that in modern times, quarantines have yielded limited results. Toronto’s use of quarantine wasn’t effective in slowing the SARS epidemic of 2002-2004 there, Richard Schabas, a former public-health physician who was Ontario’s chief medical officer from 1987 to 1997, concluded in a study in 2004. An impoverished neighborhood in Liberia quarantined during an Ebola outbreak in 2014 responded with violent riots.

Testing

China sequenced the virus’s genome within days of detecting the outbreak and on Jan. 10 posted the information to public databases widely used by researchers. That contrasts with the months of delay seen with its response to the 2002 outbreak of SARS. Speedy access to the new virus’s genetic fingerprint allowed health officials in Japan and Thailand to quickly confirm cases that had been exported from China, followed by the U.S., France and other countries. Still, the process isn’t easy. Medical staff must take swabs from the nose and throat of potentially infected patients, along with blood samples, and send them to laboratories that are equipped to do genetic sequencing. While the work can take four to six hours, shipping the swabs to the laboratory can take much longer. Chinese health officials approved two new kits on Jan. 28, in addition to the existing four types, according to Xinhua News Agency. One of the new kits can give results in about 30 minutes, according to Technology Daily. In the U.S., the only facility currently conducting the work is at the CDC in Atlanta. Researchers are working to develop a faster process that can be done closer to the patient’s bedside.

Vaccines and Drug Therapies

Antiviral drugs that have shown signs of helping control other types of coronaviruses, such as remdesivir and lopinavir/ritonavir, are being examined to see if they offer any help for those infected with 2019-nCoV. Pharmaceutical companies including Moderna Inc. and Novavax Inc. say they have begun work on a potential vaccine. Health officials say a version might be available for the first stages of human testing in as little as three months. But developing an effective vaccine generally takes years.

--With assistance from Jason Gale.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

To contact the editors responsible for this story: Sharon Chen at schen462@bloomberg.net, John O’Neil, Paul Geitner

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