The authorities in Hong Kong, the United States, Thailand and Singapore have been screening visitors from Wuhan.
Coronaviruses are a broad family of viruses, but only six (the new one would make it seven) are known to infect people.
Illness symptoms related to the outbreak as said to include fever, cough, and difficulty breathing.
Passengers arriving at Los Angeles, San Francisco and JFK airport in New York City will have their temperatures taken and be asked about symptoms.
Chinese authorities have stepped up monitoring and disinfection efforts ahead of the lunar new year holiday in late January, when numerous country's 1.4 billion people will travel domestically and overseas.
As of Sunday, at least 170 people remained in Wuhan hospitals for centralized treatment, with 35 of them in serious condition and nine critically ill.
Viruses can change over time, adapting to new conditions and, in some cases, mutating in ways that change how they spread.
The Chinese government is keen to avoid a repeat of SARS, or severe acute respiratory syndrome, another coronavirus that started in southern China in late 2002 and spread to more than two dozen countries, killing almost 800 people.
The authorities did not explicitly state whether this was a case of human-to-human transmission.
Medical staff members carry a patient into the Jinyintan hospital, where patients infected by a mysterious virus are being treated, in Wuhan in China's central Hubei province on January 18, 2020. There have also been reports of people infected with coronavirus outside of China who had recently traveled to Wuhan.
"Entry screening alone is not a guarantee against the possible importation of this new virus but is an important public health tool during periods of uncertainty and part of a multilayered government response strategy", said the statement.
One estimate Friday by the MRC Centre for Global Infectious Disease Analysis at Imperial College London suggested that there could be as many as 1,700 cases.
Shenzhen is China's fourth-largest city, with a population of about 12.5 million and is about 550 air miles from Wuhan.
News about the outbreak was trending on Weibo, a microblogging platform in China, on Sunday morning. "We're about to celebrate the New Year, hope everyone is safe".