Authorities in Texas are investigating a second suspected case on US soil of a deadly Chinese virus, namely a college student who had recently returned from the city at the heart of the outbreak, officials said Thursday.

Brazos County, just northwest of Houston, "is investigating a suspected case of the 2019 Novel Coronavirus (2019-nCoV)," its health authority wrote in a statement on Facebook.

"The patient traveled from Wuhan, China, where the coronavirus originated," it added.

The patient's age is somewhere between 20 and 30 and they returned to the United States, where they are attending Texas A&M University, days before health screenings began at airports on January 15, local health official Eric Wilke told reporters.

"The person presented to an area emergency department yesterday mostly out of concern, not out of symptoms," said Wilke, adding that they were now being kept isolated at home while testing was performed, with the result likely to arrive over the next day or two.

The patient had "mild upper respiratory symptoms" including cough and congestion and appeared to be improving. Such symptoms are common in the middle of winter flu season, but the patient was being screened further on the basis of their travel history.

A blood sample has been sent to the headquarters of the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, which should arrive late Thursday or early Friday, with a result expected within 24 hours after that.

If the case is confirmed, the patient would be the second person to be infected with the pathogen on US soil after a man in his 30s near Seattle reported himself to authorities on January 19.

That man, a US resident who also recently traveled to Wuhan, is said to be recovering well and is due to be released from hospital soon.

CDC officials had already warned that there would be more cases in the US given the frequency of international travel.

All air traffic from Wuhan is currently being funnelled through five airports where health officials have been deployed to carry out screening with questionnaires and temperature checks.

The new respiratory virus has claimed 18 lives since emerging from a seafood and animal market in Wuhan and infected hundreds more.

China has locked down some 20 million people at the epicenter of the outbreak, but the World Health Organization said Thursday the disease did not yet constitute a global health emergency.

But it has generated alarm because of its similarity to SARS (Severe Acute Respiratory Syndrome), which killed nearly 650 people across mainland China and Hong Kong in 2002-2003.

© Agence France-Presse