Scientists are increasingly concerned about a new virus that is spreading in Asia . The virus, which causes a respiratory illness, emerged in the Chinese city of Wuhan in December and has infected some 300 people and killed at least 6. Thailand, Japan and South Korea are among the other nations that have also reported infections.

Researchers have identified the pathogen as a coronavirus , from the family that causes severe acute respiratory syndrome, or SARS, which killed hundreds of people in 2002 and 2003. Chinese officials have also confirmed that the virus can spread from person to person.

Follow the latest news on the Wuhan virus here.

21 January 19:45

The United States has confirmed its first case of the new coronavirus, the US Centers for Disease Control and Prevention (CDC) said on 21 January. A 30-year-old man in Washington state has been diagnosed with the illness after a recent trip to China, making the United States the fifth country to report the disease — and the first outside of Asia to do so.

The man had been admitted to a hospital in Everett, Washington, last week with pneumonia but “is right now, very healthy”, Nancy Messonnier, the director of the CDC's National Centre for Immunization and Respiratory Diseases, told reporters. He is under observation at the hospital.

The CDC says that the man did not have symptoms upon arrival in Seattle, Washington, but developed a fever on 16 January and sought treatment. A hospital in Washington state collected blood from the man and shipped it to the CDC, which identified the virus in the samples on 20 January. The CDC is now identifying individuals who had contact with the man.

International airports in New York City, Los Angeles and San Francisco, California, have been screening arriving passengers for signs of coronavirus infection since 17 January. All three facilities receive direct flights from Wuhan. The CDC says it will now expand the screening to airports in Atlanta, Georgia, and Chicago, Illinois. All travelers leaving Wuhan for the United States will be re-routed into one of the five airports with screening programmes.

21 January Infections have been confirmed in 15 health-care workers in Wuhan ; scientists say this suggests that the virus is more adept at human-to-human transmission than was first thought. Previously, Chinese authorities and the World Health Organization had said that there had been some limited cases of human-to-human transmission between family members, but that animals seemed to be the most likely source of the virus.

In response to the worsening outbreak, the World Health Organization has called a meeting on 22 January to decide whether to declare a public-health emergency.