US health officials on Thursday reported the first case of person-to-person spread of the novel coronavirus in the United States.

The infected individual is married to the Chicago woman who got sick from the virus after she returned from a trip to Wuhan, China, the epicentre of the outbreak. There have been cases reported of the infectious virus spreading to others in a household or workplace in China and elsewhere.

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The new case is the sixth reported in the US. The other five were travellers who developed the illness after returning to the US from China. The latest patient had not been in China.

The Chicago woman, who is in her 60s, returned from central China on January 13, then last week went to a hospital with symptoms and was diagnosed with the viral illness. She and her husband are hospitalised.

Experts have said they expected additional cases, and that at least some limited spread of the disease in the US was likely. Health officials think the new virus spreads mainly from droplets when an infected person coughs or sneezes, similar to how the flu spreads.

The Centers for Disease Control and Prevention (CDC) and Illinois health officials announced the case Thursday.

At a news briefing last Friday, the CDC's Dr Nancy Messonnier said: "We are likely going to see some cases among close contacts of travellers and human-to-human transmission."

The virus can cause fever, coughing, wheezing and pneumonia. It is a member of the coronavirus family that's a close cousin to the SARS and MERS viruses that have caused outbreaks in the past. The new virus has sickened thousands, mostly in China, and killed about 170.

An international outbreak caused by the virus first emerged last month in China. Doctors there began seeing the new virus in people who got sick after spending time at a wholesale food market in Wuhan. Officials said the virus probably initially spread from animals to people, as did SARS and MERS.