(CNN) The State Department announced a highest-level warning on Thursday not to travel to China due to the recent coronavirus outbreak.

"Do not travel to China due to novel coronavirus first identified in Wuhan, China," the Level 4 alert states, noting that the World Health Organization declared the coronavirus a public health emergency of international concern earlier that day.

"Travelers should be prepared for travel restrictions to be put into effect with little or no advance notice. Commercial carriers have reduced or suspended routes to and from China," the alert notes stated. "Those currently in China should consider departing using commercial means."

The news comes after the US Centers for Disease Control and Prevention announced on Thursday that the husband of an Illinois woman with Wuhan coronavirus is now infected with the illness -- the first confirmed case of person-to-person transmission in the United States.

The number of cases of the virus, which has killed at least 213 people , shot up to more than 8,100 in mainland China alone by Thursday evening. While the virus originated in the Chinese city of Wuhan in December, there are now more than 100 cases in 20 other countries and territories spanning Asia, North America, Europe and the Middle East. India and the Philippines were the latest countries to confirm the virus had reached their shores.

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