The Centers for Disease Control and Prevention on Thursday escalated its health warning to a level 3 as the coronavirus continues to spread, recommending that people avoid all nonessential travel to Wuhan, China.

The State Department reiterated its level 2 travel advisory, which urges people to exercise caution if traveling to an affected area.

An initial State Department website post erroneously showed that it had raised its travel advisory to a level 3, but the department later said in a statement to CNBC that it had made a mistake and that the travel advisory remains at a level 2.

"Today, we updated the China Travel Advisory to include additional information on the outbreak. The Advisory remains a Level 2: Exercise Increased Caution," a State Department spokesperson told CNBC. "Earlier today, the Travel.State.gov briefly displayed an inaccurate version of the Advisory due to a technical error – we apologize for any confusion. Again, the Advisory level has not changed."

The total number of coronavirus cases in China rose to 634 on Thursday as local authorities quarantined at least two major cities and canceled Lunar New Year's events in Beijing, China state television reported.

Chinese authorities have suspended air and train travel in Wuhan, which is under quarantine.

The virus — which was first diagnosed less than a month ago — has already killed at least 17 people in China and infected roughly 650 people around the world, including firsts in Singapore and Saudi Arabia, according to multiple reports from international and local media. Medical teams have been dispatched to affected cities, and hospitals are asking for donations of essential items including face masks, eye protectors, protective uniforms and sanitizer.