Washington state health officials said Wednesday that investigators have identified 16 “close contacts” of a 30-year-old man who is the first confirmed case of coronavirus diagnosed in the United States.

The Snohomish County resident, who has not been named, identified people that he has interacted with since returning from Wuhan. Those named will be actively monitored for signs of any illness by local health officials.

Health officials said that they consider a “close contact” to be anyone who is within 6 feet of an infected person, like having a meal or meetings together, but that they are not asking those contacts to isolate themselves unless they have symptoms.

Health staff will reach out to the contacts daily to see if they have a fever or cough and to check if they develop any symptoms. Dr. Chris Spitters, the health officer for the Snohomish Health District, said there is also a call center set up to take resident’s questions about the virus.