A staffer in the office of US Vice President Mike Pence, the pointman for Washington's response to the coronavirus outbreak, has tested positive for the illness, a spokeswoman said Friday.

"Neither President Trump nor Vice President Pence had close contact with the individual. Further contact tracing is being conducted," Pence's press secretary Katie Miller said.

Pence has appeared at Trump's side at the daily White House press conferences to announce developments in the US fight against the outbreak.

It was the latest case of COVID-19 to brush the inner circle of US leadership. 

An attendee at a political conference last month featuring Trump and Pence tested positive for the illness, and multiple political figures who regularly meet with the president and vice president have gone into preventive self-quarantine.

Trump tested negative for the novel coronavirus last week. He agreed to the test after coming in contact with several members of a Brazilian presidential delegation visiting his Florida resort who have since been found to have the virus.

The news came as COVID-19-linked deaths in the US rose to 216 -- more than doubling in three days -- with more than 16,600 confirmed infections, according to a tally by Johns Hopkins University.

On Friday, New York and Illinois followed California in locking down to stem the coronavirus pandemic, effectively sealing off America's largest cities of New York, Los Angeles and Chicago.