In a statement on Friday, the Mecklenburg County Public Health authorities said that the four people were two prospective attendees and two support staff, reports Xinhua news agency.

"These individuals were immediately issued isolation instructions and any known close contacts were notified and issued quarantine instructions by Mecklenburg County Public Health," the statement said, adding that approximately 792 tests were conducted among individuals attending or providing support to the RNC event in Charlotte that ran from Monday to Thursday.

Mecklenburg County health officials had raised concerns over the lack of mask wearing and social distancing at the scaled-back event, where more than 300 delegates gathered in person to formally renominate President Donald Trump and Vice President Mike Pence for a second term in office.

Trump and Pence travelled to Charlotte on Monday to address the delegates, who were instructed to wear masks and practice social distancing, but videos of the event showed few people follow the guidance.

Nearly 25,000 residents in Mecklenburg County, whose largest city is Charlotte, have contracted the coronavirus.

Most of the RNC events were held virtually but Trump's acceptance speech from the White House South Lawn on Thursday night was delivered to a crowd of more than 1,000 people, most of whom were not wearing masks.