Washington, May 16 (IANS): COVID-19 may have occurred in the US before mid-January as two persons with positive serology or blood-based tests had coronavirus-like illness last December, a Washington-based health official said.

Among 295 probable cases, 35 had positive serological or blood tests and two of those individuals reported having a COVID-like illness in mid- to late December 2019, Chris Spitters, the Snohomish district's health officer, said on Friday.

These two persons told their district's case investigators they got sick with COVID-like illnesses in mid- to late December, several weeks prior to the country's first confirmed case in mid-January, reports Xinhua news agency.

"Given reports like the ones that we've had and others around the country, the introduction of COVID-19 may have occurred prior to mid-January," Spitters said.

"A positive serology test indicates prior coronavirus infection. It does not provide details on when the infection was acquired," he added.

Spitters noted that respiratory-tract symptoms experienced in December in each case overlap with other illnesses.

"It is hard to determine if their illness in December truly was COVID-19, or if it was due to another respiratory infection and they later acquired an asymptomatic COVID-19 infection."

An additional 20 to 30 positive serologic results have been reported to the health district and were awaiting a probe.

Health district investigators will follow up on reports of positive serologic results as time is available, Spitters said.

The development comes as the US currently accounts for the world's highest number of COVID-19 cases and deaths at 1,442,819 and 87,530, respectively.