NSW health authorities have recorded just one coronavirus infection in the 24 hours to 8pm Thursday.

It is the lowest number of new cases since July 2, when there were no new infections reported and on August 18, when there were three.

The new case is a close contact of a previously reported case at Hornsby Hospital.

“The case went into isolation before the commencement of their infectious period following notification of the previous Hornsby case,” state chief health officer Kerry Chant said.

“While case numbers have remained low this week the virus continues to circulate in the community and vigilance must be maintained.

“It is vital that high rates of testing continue in order to find the source of the cases still under investigation and to identify and stop further spread of the virus.”

Friday was also the first time since August 7 where an unknown source didn’t factor into daily infection figures.

An epidemiological report released by NSW Health examining the week ending on August 15 said investigations were unable to link seven infections to known cases or clusters.

NSW Premier Gladys Berejiklian expressed several times in the past fortnight about her “anxiety” over cases with unknown sources.

She said these mystery infections were appearing predominantly in Sydney’s west and south-west.

There were 32,580 COVID-19 tests were conducted on Thursday, up from 28,767 tests from the day before.