Day 11 of zero community transmission of coronavirus across NSW

The news comes as state borders start to reopen to some residents and procedures are streamlined to encourage more COVID-safe outdoor dining in NSW.

Eleven coronavirus cases were recorded in overseas travellers in hotel quarantine overnight, bringing the total number of cases in NSW to 4,057.

Testing numbers remain low as there were just 5,385 tests reported in the 24-hour reporting period.

"Testing numbers have dropped recently, which is a concern," a NSW Health statement said.

"Come forward for testing right away if you have even the mildest of symptoms like a runny nose or scratchy throat, cough, fever or other symptoms that could be COVID-19."

People in the Hawkesbury and South Western Sydney are also on alert after the state's sewage surveillance program detected fragments of the virus at the North Richmond and West Camden treatment plants.

The most recent cases in the West Camden catchment were reported in September, but no one living in the North Richmond catchment has recently tested positive for COVID-19.

Virus fragments in sewage can mean that there are active cases in the catchment area, but people can continue to 'shed' virus genetic material for some weeks after recovery.

NSW Health is treating 50 COVID-19 cases, including three in intensive care, none of whom are being ventilated. Eighty per cent of cases being treated by NSW Health are in non-acute, out-of-hospital care.