Queensland Health is investigating after traces of coronavirus were found in Townsville’s sewage, as the state records one new case in the past 24 hours.

Health Minister Steven Miles said the man in his 20s had recently returned from the Philippines, and tested positive on day 10 of hotel quarantine.

It comes as authorities try to determine how the virus was detected in Townsville’s wastewater.

“We will be working with the Townsville Hospital and Health Service to just increase our testing rate there,” Mr Miles said.

“[We will] try to work out if there is a case or cases in or around Townsville that we are unaware of, and that have been picked up in that wastewater testing.

“It underlines just how valuable that wastewater testing is proving to be.”

The state’s chief health officer Jeannette Young had several theories about what could be behind the wastewater result in Townsville, including an undetected case in the north Queensland city.

“We do know that twenty per cent of people can shed the virus and have absolutely no symptoms,” she said.

“So that could have occurred and they could have spread it to someone — so that is my concern.

“I hope that theory is wrong.

“There could have been ships offshore that could have released sewage.

“My other theory is that someone has travelled through Townsville, whether it be a freight worker, whether it be someone else … could even be someone who was in quarantine, had it, has recovered and now has gone to Townsville.

“We know you can shed virus for quite sometime after you’ve recovered.”

Dr Young has also been notified of a positive wastewater test result in Goodna, west of Brisbane, but said it was likely linked to previously known cases.

“But there may be something we don’t know about, so please, if you live in Goodna and you have got any symptoms, please come forward and get tested,” she said.

“We’re not seeing other respiratory viruses out there, we have seen hardly any flu — so if you’ve got symptoms, there’s every chance it could be COVID.”

–ABC