Testing of wastewater in Townsville has turned up traces of Covid-19 for the first time in what authorities say is a worrying development.
One new case has also been reported in a man in his 20s who recently returned from the Philippines and tested positive on day 10 in quarantine in Brisbane.
Deputy Premier Steven Miles said the positive result from sewage in Townsville was the first such result in the regional centre.
"We will be working with the Townsville Hospital and health service to increase testing rates and to try to work out if there is a case or cases in and around Townsville that have been picked up in that wastewater testing," he said on Saturday.
"It underlines just how valuable that wastewater testing is proving to be."
Chief Health Officer Jeannette Young said she was worried by the result considering Townsville had not reported a Covid-19 case for many weeks.
"This is in Townsville where we know we haven't had cases in quite some time," she said.
Dr Young urged everyone in Townsville to get tested if they felt unwell to give authorities the best chance of identifying the first case if any cluster emerged.
She said it was possible that the positive result had come from someone who had previously had Covid-19 and recovered but was still shedding inactive virus, or someone with an old infection who had passed through the town.
"Someone who has travelled through Townsville, a freight worker. It could even be someone who has been in quarantine," Dr Young said.
"But my first theory, which I hope is incorrect, is it is someone who has active Covid-19 in Townsville.
"That's why I would like anyone in Townsville today who has any symptoms to come forward and get tested."
Mr Miles also hit back at Queensland's approach to providing exemptions to hotel quarantine requirements, saying he had full faith that all such exemptions were being handled properly by medical officials.
He said all exemptions were based entirely on health considerations.
"I'm a bit sick and tired of people trying to use individual stories, the individual distress of people, to try to criticise the restrictions that have kept Queenslanders safe, he said.
"We're not going to be bullied by these campaigns. We're going to stick to our guns, we're going to stay strong and we're going to keep Queenslanders safe."
Dr Young said all applications were subject to a very thorough process with about 60 such exemptions granted so far.
"We do have a process to exempt people from hotel quarantine," she said.
"That decision is made purely on the health needs of the individual."
The single new coronavirus case in Queensland on Saturday took the state's total since the start of the pandemic to 1161 with more than 850 acquired overseas.
Three people are in hospital, among the four infections still considered active.
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