HEALTH officials are holding their breath as they wait to find out whether COVID-19 fragments found in a NSW Hunter region sewage catchment indicate undetected community spread of the virus.
Newcastle and Lake Macquarie COVID-19 testing centres were "hammered" by people with cold and flu-like symptoms on Monday following the news fragments of the virus had been detected in the Burwood Beach Wastewater Treatment Works - the catchment for Newcastle, Dudley, Charlestown, Jesmond, Mayfield and Carrington.
Hunter public health physician Dr David Durrheim said a confirmed case - a returned traveller who had been diagnosed and managed in hotel quarantine in Sydney - had returned to the area in recent days. But the sewage surveillance system would have to be "unbelievably sensitive" if it picked up just one case shedding the virus in a catchment area of 225,000 people.
"We generally believe we can detect one person shedding the virus particles in about 30,000 people contributing to a particular sewage catchment," he said.
"When we had a detect at Burwood Beach in August last year, there were up to six people we knew of in that catchment who would have probably been shedding viral fragments. If the overseas returning traveler is the reason for this detect, it has potentially detected one-in-225,000 - which would make this an unbelievably sensitive surveillance. The other side is that potentially there is undetected, low-level community transmission in that catchment area."
Dr Durrheim said lab testing for COVID-19 had been at an "all time low", meaning they could not be confident it would have been picked up.
The results of additional sewage testing from samples collected on Monday would be back mid-week.
"If we get a couple of non-detects I will be breathing a lot easier," he said.
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Dr Durrheim said staff at the region's COVID-19 testing clinics were working "flat out" on Monday after weeks of little demand.
"After quite a pause where staff were sitting around wondering why they were even at the testing centres, now they are working extremely hard and my understanding is that every testing centre in Lake Macquarie and Newcastle is working flat out to cover the demand," he said.
It would not be known until Tuesday how many people presented for testing on Monday, but data from the past three weeks showed testing numbers were between 1200 and 1500 a week in Newcastle.
"For the moment we need to hold our breath."
Dr Durrheim said we had probably become a little bit complacent.
"Things have returned to normal and we're getting big gatherings together, and with that we have lost some of the good habits we developed during COVID-19, like keeping 1.5 metres and avoiding handshaking," he said.
"We probably are more vulnerable now to spread in the community than we have been for months."
He said the sewage detection could not plausibly be linked to the recent World Surf League event in Newcastle.
"We would have picked that up two weeks ago, rather than now," he said.
"We worked very closely with the World Surfing League. All the overseas participants and support staff completed quarantine in Sydney, and all were swabbed at least three times.
"One competitor was swabbed multiples times because she'd had a historical infection - so we can be pretty sure no one was infectious, and they had all moved on to the next event."
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