Mystery surrounds positive sewage tests for COVID-19 in areas which haven’t seen a case in months

Townsville, Nambour and Rockhampton are the latest towns to detect the virus in sewage but Queensland Health cannot explain why some areas show traces yet have no documented infections. SEE FULL LIST

Traces of the COVID-19 virus have been detected in more than 40 sewage samples in Queensland since wastewater analysis began last July, some of them mysteriously found in areas that have gone months without a confirmed case.

The latest positive results were recorded today in samples collected earlier this month at Townsville, Nambour and Rockhampton, prompting Chief Health Officer Jeannette Young to urge people living in those communities to be “vigilant” about signs of the virus.

Wastewater testing for the pandemic virus began as a pilot project in Queensland last July but has since become part of the state’s COVID-19 surveillance program.

The highly sensitive tests, which pick up genetic fragments of SARS-CoV-2, the virus that causes COVID-19, alerts Dr Young to the possibility of undetected infections in the community.

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Queensland Chief Health Officer, Dr Jeannette Young. Photo: Mark Cranitch.

It can help identify towns or cities Queensland Health can target for testing, particularly where no cases have been detected for months.

Positive Queensland sewage results have been received from as far north as Cairns to as far south as Stanthorpe.

The tourism hot spots of Bargara and Hervey Bay, in the Wide Bay region, and Airlie Beach in the Whitsundays, are among places where evidence of the virus has been found in sewage.

But the wastewater analysis is not powerful enough to be able to discern whether a community has undetected active cases of SARS-CoV-2, or if a person who has been diagnosed with COVID-19, but is no longer infectious, continues to shed the virus.

How many mystery infections the wastewater fragments relate to – in other words, unidentified COVID-19 cases – will never be known.

The case earlier this month of a Cairns man, in his 40s, who tested negative in hotel quarantine after returning to Australia from the Congo in September, would likely never have been picked up if he was not required to undergo a COVID-19 test as a condition of returning to work.

Dr Young has speculated the man – whose COVID-19 case is considered “historic”, meaning he no longer has active disease – may be responsible for viral fragments of SARS-CoV-2 continuing to be found in North Cairns sewage.

“We know you can shed for up to nine months when you’re positive,” she said.

Aerial view of the wastewater treatment plant at Hervey Bay's Pulgul Creek.

Since October 5, data supplied to The Sunday Mail shows Queensland recorded 124 cases of the pandemic virus that were acquired overseas and detected in hotel quarantine.

Once these cases are deemed to be no longer infectious and are allowed to return home, they can travel anywhere in the state, and may continue to excrete viral particles, for weeks, maybe months, including while on holidays.

The COVID-19 sewage testing project is a joint initiative between Queensland Health, the University of Queensland and CSIRO.

Sewage samples are being collected from about 40 locations in Queensland.

Dr Young urged people living in Townsville, Nambour and Rockhampton, where the latest positive wastewater results have been recorded, to get tested if they develop even mild symptoms of the virus.

“If there is a case in the community, it is critical we detect it through our testing mechanisms as quickly as possible to contain any potential spread and protect the great progress Queensland has made in recent months,” she said.

“I also want to reassure the community, local drinking water is thoroughly treated through processes that are designed to remove or kill microorganisms before they reach your taps.”

Queensland recorded no new cases of SARS-CoV-2 in the past 24 hours. The state has had 1303 confirmed cases of the virus since the first one in late January last year.

Of those, 21 are still considered active.

Positive wastewater testing results for the COVID-19 virus in Queensland

January 23, 2021: Rockhampton, Townsville and Nambour.

January 22: Mackay South, Goodna, Wacol, Carole Park.

January 19: Merrimac (Gold Coast), Cairns North, Cannonvale (Airlie Beach area).

January 15: Gibson Island (South Brisbane), Luggage Point (North Brisbane), Pimpama, Coombabah (Gold Coast), Capalaba, Loganholme, Wynnum.

January 9: Redcliffe.

January 8: Gibson Island (South Brisbane), Cleveland Bay (Townsville), Pulgul (Hervey Bay), Maryborough.

January 5: Warwick, Stanthorpe, Loganholme, Cairns.

January 1: Recent positive wastewater testing results announced in Bundamba, Merrimac (Gold Coast), Wynnum, Bundaberg, Bargara, Victoria Point, Oxley Creek, Goodna, Fairfield, Cairns North, Redcliffe and Nambour.

November 27, 2020: Traces of SARS-CoV-2, the virus that causes COVID-19, are found at both the Cairns North and Cairns South wastewater treatment plants. It’s the second week in a row Cairns North has recorded a positive reading.

October 10: Chief Health Officer Jeannette Young announces traces of SARS-CoV-2 have been found in Goodna and Townsville sewage. Regarding the positive Townsville results, she suggests ships offshore with a positive COVID-19 case, may have released sewage.

October 28: Carole Park.

September 18: Follow-up testing returns negative after earlier results showing low-level viral fragments at Pulgul in Hervey Bay.

September 3: Viral fragments detected at the Cannonvale-Airlie Beach sewage treatment plant.

July: Pilot sewage program testing for SARS-CoV-2 begins mid-July

For the latest COVID-19 sewage results: health.qld.gov.au