FRAGMENTS of COVID-19 have been detected in the sewage system of about 200,000 people in Newcastle and Lake Macquarie, raising concerns that cases may have been missed.
The Hunter has recorded no new cases of COVID-19 since Thursday. But a recent sample taken from the Burwood Beach sewage treatment plant has found traces of COVID-19, indicating someone who has been infected is "shedding" the virus, Hunter New England Health says.
"It's quite a surprise for us to actually detect the virus in the sewage at this time with only a small number of cases in the community," public health physician Dr David Durrheim said. "We may have missed cases. So it is critical that we test more."
With studies from Italy and Iceland showing between 50 to 75 per cent of positive COVID cases were asymptomatic, HMRI researcher and respiratory clinician, Professor Peter Wark, said it was becoming clear that a large proportion of people could have "very mild" illness or no symptoms at all.
He said it comes as mounting evidence showed COVID-19 may leave a "long-lasting impression" on its victims, and not just the most severely affected or the elderly and frail.
"We are starting to appreciate that clotting disorders are over-represented in people who have COVID-19," Professor Wark said. "There are complications like pulmonary embolism, stroke, and possibly heart disease or heart attacks in severe cases."
The Burwood Beach sewage treatment plant is a wastewater catchment for Newcastle, Dudley, Charlestown, Jesmond, Mayfield and Carrington. The sample was taken as part of a NSW Health research program to support the public health response to the pandemic, as infected people's stools may contain viral fragments.
Shedding could extend for "several weeks" after the person's infectious period.
"With recent cases of COVID-19 identified in this wastewater catchment, which includes the Newcastle city area and surrounding suburbs of Dudley, Charlestown, Jesmond, Mayfield and Carrington, it's really important that anyone with symptoms in these communities gets tested," Dr Durrheim said.
"Anyone with the mildest respiratory symptoms - a cold or flu-like scratchy throat, runny nose, or a cough, really must be tested.
"And please isolate at home until you get a negative result. Don't take the virus out into the community.
"We need to all work together to give the virus no further chance of spreading in Newcastle and surrounding areas."
Professor Wark said there was a "large group" of people who had tested positive for COVID-19 suffering persistent symptoms after their illness; in some cases, more than 60 days after infection.
"We don't quite know how many, but they are not insubstantial," he said.
"These 'long-haulers' describe symptoms of fatigue, tiredness, and persistence of symptoms like breathlessness, aches and pains in the muscles, and aches and pains in the joints.
He said anyone with a severe disease would be expected to suffer long-lasting consequences, but COVID-19 seemed to have persistent symptoms even in those with milder forms of the illness.
The size and the seriousness of the problem was still unknown.
"It's possible this could represent an immune response to the presence of the virus. But we learning as we go," he said. "It is very new. We have had a bit more time for most illnesses, even influenza - and while that can change from year to year, we are having to cope with what is a very novel virus with very novel aspects to it as well. And it brings us to these long term complications that are starting to emerge.
"The best way not to get long term symptoms of COVID-19 would be to not get it in the first place - so, if everybody can pay attention to the messaging and minimise social contacts, that would be fantastic."
Dr Durrheim said people did not need to be "nervous" about drinking tap water and swimming at the beach.
"Drinking water is treated before being delivered to your tap and remains safe to drink," he said.
"The virus is killed by usual sewage treatment processes before it is discharged to the environment. The wastewater treatment process is designed to [kill] or remove even the toughest microorganisms, including viruses, bacteria and protozoa."
Further testing will be undertaken as the NSW Health research program continues.