ESR / Supplied
Sewage samples taken in Nelson on November 29 tested positive for the presence of Covid-19 (file photo).
Covid wastewater testing in Nelson-Tasman has been increased following the discovery of active cases in the community.
On Monday, the first case of Covid-19 in the region since 2020 was confirmed, with the number rising to 14 on Friday.
Until the week ending November 27 (last Saturday), wastewater testing for Covid-19 conducted by the Institute of Environmental Science and Research had detected no trace of the virus in Nelson, Richmond and Motueka.
However, ESR senior scientist Dr Brent Gilpin said the results of a sample of Nelson’s sewage collected on November 29 – the same day the first case was announced – detected the virus. . A test in Richmond on November 30 came back negative.
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Dr Gilpin said testing has been increased across the region, to three drives from Nelson and up to two a week from Richmond and Motueka.
He said other samples collected in Nelson and Motueka are currently being processed, with results expected later on Friday.
Dr Gilpin said that while the presence of Covid-19 in Nelson’s sewage was an expected result, a positive sample did not always equate to active infections in the community – just as a negative sample did not necessarily mean that the virus was absent.
âA positive detection in wastewater indicates that at least one person has released SARS-CoV-2 in wastewater in the 24 hours before each sample was taken.
âA positive detection in wastewater could also be due to a case in a managed isolation facility and / or a historical non-infectious case, or a recently recovered non-infectious case that is still excreting [the virus at] low levels. “
Dr Gilpin said if there were any positive cases in the community, sewage monitoring would detect them, except for people who were not connected to the cross-linked sewage systems.
Additional factors affecting the tests included the level of infection, vaccination status, treatment and frequency of bowel movements, he said.
âWe would certainly encourage anyone showing symptoms or having been in contact with people outside the area to follow health advice and get tested.
“In the meantime, to offer the best chance of limiting the spread, it is best that everyone in the city treat everyone as potentially infected and take appropriate precautions.”