ABSTRACT Map of the North Island of New Zealand showing locations of Auckland and Palmerston North with text describing detection of SARS-CoV-2 in Palmerston North sewage on three consecutive days in 35 million litres of wastewater due to a single COVID case travelling from Auckland to Palmerston North. This study demonstrates the sensitivity of wastewater-based epidemiology for the detection of viruses such as SARS-CoV-2. New Zealand achieved nationwide sustained elimination of COVID-19 in May 2020. In August 2021, community transmission of SARS-CoV-2 reemerged in the Auckland region, resulting in a managed border with the rest of the country being established to contain the disease. A single person, who was infected with the Delta variant in Auckland, travelled south 500 km to the city of Palmerston North, Manawatu, where they subsequently tested positive and remained in isolation for 18 days in October 2021. SARS CoV-2 was successfully detected in wastewater samples collected 5–7 October 2021. There were no other COVID-19 cases in Palmerston North for at least 6 months prior and 2 months after this case. SARS-CoV-2 RNA was not detected in any of the 23 wastewater samples tested from Palmerston North in July, August, and September 2021, nor in another 32 wastewater samples collected between 12 October 2021 and 3 February 2022. This is evidence of the very sensitive detection of SARS-CoV-2 RNA from a single infected person in wastewater from a city of 90,500 people with a daily average production of 35 million litres of sewage.
Gilpin et al. (Sat,) studied this question.