Exploring opportunities for sewage testing on cargo ships as a tool to screen seafarers for COVID-19

Stringent border controls and surveillance measures have been an essential part of the New Zealand Government's response to the coronavirus disease 2019 (COVID-19) pandemic, particularly its elimination strategy, which requires all infected individuals arriving at the border to be identified and isolated to prevent incursions and community transmission. The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus that causes COVID-19 is shed in the faeces and other bodily secretions of infected people, and municipal wastewater-based surveillance for SARSCoV- 2 has been extensively utilised at both localised and community scales. This review article explores whether testing the sewage from cargo ships arriving at the New Zealand maritime border could be used in a similar way, serving as a screening mechanism to help protect the border. Whilst considerable knowledge gaps remain regarding the prevalence, onset and kinetics of faecal shedding of SARS-CoV-2, the available data suggest approximately half of infected individuals shed detectable levels of RNA in their stool, with the onset of shedding starting anywhere between the first and fifth week of illness. Engineering and health and safety considerations are also discussed. We conclude that testing sewage from ships is unlikely to detect cases of COVID-19 amongst crew with the reliability required by an elimination strategy, particularly given individual-level nasopharyngeal testing is readily administered to the relatively small crew aboard these vessels. However, other opportunities for testing sewage from ships for SARS-CoV-2 may exist, such as when border settings are relaxed and/or individuallevel testing is not practical or warranted (e.g., cruise ships), or in surveillance for other pathogens.