A new report has found the Christchurch Sudima Hotel managed isolation facility was "severely stress-tested" by a high number of COVID-19 positive international mariners last year, with chain-smoking, double bunking and confined spaces among the factors that caused the virus to spread, including to two healthcare staff.
In October and November last year, 31 Russian and Ukrainian marines staying in isolation at the facility tested positive for COVID-19. Two healthcare staff involved with the mariners' care also tested positive.
A report from Canterbury District Health Board looks at the management of the cases and found that the high number of "early and highly infective COVID cases" put pressure on infection prevention and control at the facility.
"This combined with behavioural challenges (chain-smoking and double bunking) and environmental challenges (inappropriate ventilation and confined spaces) led to a total of 31 confirmed cases in the mariners and two in New Zealand healthcare staff," the report says.
It says double bunking was the "single most important known risk-factor facilitating spread", almost certainly led to the infection of 12 of the mariners, and "was likely a contributing factor to the infection of two of our staff".
"This must not be allowed to happen again."
The authors also say the facility was not "set up to manage large numbers of chain-smoking guests", with more than 150 in the international marine cohort.
"If we have such a cohort again we need to consider hosting them in rooms with opening windows/balconies that don’t require them to exit the facility to smoke. Alternatively, we need considerably more staff to manage the physical distancing security requirements of such guests.
"This is a non-trivial issue - it was a significant contributor to the spread of COVID in this cohort and a significant stress on staff, not to mention the cleaning requirements post their exit."
The report says transmission to staff occurred despite "apparently rigorous adherence" to protocols and best practice use of personal protective equipment (PPE).
"Following a thorough source investigation, it seems likely that both transmission events occurred through exposure to small, airborne microdroplets emitted from the rooms of cases at or around the peak of infectivity."
However, while protocols at the time were "well designed" to address the risk of contact and droplet transmission, they were "less geared toward managing the risk of transmission via small airborne transmission".
Among a raft of recommendations, the report supported the "careful introduction of fit tested N-95 masks for staff working in quarantine wings and facilities along with a review of ventilation specifications in all quarantine wings and facilities".