To date there have been 342 confirmed cases of COVID-19 diagnosed in NSW in passengers who all acquired their infection while on, or in some cases, possibly before boarding the Ruby Princess cruise.
Transmission of COVID-19 amongst these passengers could not have been prevented by NSW Health staff. No cases of COVID-19 were identified on board the ship before it docked.
The vast majority of these passengers reported they did not develop symptoms until after leaving the Ruby Princess.
All passengers were advised to self-isolate for 14 days following disembarkation, which NSW Health has confirmed was provided by the Federal Department of Agriculture, Water and Environment.
Probable secondary transmission has been limited to 11 confirmed cases as of 3 April.
International experience shows COVID-19 can rapidly spread among passengers if left on board, so self-isolation at home is a much safer option than leaving passengers on board.
NSW Health had prepared plans in the event COVID-19 being identified on a cruise ship.
On this particular voyage, it was known that influenza activity had been identified on the ship.
The Ruby Princess was assessed as low risk, based on the level of illness on board, the negative COVID-19 tests done on passengers while in New Zealand, and the positive influenza tests done on a large proportion of the passengers with influenza like illness.
The risk assessment process recognised that there is no “no risk” setting for COVID-19, but balanced the level of risk against the benefit of removing passengers from a cruise ship on which the virus could be circulating.
Rapid influenza tests identify only a proportion of people who actually have the infection, meaning some people return a negative result even though they are infected with the flu. The illness and test results identified on board was consistent with influenza.
This is reflected in email correspondence between NSW Health and the ship’s doctor on the Ruby Princess who confirmed influenza was circulating on the cruise. However, in two sick patients referenced in the email, although they had tested negative to influenza, the cause of their respiratory infection was consistent with influenza for which they were receiving treatment.
The reasons for ambulance transport requested by the treating doctor to NSW Health’s assessment panel, were, one passenger had a heart condition likely caused by an infection which was responding to influenza treatment, and the second passenger was suffering severe lower back pain but was also receiving treatment for flu.
Under the Commonwealth Department of Health cruise protocols, an ILI outbreak is defined when ‘more than one per cent of the ships total passengers and crew have an influenza like illness’.
The Ruby Princess had 2647 passengers and 1148 crew. The ship reported to NSW Health there were 104 acute respiratory infections of which 36 people had presented to the ship’s clinic with influenza like illness during the cruise and its numbers fell short of the definition of an ‘outbreak’.
The Commonwealth Department of Health protocol on managing novel coronavirus disease (COVID-19 risk from cruise ship) states “provided there are no concerns about the COVID-19 risk profile of the ship or suspected COVID-19 cases reported …the ship may be allowed to continue voyage while samples are tested”.
