Was it airborne? Queensland's Covid outbreak and mystery of hospital ward 5D
The mystery coronavirus infections of healthcare workers at Princess Alexandra hospital’s ward 5D continues to spook Queensland health authorities.
Late on Wednesday, all hospital staff members who entered the infectious diseases ward from Tuesday to Friday last week – whether or not they came into contact with patients – were ordered into quarantine.
The ward is central to understanding how UK-variant coronavirus cases entered and subsequently spread in the Brisbane community, prompting a three-day citywide lockdown and restrictions in two states.
The first case was a doctor, who assessed a patient for potential admission to the hospital on 10 March.
The second and third were nurses on ward 5D – both contracted coronavirus from a patient returned from India, with whom they had no direct contact. Genomic testing has confirmed the traveller is the source of both cases.
The patient was brought into ward 5D at 8.30pm on 23 March. The first nurse to be infected did not begin her shift until 10pm. She did not enter the man’s room or otherwise have contact with him.
This week, the Queensland chief health officer, Jeanette Young, speculated on how the first nurse became infected.
“There is most likely some environmental contamination or some aerosolisation of the virus when the person was admitted,” Young said.
Experts say there are other possibilities, which help to explain the steps taken this week to evacuate ward 5D, limit admissions to the rest of the hospital and to place a large number of healthcare staff in quarantine.
One is that an asymptomatic or undetected case acted as a link between the traveller and the infected nurses.
Another is that the airborne infection might have been contracted outside the ward, where people were likely to be less vigilant.
Thea van de Mortel, an infection control expert and the deputy head of Griffith University’s school of nursing, told Guardian Australia there was a growing understanding of the way coronavirus can be transmitted via the air, potentially over long distances and times.
“This is a pathogen that spreads through very small particles in the air [and] there’s a limit to what non specially-designed facilities can do,” van de Mortel said.
“There’s some suggestion that for the people who caught it … they don’t necessarily think it was caught in the Covid ward, that it may have been caught outside.
“When you open the door, some of the contaminated air will escape.”
Van de Mortel said new variants of the virus – including the UK-variant contracted in Brisbane – resulted in larger viral loads within infected persons. “B117 [the UK variant] is much more transmissible than the ordinary virus. Really, the key thing is to get people vaccinated.”
Unions representing nurses and doctors, and the Australian Medical Association, have called for an investigation into the infections, including whether safety equipment was properly fit-tested.
While the community outbreak in Brisbane appears to be under control, there remains concern about the extent of cases within the hotel quarantine and hospital system. Nine new cases detected in returned travellers were announced on Wednesday.
In a further attempt to lessen the risk in hospitals, the federal government has agreed to halve the number of international arrivals to Queensland.
Young told reporters on Thursday she was not concerned about the capacity of the health system to cope with cases.
“What I’m concerned about is the amount of virus people have,” she said.
“People have an enormous amount of virus. We know the risk is extraordinarily high. We are getting more and more of these extraordinarily high-risk patients in these hospitals.
“It is so easy for one tiny, tiny error to lead to the contamination of a healthcare worker. That’s why it is so critical … to halve the numbers of travellers coming into Queensland.”