2 patients with false negative tests root of COVID-19 outbreak in Halifax hospital in May, probe finds

COVID-19 spread between patients at a Halifax hospital in May after two people who had been admitted with respiratory symptoms initially tested negative, an investigation by the Nova Scotia Health Authority has determined. 

In all, 21 patients of a non-COVID unit at the Halifax Infirmary site tested positive and six people died during the outbreak, which was declared May 12.

The health authority said in a news release Thursday that it started looking into the cause of the outbreak while it was underway and the work included reviewing patient charts, room placements, staffing assignment as well as analyzing the molecular data of the viruses.

It said the laboratory analysis of the strains of the virus confirmed what was thought to be the case early on: that the cases fell into different groups. 

Out of the 21 patients, 17 of the cases could be traced back to two people who initially tested negative for COVID-19 even though it was later determined they'd been infected with the virus. Genetic tracing showed the two were the source of infections in at least 15 other patients, the investigation found.

For technical reasons, data from two of the 21 people could not be analyzed. 

3 deaths result of COVID-19 

The investigation also found two patients contracted COVID-19 in the community and didn't spread it to anyone else. One of those people died because of the virus.

Of the other five people who died, the health authority said in three instances, the patients had COVID-19 but other health issues caused their deaths. Two other people who were infected died as a result of COVID-19. 

Most of the people in the unit who contracted the virus were not vaccinated and had other medical conditions that left them vulnerable to COVID-19 and severe illness, said the health authority release. 

The health authority said 12 staff tested positive and genome sequencing found 11 of those cases were linked to the outbreak.

"Although initial transmission of infection was likely from a patient transmitting to staff subsequent to the recognition of the outbreak, it was not possible to identify all of the transmission sources among all of the staff," spokesperson Brendan Elliott said in an email. 

Shared rooms a risk factor

Analyzing the circumstances of the outbreak has led the health authority to determine that shared rooms were a risk factor and a negative test was not reason enough for staff to stop taking contact and droplet precautions, it said. Those precautions included wearing masks, maintaining physical distancing and keeping patients in the area of their bed. 

Another issue was patients who wandered. The investigation found that increased the risk of infection for the people sharing a room with them. As a result, the health authority said inpatient units need to have enough resources to manage the patients who wander, similar to the strategies used to manage people with dementia.

In response to the outbreak, the health authority said it is recommending that single-patient rooms be the standard for any new or renovated hospital. It also said it is sharing the lessons learned and best practices for infection prevention and control across the province. 

During the outbreak, the hospital moved patients who tested positive to the COVID-19 unit. All patients who had been in the Infirmary unit where the outbreak occurred were tested at regular intervals and there was facility-wide testing.

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