Virus cluster triggers concerns about asymptomatic carriers


A CAIRNS Hospital coronavirus cluster has been sourced back to a Brisbane-based engineer contractor who visited the facility's Pathology Queensland laboratory more than a month ago, triggering concerns about asymptomatic cases unknowingly spreading the new virus to others.

Three laboratory workers have tested positive to the virus in serology testing, which picks up antibodies produced in blood, showing they have previously been infected and recovered.

Queensland Chief Health Officer Jeannette Young said the three workers had mild or no symptoms of the novel coronavirus and did not realise they had the disease.

Queensland Chief Health Officer Dr Jeannette Young. Photo: Liam Kidston
Queensland Chief Health Officer Dr Jeannette Young. Photo: Liam Kidston

"As a precaution, they have been placed in self-quarantine, even though they are not feeling unwell or likely to be infectious," Dr Young said last night.

"Cairns Hospital is starting to screen all staff working from today to determine if there has been wider transmission.

"It is important to understand that there is a low risk of further transmission but we need to make every effort possible to ensure this disease does not spread further."

Serology testing, which picks up signs of the body's immune response to the virus, was ordered after a Cairns Hospital pathology worker was diagnosed with COVID-19 last Thursday.

The Cairns cluster of four cases has been traced back to a Brisbane-based engineer who worked in the hospital's pathology laboratory to service a biochemistry instrument on March 19 and 20 and tested positive to the new virus in early April.

He had also visited the Ipswich Hospital Pathology's Queensland laboratory, where eight staff were placed in quarantine.

But because about two weeks had passed between the technician's visit to the Cairns Hospital laboratory and his positive test, workers there were not considered at risk and so were not required to go into quarantine for 14 days.

Tropical Public Health Services has contacted almost all of the more than 250 people who have swiped into the Cairns laboratory since the engineer's visit.

Dr Young appealed to anyone in Cairns, who had respiratory symptoms, such as a cough, shortness of breath, sore throat or fever to get tested for COVID-19 by contacting their general practitioner, their nearest hospital emergency department or by visiting a drive-through fever clinic.

"We haven't seen a lot of cases in Cairns, I would suspect if there was a widespread problem that we would have seen a lot more cases because Cairns has had community testing for any symptoms of COVID-19 in place now for two weeks," she said.

But the problem of asymptomatic cases spreading the virus unknowingly is a problem that remains a concern for scientists.

Brisbane-based infectious disease specialist David Paterson said: "We do know that some people may not have symptoms and for a period of probably about 24 to 48 hours may actually be shedding the virus and be potentially infectious to other people.

"We really do have to maintain our vigilance."

Last night, the number of Cairns cases of the new virus remained at 33 out of the state's total of 1024 infections.

Under Australian protocols, people picked up in serology tests after they have recovered from the virus, are not yet included in national or state data.

Originally published as Cairns hospital cases traced to Brisbane worker

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