There might be more silent cases of coronavirus than first thought, according to new research.
The research, published in British Medical Journal’s respiratory publication Thorax on Wednesday, looked at a ship which departed Argentina in March for a 21-day cruise.
It left just as the World Health Organisation announced the pandemic.
Of the 217 passengers and crew on board the ship, 128 tested positive for COVID-19 after a passenger first became feverish eight days into the cruise.
But only 24 were symptomatic, eight required medical evacuation, four were intubated and ventilated, while 104 were asymptomatic, meaning they showed no signs of the virus at all.
The 104 make up 81 per cent of those who test positive – higher than the research which showed 50 per cent were asymptomatic in April.
Thorax editor Professor Alan Smyth said it was “difficult” to find COVID-19 patients who had no symptoms.
“As countries progress out of lockdown, a high proportion of infected, but asymptomatic, individuals may mean that a much higher percentage of the population than expected may have been infected with COVID,” Prof Smyth said.
Many Australian states will have restrictions easing even further from next week.
While it might be concerning, virologist Professor Ian Mackay, from The University of Queensland, told Yahoo News Australia in a live Q&A last month asymptomatic spread was just like any virus.
“The same sort of thing happens with influenza,” he said.
Cruise ship infection ‘significantly underestimated’
The researchers added the results of the study showed that infection on affected cruise ships was “likely to be significantly underestimated, and strategies are needed to assess and monitor all passengers to prevent community transmission after disembarkation”.
The Ruby Princess debacle has led to cases across the country after passengers were allowed to disembark on March 19 as it docked in Sydney.
A woman on board the ship tested positive to coronavirus and was suspected to have carried the "dormant" virus for almost 10 weeks before falling ill.
The woman was diagnosed in Cairns on Monday.
Authorities suspected she was the latest coronavirus case to have carried the inactive virus and became sick weeks after exposure.
Six crew members on board the Al Kuwait live export ship, which is currently docked in Fremantle in Western Australia, have also tested positive to the virus.
Premier Mark McGowan suspects more crew on board will return positive results.
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