Coronavirus: woman found with virus after quarantine

Health authorities are investigating a cruise ship passenger found to have coronavirus after completing 14 days of quarantine in a Perth hotel.

The cruise ship Costa Luminosa

Health authorities are investigating the intriguing case of a cruise- ship passenger found to have corona­virus after completing 14 days of quarantine in a Perth hotel.

The 65-year-old woman was with family on the cruise ship Costa Luminosa in March when the virus broke out.

The ship docked in Italy on March 21 and the woman was among Australians flown home to Perth on a mercy flight on March 30.

The woman went immediately into forced quarantine in a hotel room in Perth and was released after 14 days but then she got sick. She was found to have COVID-19 late last week.

Her positive test result was reported in official West Australian Health Department figures on Saturday, April 25.

WA Health Minister Roger Cook said the woman could be among a number of isolated cases worldwide with an incubation period longer than 14 days.

“It is an interesting case,” Mr Cook said. “It is been investigated by the Department of Health.

“The Costa Luminosa docked in Italy on the 21st of March. And the person arrived in Perth on the 30th of March but became symptomatic after their 14-day isolation period.

“We understand the internationally understood regime is around a 14-day isolation period (and that) should see someone through the entire disease ­journey.

“So long incubation periods have been reported in the international literature but most of these are obviously single-case reports so it could be that this is just an extensive outlier.

“Another explanation could be that they recontracted or contracted the disease after they left the hotel through other means we are just continuing to investigate.

“I think this person travelled with family so they may have contracted it and been incubating it in their isolation period and then became symptomatic after they left isolation.

“There are a number of explanations that the Department of Health is investigating.”

Contact tracers in WA have been unable to find the source of the virus in just 16 of the 549 cases detected across the state. The Australian government uses the World Health Organisation advice that the COVID-19 incubation period ranges from one to 14 days, with a median incubation period of five to six days.

The federal Health Department acknowledges on its website that some coronavirus patients have a longer incubation period than average.

“The department is aware of reports that suggest there have been cases with longer incubation periods, such as 24 days,’’ the website states.

“The incubation period of infections often has a skewed distribution, where most patients have an incubation period that clusters around the average, but a few patients have a longer incubation ­period.

“Medical experts believe reports of cases with longer incubation periods are statistical outliers — while longer incubation periods are possible, they may have been reported in error, or had exposure to an unidentified case at a later date that has not been identified in a transmission chain.”