Study bolsters case for COVID quarantine

pre-flight testing Canada
The testing area at Toronto-Pearson International Airport (Twitter/TorontoPearson).

A new study is providing support for federal quarantine policies for international travellers and casting doubt on the utility of pre-departure tests.

The study is due to be published in the March edition of Emerging Infectious Diseases from the Centers for Disease Control. But editors pushed up the publication to this month. It explains how COVID spread on an Emirates flight into New Zealand. And it shows how a 14-day quarantine prevented the disease’s spread into the community.

This study is important in Canada for two reasons. First, reports on COVID infections on aircraft are rare and this study shows how it might happen. Secondly, Canada has three key policies to stop the international spread of COVID. They include barring most non-Canadians, imposing a 14-day quarantine on international travellers, and COVID testing within three days of departure.

While not speaking directly to Canada’s policies, the researchers say their study shows quarantines are important to stop the spread of COVID.

A team of 26 researchers studied an Emirates flight from Dubai on September 28. Eighty-six people boarded flight EK448. It’s an 18-hour flight to Auckland, including a fuel stop in Kuala Lumpur. During that fuel stop, no one was allowed off the plane. The auxiliary power was down for about 30 minutes, cutting off the air flow in the plane. Researchers mention the outage, but did not venture an opinion if this may have had a impact on disease transmission.

Flight EK448

As usually happens on Emirates, passengers on flight 448 came from all over the world. Among the countries represented were Ireland, Ukraine, Switzerland, South Africa, and India.

Among the passengers were two people travelling together from Zurich, Switzerland. The pair told researchers they had negative COVID tests within 72 hours of their departure. They waited 9 hours, 27 minutes between flights in Dubai. They got on the Boeing 777 and sat in seats 26D and 26G. There was plenty of room for physical distancing – less than a third of the seats were occupied. The pair told researchers they wore gloves and masks throughout the flight.

And they would be the first people to report COVID symptoms.

After they landed in Auckland, the passengers got onto buses and headed to government quarantine facilities. One person went to Auckland and six went to a facility in Rotorua, about three hours south. Outside the buses, the only contact the passengers had was on the plane.

On October 1, the first person – identified as Passenger A – reported muscle pain and general weakness. Researchers believe that person would most likely have been infectious on the flight. Their travel companion – Passenger B – reported symptoms a day later and was likely infected at the same time.

Following procedures, health workers tested all of the passengers on October 2. At that point, they found a third infection in someone who felt no symptoms.

A second test

On October 4, a fourth passenger started to feel sick. “Reported symptoms included coryza, headache, muscle pain, general weakness, irritability, confusion, and a head cold,” write the researchers “This passenger had departed from Dublin, Ireland, and arrived in Dubai on September 28 at 9:05.” A test three days later revealed that person had COVID.

New Zealand procedures also called for health workers to collect a second COVID test on their 12th day of quarantine. When they did, they found another two cases. One final person, a travel companion, likely contracted COVID as the two shared a room in quarantine.

By the time the outbreak was contained, seven people tested positive for COVID. All of them sat in aisle seats within two rows of the first cases.

When taken together, the researchers conclude the evidence points to in-flight transmission. “These transmission events occurred despite reported in-flight use of masks and gloves,” they write. “These data do not definitively exclude an alternative exposure event, such as virus transmission at the Dubai airport before boarding (e.g., during check-in or in boarding queues). However, the close proximity of the relevant passengers on board suggests that in-flight transmission is plausible.”

quarantine study
A map shows where passengers from Emirates flight 448 sat on September 28 and 29, 2020. Coloured circles represent people who developed COVID after the flight. Blank circles show people who did not develop the disease (Emerging Infectious Diseases).

Study backs traveller quarantine

The study also bolsters the case for a quarantine period, the authors argue.

“That 3 passengers had positive test results on day 3 of their 14-day quarantine period indicates some of the complexities of determining the value of predeparture testing, including the modality and timing of any such testing,” the researchers conclude. “Although not definitive, these findings underscore the value of considering all international passengers arriving in New Zealand as being potentially infected with SARS-CoV-2, even if predeparture testing was undertaken, social distancing and spacing were followed, and personal protective equipment was used in-flight.”

A study by McMaster Health Labs in the fall found that one per cent of international travellers in Toronto tested positive for COVID. Most cases were detected at the airport with almost all cases detected within a week of arrival.

Airlines and airports have been calling for pre-departure COVID testing to shorten or eliminate quarantines.

“Canada already has one the world’s most draconian COVID-19 border control regimes, including travel bans and quarantines,” the International Air Transport Association said in early January, reacting to Canada’s imposition of pre-departure tests. “Even though COVID-19 testing is an internationally accepted risk-mitigation strategy, there are no plans to adjust the current 14-day quarantine rule nor eliminate the temperature checks airlines are required to perform on passengers wishing to travel to Canada.”

On Friday, Westjet blamed federal policies for route suspensions and job cuts.

Health Minister Patty Hajdu has defended Canada’s pre-flight COVID test requirement and quarantine period. She noted post-arrival trials in Toronto and Calgary would produce valuable data to guide future decisions.

But she indicated the quarantine will stay in place for the foreseeable future.

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Categories: Safety

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