Coronavirus cases linked to long air flights at start of pandemic, studies find

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Two small studies carried out in the early stages of the pandemic found a direct link between traveling on a long flight where masks were not needed and testing positive for COVID-19.

But an important caveat is that the studies did not measure the effects of wearing masks on airplanes, as they were conducted before the major airlines introduced mask warrants.

Additionally, since the studies were conducted in March, many airlines, including JetBlue JBLU,
-8,77%,
Delta DAL,
-9,19%
and southwest LUV,
-5,80%
blocked the middle seats on flights to create space between passengers. Many major airlines have also introduced other health security protocols, including contactless check-ins and more stringent pre-flight checks of passengers for symptoms of the coronavirus or contact with people who may have the virus.Related: If airlines keep the middle seat empty over fears of coronavirus transmission, will air travel become more expensive?

Is the coronavirus airborne?

Initially, the United States Centers for Disease Control and Prevention said the main way the coronavirus spread was via respiratory droplets that can infect a person who is within six feet of someone who has contracted the virus. virus.

But the CDC recently changed its guidelines to say the virus can spread through the air and therefore can be contracted by inhaling particles of air that contain viruses. These form “when a person who has COVID-19 coughs, sneezes, sings, speaks or breathes,” the agency said.

The agency abruptly removed the language from its site on Monday, saying it had been “posted by mistake on the agency’s official website.”

“The CDC is currently updating its recommendations regarding airborne transmission of SARS-CoV-2 (the virus that causes COVID-19),” the CDC’s website said Monday afternoon.

(The agency did not directly respond to MarketWatch’s request for comment.)

It wouldn’t be the first time the agency has turned the tide in a remarkable way during the pandemic.

In March, CDC officials said the general public should not wear masks; it then reversed its course. And just a few weeks ago, the agency reversed its recommendation that asymptomatic people who have come in contact with someone who tests positive for the virus do not need to be tested.

The CDC has supported throughout the pandemic that traveling increases your chances of “contracting and spreading COVID-19” and that “staying at home is the best way to protect yourself and others from COVID-19 The CDC says on its site.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases for three decades, told MarketWatch in an interview in July that he wouldn’t be getting on a plane anytime soon, given that at 79, he is “endangered Category”

However, the CDC says on its website that the new coronavirus and other viruses “do not spread easily on flights because of the way the air circulates and is filtered on planes. But flying remains a problem because “social distancing is difficult on crowded flights, and sitting within 6 feet of others, sometimes for hours, can increase your risk of contracting COVID-19.”

What new studies have shown

A study has traced four cases of illness transmitted by the coronavirus COVID-19 to a 3-hour flight from Boston to Hong Kong on March 9. Two passengers were a married couple who were hospitalized on March 15 after testing positive for the virus. The other two cases were flight attendants, one of whom served the couple during the flight.

Genetic analysis of virus samples from all four people revealed “100% identical” genetic sequence, wrote an international group of researchers from the London School of Hygiene & Tropical Medicine and the University of Hong Kong and others. institutions, in a peer-reviewed study in Emerging Infectious Diseases, a journal published by the CDC.

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“While we cannot completely rule out the possibility that patients C and D were infected prior to boarding, the unique viral sequence and 100% identity across the entire virus genome of the 4 patients make this scenario highly. improbable “
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The researchers concluded that the married couple likely contracted the virus in North America before boarding the plane and passed it on to flight attendants (called patients C and D in the study).

“Although we cannot completely rule out the possibility that patients C and D were infected before boarding, the unique viral sequence and 100% identity across the entire virus genome of the 4 patients make this scenario highly unlikely.” , wrote the researchers. “We therefore conclude that these 4 patients belong to the same chain of transmission in flight.”

No other cases of coronavirus associated with this specific flight have been identified, according to the study. In addition, the researchers were “unable to quantify the virus attack rate on this flight because not all passengers were tested.”

A second study, also published in the November edition of Emerging Infectious Diseases, tracked 12 cases on a 10-hour flight on March 2 from London to Hanoi, Vietnam. A total of 217 people, including passengers and crew, were on board the flight.

The 12 people who tested positive for the virus were seated in business class, where the only passenger symptomatic of the flight was also seated, according to researchers from Vietnam and Australia, the majority of which are affiliated with the National Institute of Hygiene and epidemiology of Hanoi.

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Given that all 12 of those passengers were departing directly from the UK at a time when the country has only reported 23 confirmed cases of the coronavirus, the authors conclude that it is very likely that they contracted the virus on the flight. .
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Unlike the previous study, this one did not perform a genetic analysis to confirm identical viral sequences to verify whether the 12 passengers probably contracted the virus from the symptomatic passenger of the flight.

However, given that all 12 of those passengers departed directly from the UK at a time when the country had only 23 confirmed cases of the coronavirus, the authors concluded that it is very likely that they contracted the virus on the flight.

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“The risk of on-board transmission of SARS-CoV-2 during long flights is real and has the potential to cause COVID-19 clusters of substantial size, even in business class environments with spacious seats far beyond of the established distance used. to define close contact on airplanes ”
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‘Although the testing was not implemented on a large scale across the country at the time, community transmission in the UK was not yet widely established, making it unlikely that more than one edge incubating disease, ”the researchers wrote.

Related: Come back, Americans: Calls for an urgent US-UK airlift as airlines hit by new lockdown fears

“The risk of on-board transmission of SARS-CoV-2 during long flights is real and has the potential to cause COVID-19 clusters of substantial size, even in business class environments with spacious seats far beyond of the established distance used. to define close contact on planes, ”they concluded. “As long as COVID-19 presents a threat of a global pandemic in the absence of a good point-of-care test, better onboard infection prevention measures and on-arrival screening procedures are needed to make the safe flight.

As of Monday, COVID-19, the disease caused by the SARS-CoV-2 virus, had infected 31.2 million people worldwide and 6.8 million in the U.S. It had killed nearly a million people in the world and at least 200,000 in the United States, according to Johns Hopkins University.

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