Pre-Flight Testing Is Not Preventing COVID-19 Spread on Airplanes

Researchers are warning about the risk of COVID-19 spreading on planes, even when passengers are tested beforehand. The advisory stems from a case report from the Centers for Disease Control and Prevention (CDC) involving passengers on a September 2020 flight to New Zealand.

The case report, which was published in the CDC's journal Emerging Infectious Diseases, analyzed an 18-hour flight of citizens and permanent residents who were returning to New Zealand from Dubai, United Arab Emirates.

The flight contained 86 passengers who came from five different countries before their layover in Dubai. Some of the passengers were tested for SARS-CoV-2 (the virus that causes COVID-19) during a layover stop in Malaysia. Once they arrived in New Zealand, the passengers were required to undergo managed isolation and quarantine for 14 days, along with testing for SARS-CoV-2.

Richard Watkins, MD, an infectious disease physician in Akron, Ohio, and a professor of internal medicine at the Northeast Ohio Medical University, tells Verywell that the case report's findings “underscore the recommendations not to fly.”

Watkins adds that the length of the flight also matters: “The longer the flight, the greater the risk.”

How Many Passengers Got Sick?

Of the 86 passengers, seven tested positive for the virus in quarantine—and five of those passengers had tested negative for SARS-CoV-2 before their flight.

The infected passengers were seated within four rows of one another during the 18-hour flight. Masks were optional during the flight and, while five of the infected passengers wore masks and gloves, two did not. 

When the researchers analyzed the data collected on the infected passengers, they noted that the genetic sequencing of the SARS-CoV-2 virus that they were infected with was “genetically identical,” except for a single mutation in one sample. The researchers concluded that it’s likely that the passengers were infected on the flight.

How Did the Virus Spread?

The researchers theorize that two passengers who had traveled together from Switzerland—and tested negative for SARS-CoV-2 three days before leaving the country—were the source of the infections. One of the passengers was the first to report symptoms of the virus in quarantine and tested positive the next day. 

The researchers concluded that evidence of transmission on the flight was "strongly supported by the epidemiologic data, in-flight seating plan, symptom onset dates, and genomic data for this group of travelers who tested positive for SARS-CoV-2."

The case reports also highlight “some of the complexities of determining the value of pre-departure testing," according to the researchers.

Other Cases of COVID-19 on Planes

The new case report isn’t the only one to document in-flight transmission of COVID-19. Another case report that was published in Emerging Infectious Diseases in November 2020 detailed how 16 people tested positive for SARS-CoV-2 after a 10-hour flight from London, UK, to Hanoi, Vietnam.

The researchers conclude that "the risk for on-board transmission of SARS-CoV-2 during long flights is real and has the potential to cause COVID-19 clusters of substantial size."

Does Pre-Flight Testing Help At All?

John Sellick, DO, MS, an infectious disease expert and a professor of medicine at the University at Buffalo/SUNY, tells Verywell that the case report raises a lot of questions about the value of pre-flight testing.

“This is a disease with an incubation period that can be up to 14 days,” Sellick says. “All the pre-travel testing does is pick off the people who are obviously sick.” While Sellick says that there’s “some value to that,” he adds that pre-flight testing “doesn’t give you a get-out-of-jail-free card.”

Sellick says that the biggest issue with flying and COVID-19 transmission is that “people on a flight are all so close to one another." He adds that even the special air filtering systems used in many airplanes “don’t help when somebody is a foot away from you and they’re sick."

Current Travel Guidelines

As of the beginning of March, all people coming to the country by plane are required to have a negative COVID-19 test result or documentation that they recovered from COVID-19 before they board a flight to the U.S. Masks are also required on all public transportation traveling into, within, or out of the U.S., as well as in hubs like airports and stations.

However, the CDC warns against travel in general, noting that “travel increases your chance of getting and spreading COVID-19.”

While you are traveling, the CDC stresses the importance of continuing to follow COVID-19 safety precautions like wearing a face mask, social distancing as much as possible, and practicing frequent, proper hand hygiene.

What If You Need to Travel?

Overall, Sellick says that flying during the pandemic is a “value judgment for people,” noting that there’s “only so much you have control over” when you're in the airport and aboard a flight.

If you do decide to fly during the pandemic, Sellick recommends doing your best to space out from other people while you're in the airport and waiting to board, avoid larger planes (if possible), wear a mask and eye protection, and use hand sanitizer.

“If I had to go somewhere for a family emergency, I would do it,” Sellick says. “But it’s not [the] time for travel for fun just yet.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.