How safe is it to fly in the age of Covid-19? The question has been the subject of debate for almost two years. The airline industry has argued that the risk to passengers is very low; independent researchers have tended to say that it’s not high, while stipulating that it’s impossible to assess with real accuracy. Whatever the odds of getting infected by the coronavirus on a plane, they’ve grown worse with the spread of the omicron variant.
1. How many fliers have caught the virus?
It’s impossible to know. In October, a group of researchers published a paper in the Journal of Travel Medicine in which they tallied 64 cases of in-flight transmission documented in studies published roughly during 2020. But any count of known cases will reflect the difficulty establishing the spread of a virus on a plane.
2. Why is it hard to establish?
It involves knowing a passenger was infected, interviewing and testing as many as hundreds of fellow fliers, then, ideally, analyzing the genomes of any additional viruses that turn up to check for connections to the first passenger’s infection. That’s a huge research project, impossible to undertake with every known case of someone flying while capable of infecting others with the coronavirus. A study published in March found that 14% of wastewater samples from 198 commercial planes arriving at Dubai Airport tested positive for the presence of coronavirus genes, suggesting at least someone on board was infected.
3. What can make flying risky?
As with other forms of public transport, the risk comes from close proximity to others. Those infected with the novel coronavirus emit virus-containing droplets from their noses and mouths that can be transferred directly to someone nearby. More rarely, infection can be caused by contact with surfaces contaminated with droplets. Studies of other viruses that spread the same way have found that the greatest risk on a flight comes from sitting within two rows of a contagious person for longer than eight hours.
4. What about airborne transmission?
The coronavirus also can be transmitted via smaller particles that people emit from their noses and mouths. Known as aerosols, they can float through the air and be inhaled. The airline industry says modern aircraft ventilation should mitigate the risk of this sort of spread. The air on a plane is generally a 50-50 mix of sterile outside air and recirculated cabin air that’s been filtered. Airbus SE and Boeing Co., the world’s two biggest planemakers, say that since the 1980s they have been fitting their aircraft with HEPA filters, which capture particles as small as the virus. Some older aircraft, however, use less efficient filters. Cabin airflow goes from ceiling to floor rather than front to back and is split into sections, which should limit the movement of particles along the length of the plane. Even so, modeling suggests this airflow can be influenced by factors such as seat and cabin layout and how full the aircraft is. Also, these ventilation systems may not be fully operational when planes are parked at the gate; an influenza outbreak in 1979 resulted from passengers being kept on board a grounded aircraft with the ventilation turned off. Some airlines say they are now keeping the systems turned on until everyone exits the aircraft.
5. How does omicron change things?
Omicron is more transmissible than earlier versions of the coronavirus, so it’s easier to catch from someone who’s infected with it, whether on an airplane or anywhere else. U.K. data showed the probability that someone with an omicron infection will spread it in a household was three times that seen with delta, the variant that became the dominant strain worldwide in mid-2021, while the risk for spread to a close contact was double. David Powell, physician and medical adviser to the International Air Transport Association, which represents almost 300 carriers, has estimated that aircraft passengers are two to three times more likely to catch the coronavirus during a flight since the emergence of omicron.
6. What can passengers do to reduce risks?
• Get vaccinated: Full vaccination against Covid, plus a booster shot, if available, offers the best protection against the virus in any setting.
• Mask up: Public health specialists increasingly have urged people to wear medical-grade masks, preferably the tight-fitting type known as respirators but at least surgical masks, rather than cloth ones. If it’s necessary to remove a mask to eat or drink, some researchers suggest waiting until those nearby have already done so and have replaced their face coverings. In a study published in March, researchers estimated that taking off a mask for an hour-long meal service on a 12-hour flight increases the average probability of infection by as much as 59%, compared to masking continuously. Authors of an article in the Journal of Travel Medicine recommended that passengers keep their masks on in the lavatory.
• Keep your distance: As much as possible, it’s important to maintain a distance from other people and to avoid face-to-face contact especially. A study published in Germany in mid-2020 concluded that passengers could reduce contact with one another, and thus the potential for spreading the virus, by bringing fewer and smaller bags on board.
• Don’t relax your guard: Navigating the airport also requires vigilance as travelers wait in queues, check in for flights, visit food vendors and use bathrooms.
7. Does it help to turn on the personal air vent?
It’s not clear. The planemaker Embraer recommends that fliers use the vent, also known as a gasper, to blow air directly toward their seats. The company said its tests show this creates an airflow routing particles to the air-return grills on the cabin floor and minimizing contamination between rows. But a 2020 study led by the U.S. Defense Department’s Transportation Command concluded that whether the gasper is off or on has no significant impact on the risk of aerosol transmission on planes.
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