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To Fly Or Not To Fly? The Odds Of Catching The Virus
About 50% of the air is taken in from the outside atmosphere through the engine and the rest of the 50% is re-circulated from within the cabin to maintain the humidity and temperature.
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The Russians have ignited a ray of hope, howsoever faint, by declaring their success with the development of the first coronavirus vaccine, Sputnik V. However, there is a lot of scepticism about its efficacy as large scale human trials have not been completed as per prescribed protocol. The commencement of the commercial production, and the hierarchy of countries and individuals getting access to the vaccine, is still very enigmatic and complicated.
Given the situation on the virus, and its probable cure, we are still in a quandary on whether or not to embark on travel? Not for tourism, but to take a flight to meet a sick family member? Or for urgent business? We do understand that most businesses are now opening up just to help revive the economy and not just because it is deemed safe. There is much deliberation on the risk of catching the infection during air travel. We fearfully calculate the risks -- the danger of being in a crowded, enclosed space perhaps in proximity of an infected individual or more, with no visible warning or danger signals. There are two aspects to be considered to assess in the risk-benefit ratio: the travel in the airplane per se and the associated, but integral, risk of travel – the transactions at the airport and the handling of the baggage.
Arnold Barnett, a professor at the Massachusetts Institute of Technology (MIT) has tried to quantify the odds of catching Covid-19 from flying using simulative technology. He has tried to factor in a number of variables, including the odds of being seated near someone in the infectious stage of the disease (with mandatory use of face masks) – the next seat, two seats away but the same row, across the aisle, one row in front or behind; and then taken into account the air ventilation in the flight. The air circulation in most commercial flights is very efficient with nearly a complete air exchange every two minutes. About 50% of the air is taken in from the outside atmosphere through the engine and the rest of the 50% is re-circulated from within the cabin to maintain the humidity and temperature. The cabin air passes through a High Efficiency Particulate Air (HEPA) filter, which can filter out 99.9% of the nano-particles, and carries negligible risk of transmitting infection. The flow of air is linear from the ceiling to the floor. The passengers sit facing forward and not towards each other, seat backs as barriers, the limited movement of the passengers once seated, were all considered. Barnett has postulated that about 1 in 4300 passengers had a chance of picking up the infection on a 2-hour flight, and the odds are about half that, 1 in 7700, if the middle seat is left empty! Interpreting it further, the odds of dying due to the infection contracted in a flight are much lower, 1 in 400,000 to 1 in 600,000 – depending on the age and associated risk factors. To put these statistics in perspective, the odds are comparable to the average risk of a 2 hour exposure on the ground but still very high compared to the 1 in 34million odds that a flight would end in a deadly crash. These results are still only non peer-reviewed preprints. To add chaos to all these calculations are factors that the virus inoculous from the infected person could reach the co-passenger before it could be filtered; the flow of air is not always completely linear if there is excessive movement by the infected passenger; frequent movement of the crew coming in contact with different passengers; sneezing and coughing droplets could travel a variable distance ( the smaller droplets can stay suspended and travel up to 16metres) if flow not impeded into an elbow and many other conceivable alterations to the airborne route of transmission in an actual flight.
The surface transmission within the flight is another major source of concern. The tray tables, the service trolleys, the snack trays as well as individual items can pose a great risk. The use of the lavatories; from the crowded queues to use them, direct touch of the door handle, bathroom faucet, slider to lock to the toilet flush can be sources of infection. The risk is amplified manifolds when the face masks are set aside at the time of food service, with the animated chatter that follows and re-institution of the masks after a questionable period of time. The frequent movement of the passengers and crew within the aisles also cause the airflow to tumble and the linear flow is disrupted. The prevalence of the infection at the place of boarding the flight is crucial to assess the risk and confounded by the fact that the passengers may have travelled to high risk zones prior to embarkation. And God forbid if there is a super-spreader on board!
The airports with the long queues at every point – entering, check-in counters, security checks, boarding tunnels and gates or the buses and the baggage conveyor belts pose a visible threat within the confined spaces inspite of the emphasis on social distancing. The airport restaurants, coffee bars and self service snack vending machines; close seating at the gate terminals; the attractive shopping; trips to the washrooms or the water fountains; the droplet containing fomites stirred up while walking on the carpets; the wheelchairs and golf carts to ferry passengers. The intermingling of passengers who have travelled from variable infected risk zones and possible face-to-face or close contact interactions between them spell disaster for the passengers and the contacts they meet after exiting the airport. The usage of shared cabs is another source of possible infection transmission. The list of probable sources of infection is exhaustive and endless.
A panel constituted by an array of experts, including an infectious disease doctor, an ER doctor, a pilot, a medical advisor for aviation trade association and a frequent-flyer deal have given suggestions to mitigate transmission of infection. They suggest screening of passengers and flight attendants for symptoms, compulsory use of face masks, the “middle seat” should be kept empty, the seating should be row-wise, minimum movement of passengers and cabin crew within the flight, avoiding queues to the lavatories, deep cleaning of all touch points in the aircraft by the airline staff and again by the passenger, having the vent open above to blow air, no pets to be allowed, all baggage to be checked in only and to avoid food or even water service. The “middle seat” empty translates into considerable losses for the airlines which are already stretched on budget. They have come up with innovative ideas like the option of purchasing an extra seat or a private row by the passenger and keeping it empty; letting a relatively younger passenger with no co-morbidities travel on the middle seat after donning a full PPE throughout the flight at a slightly discounted ticket price. The seats fabric are being changed to synthetic leather to minimise penetration of the surface by viruses and also easier to wipe down, the crew and officials are required to undergo mandatory health check-ups and wear protective gear. They do have plans for plastic dividers between seats and in-flight janitors. The queuing and airport terminal risks are getting minimised by allowing face recognition software to secure entry, mobile boarding cards, online pre-delivered baggage tags and passengers are advised to have multiple digital payment apps on their phones to avoid cash transactions on the airport, avoid use of trolleys and are encouraged to use the washrooms at the airport rather than in the aircraft. In India, Arogya Setu app on the phone is compulsory. Blockchain e-passports by the likes of ShareRing are coming up to ensure safety of travel and onward seamless communication to all agencies involved in the travel.
With the restrictions getting lifted, the quarantine fatigues are spiking. Air travel is definitely not as low risk like going to the local grocery store or for a stroll in the neighbourhood. It poses a moderate risk, even with all the precautions. Infected people do get on the planes but there has not been any concrete evidence to suggest that those on the flight got infected. Moreover, there are more suggestions of catching the infection on the terminal or when meeting up with contacts after the travel. Age and other risk factors need to be assesed before contemplating travel. The longer the flight, the longer the possible exposure, hence the risk. It is really like a ‘draw of cards’ – you may be unlucky to be seated next to an infectious person, who is asymptomatic, as the symptomatic ones are screened out at the terminal itself!
My recommendation as a doctor: travel only if you must. Non-essential travel is neither desirable, nor is it recommended.
Disclaimer: The views expressed in the article above are those of the authors' and do not necessarily represent or reflect the views of this publishing house. Unless otherwise noted, the author is writing in his/her personal capacity. They are not intended and should not be thought to represent official ideas, attitudes, or policies of any agency or institution.