Dear Editor,
Upadhyay and Maroof[1] simplify emerging and re-emerging terminologies amid the COVID-19 pandemic in the Dec 2020 issue of the Journal. They explore various common terms, meticulously trace their origin, and extrapolate their pathways till the current era. There under the heading “WHO recommendations for Covid-19 quarantine”, the authors write that traveling nearby, that is within 1 m separation from a COVID-19 patient in any kind of conveyance is defined contact, and then quarantine should be implemented.
That is because infectious droplets emitted by an infected patient usually drop within that distance. However, now we are realizing that besides droplets, aerosols too play an important role in disease transmission.[2] Once suspended in the fluid medium of an enclosed space, they travel beyond that distance and pose a risk to persons occupying that area. As several modern transport vehicles have enclosures providing their passengers the comfort of air conditioning, the risk of this mode of transmission inside needs serious consideration for mitigation purposes. Under the title of “Risk of Covid 19 during air travel”, Pombal and Powell write on the JAMA patient page in Oct 2020 issue that the risk of infection transmission inside an aircraft is low.[3] However, concerns are raised by readers on the same page regarding the conflict of interests of the authors. Hence, we need more information from reliable and independent industry experts on this matter.
A simple solution to aerosol dispersion is ensuring proper ventilation in enclosed chambers.[4] This principle should guide us while traveling when it is not possible/feasible/sustainable to travel alone. It also holds true when hiring taxi cab services which is an increasing phenomenon in our metro cities. As either a passenger or a driver may harbor presymptomatic or asymptomatic infection, it is wise to switch off the AC system and open all the windows of the vehicle so as to reduce the viral load of the air inside. When due to inclement weather that is not possible, researchers guide us to minimize the risk of cross-transmission by analyzing aerodynamics inside the motor vehicle.
Varghese Mathai et al.[5] of the University of Massachusetts, MA, USA make an assessment of computational flow dynamics of various combinations of open and closed windows of a moving vehicle and figure the best way out to safety. They find intuitively that the best way of traveling is opening all the windows and the worst mode is closing all of them. But when a driver and a single passenger are the two occupants only, and they open windows of their side, it provides less safety than when they open those of far/opposite sides. Its reason is that when both of them open windows of their proximity alone, incoming air faces resistance to entry inside. Conversely, when each one of them opens windows of the opposite side, the resistance is not there, and there is a free flow of air leading to a higher number of air changes. Knowledge of this nuance of fluid mechanics may guide us when traveling is essential while breathing shared air inside a compartment to reduce the risk of infection.
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References
- 1.Upadhyay MK, Maroof KA. Understanding the emerging and reemerging terminologies amid the COVID-19 pandemic. J Family Med Prim Care. 2020;9:5881–7. doi: 10.4103/jfmpc.jfmpc_960_20. [DOI] [PMC free article] [PubMed] [Google Scholar]
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- 3.Pombal R, Hosegood I, Powell D. Risk of COVID-19 during air travel. JAMA. 2020;324:1798. doi: 10.1001/jama.2020.19108. [DOI] [PubMed] [Google Scholar]
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