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Table 1 Characteristics of studies included in the qualitative synthesis

From: Hand hygiene and facemask use to prevent droplet-transmitted viral diseases during air travel: a systematic literature review

Author, year of publication Type of study Type of viral infection Setting (no. of passengers) Preventive measures Outcome(s) Main result(s) Quality level (score)a
     Facemask use/hand hygiene Other measures    
Caley, 2007 [20] Mathematical model Influenza Flight (10–400) Facemask use Border screening, immediate presentation following symptom onset, flight-base quarantining Time (days) of epidemic onset delay in an infection-free region following importation through air travel Median time delay (days) increased from 57 to 79 days at an R0 of 1.5 and from 17 to 20 days at an R0 of 3.5 Not available
Gupta, 2012 [21] Mathematical model Influenza Flight (21) N95 respiratorb use None Infection probability Infection probability was reduced from 15 to 0% (at 103 quanta per hourc) or from 100 to 55% (at 5226 quanta per hour) Not available
Nicolaides, 2020 [22] Mathematical model Influenza Flights moving through a network of (unspecified) international airports Increasing the percentage of hand hygiene for air-traveling people at any time from 20% (i.e., one out of five people) to 30, 40, 50%, or 60% None Infection prevalence and total square displacement (TSD) Infection prevalence and TSD were reduced by 18.2–55.4% and 23.7–69.1%, respectively Not available
Zhang, 2013 [23] Case-control study Influenza A (H1N1) Flight 1 (274)
Flight 2 (144)
Facemask use and hand hygiene None Risk for infection transmission Wearing a mask during flight reduced the infection transmission risk (OR, 0.0; 95% CI, 0.0–0.7)
No difference in hand-hygiene compliance between infected and uninfected passengers
Medium (6)
  1. aThe quality of evidence for aircraft-related transmission was evaluated using the bias assessment tool proposed by Leitmeyer et al. [19]. Based on a score assignment, each study was categorized as having a low (0–3 points), medium (4–6 points), or high (7–9 points) level of evidence
  2. bN95 is a respiratory protective device designed to achieve a very close facial fit and very efficient filtration of airborne particles (i.e., droplets containing an infectious agent)
  3. c“Quantum” is a unit of measure that defines the amount of infectious material able to infect 1 − (1/e) (i.e., 63.2%) of the people in an enclosed space [21]