Aerosol influenza transmission risk contours: A study of humid tropics versus winter temperate zone

Table 2 Risk of transmission during deplaning

	25%_G7 transmission risk contour line		40%_G7 transmission risk contour line		60%_G7 transmission risk contour line
	Per passenger	Per aircraft	Per passenger	Per aircraft	Per passenger	Per aircraft
Mean airplane deplane period 5 min
Range: 2 to 13 min	1/3917	1/20	1/2448	1/12	1/1632	1/8

Shows risk of contagion during the deplaning period of a flight, assuming an infected passenger shedding virus, assuming 200 passengers per aircraft. During deplaning, 22 of 87 time intervals of 2 minutes were above the 25%_G7 transmission risk contour, and 5 of 87 intervals were below the 60%_G7 contour. Deplaning mean contour was approximately 40%_G7. Moser[34] has a time period of 4.5 hours in an unventilated enclosed aircraft on March 14, 1977 in Homer, Alaska when the outdoor high was 0°C (outdoor RH ranged from 67% to 96%) while the aircraft sat on the runway with the ventilation off. In that incident, 39 of 54 passengers (72%) were reported ill from an index case. Using Equation 2 with 100%_G7 transmission risk, approximately 3 new infections would be expected, or roughly 10% of what was seen, which is a reasonable correlation given an enclosed space without ventilation and uncertainties about conditions. As others have noted, this confirms that factors such as ventilation have a strong impact on aerosol transmission[50]. Aerosol infectious virus load per unit of air would be expected to vary based on rate of input, rate of deactivation, and degree of dilution by ventilation. We think it is reasonable to include a multiplier on estimates where air exchange is poor and that 10× is a reasonable upper bound.

ISSN: 1743-422X