Calculating the potential for within-flight transmission of influenza A (H1N1)

Center for Biomedical Modelling, Semel Institute of Neuroscience and Human Behavior, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
BMC Medicine (Impact Factor: 7.25). 12/2009; 7(1):81. DOI: 10.1186/1741-7015-7-81
Source: PubMed


Clearly air travel, by transporting infectious individuals from one geographic location to another, significantly affects the rate of spread of influenza A (H1N1). However, the possibility of within-flight transmission of H1N1 has not been evaluated; although it is known that smallpox, measles, tuberculosis, SARS and seasonal influenza can be transmitted during commercial flights. Here we present the first quantitative risk assessment to assess the potential for within-flight transmission of H1N1.
We model airborne transmission of infectious viral particles of H1N1 within a Boeing 747 using methodology from the field of quantitative microbial risk assessment.
The risk of catching H1N1 will essentially be confined to passengers travelling in the same cabin as the source case. Not surprisingly, we find that the longer the flight the greater the number of infections that can be expected. We calculate that H1N1, even during long flights, poses a low to moderate within-flight transmission risk if the source case travels First Class. Specifically, 0-1 infections could occur during a 5 hour flight, 1-3 during an 11 hour flight and 2-5 during a 17 hour flight. However, within-flight transmission could be significant, particularly during long flights, if the source case travels in Economy Class. Specifically, two to five infections could occur during a 5 hour flight, 5-10 during an 11 hour flight and 7-17 during a 17 hour flight. If the aircraft is only partially loaded, under certain conditions more infections could occur in First Class than in Economy Class. During a 17 hour flight, a greater number of infections would occur in First Class than in Economy if the First Class Cabin is fully occupied, but Economy class is less than 30% full.
Our results provide insights into the potential utility of air travel restrictions on controlling influenza pandemics in the winter of 2009/2010. They show travel by one infectious individual, rather than causing a single outbreak of H1N1, could cause several simultaneous outbreaks. These results imply that, during a pandemic, quarantining passengers who travel in Economy on long-haul flights could potentially be an important control strategy. Notably, our results show that quarantining passengers who travel First Class would be unlikely to be an effective control strategy.

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Available from: Sally Blower, Feb 28, 2014
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    • "Previous studies have concluded that the net benefits to society of air travel restrictions are at best small [11]–[13], but most models rely on assumptions that have not been confronted with data [14]. What does seem clear is that flying increases the likelihood of air travelers contracting an infectious disease conditional on there being on infectious person on the airplane [15], [16], and that the public links flying with infection risk. Air travel may increase private infection risk beyond an acceptable level, and public health interventions related to travel and airport surveillance programs may benefit travelers [17], [18]. "
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    • "After the passengers departed the aircraft, subsequent exposure measurement became inefficient and difficult (Baker et al., 2010). Thus, in-flight measurement of the potential risks of H1N1 transmission was proposed (Wagner et al., 2009). As an efficient means for spreading infectious diseases, air transport is also of concern regarding its influence on risks of transmission of other infectious diseases, including tuberculosis (Abubakar, 2010; Dowdall et al., 2010; Kornylo-Duong et al., 2010), malaria (Bradley, 1989; Tatem et al., 2006), plague (Pascali, 1982), yellow fever (Oliva, 1979), cholera (Rondle et al., 1978), dengue fever, Norwalk virus (Kirking et al., 2010), and epidemic meningococcal diseases (Rachael et al., 2009). "
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    • "Yet, the simple combination of the previous models will not generate what is needed because they focus on contacts (people or animals) and, at the earliest epidemic phase, the number of infected individuals is very low. While air-borne epidemics have been investigated [12], [37], they are atypical because their connecting structure is mobile, and, in air travel-mediated epidemics, reduced to the few yards that separate passengers sharing the same aircraft. "
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