Lack of Airborne Transmission during Outbreak of Pandemic (H1N1) 2009 among Tour Group Members, China, June 2009

Abstract

This outbreak was caused by droplet transmission.

Influenza A(H1N1)pdm09 during air travel

“…Flights of longer duration, such as intercontinental flights, may pose a greater risk of transmission, particularly given greater potential for patients on longer flights to develop initial symptoms while on-board as has been found in other investigations. 9,11 However, other investigators who attempted contact investigations during the initial phase of the 2009 pandemic concluded that tracing close contacts among flight passengers was not effective, as timely provision of post-exposure prophylaxis could not be achieved in most cases. 37 Investigation of transmission of novel influenza strains aboard aircraft during the initial phases of an epidemic or pandemic may be instructive.…”

“…Though none were tested to confirm pH1N1 infection, these observations replicate published findings of travelers in groups, who are more likely to contribute to pH1N1 transmission than non-epidemiologically linked air travelers. 10,11 Limitations to this investigation included potential misclassification and recall bias regarding symptoms, dates of onset of illness, and aircraft seating location. In-cabin assessments of the association between illness and proximity to the index case were complicated by the lack of assigned seating on flights A1 and A2.…”

“…[5][6][7][8][9] Published studies of pH1N1 transmission among air travelers report that virus transmission during air travel is probable, but the risk of infection to susceptible passengers and crew may be limited, and the role of the aircraft cabin environment is unclear. [10][11][12] Documented risk factors associated with seasonal influenza virus transmission include receiving or providing health care 13 ; being in close quarters (e.g., in a household, daycare, or schools) with index patients 14 ; and close proximity to (within 1 m) or being in crowded or enclosed environments (including aircraft cabins) with an index patient who is coughing and sneezing. 9,15 To investigate the potential for person-to-person transmission of pH1N1 during air travel, the Centers for Disease Control and Prevention (CDC) conducted epidemiologic investigations among passengers who flew on flights with ill persons with laboratory-confirmed pH1N1.…”

Pandemic influenza A (H1N1) 2009: the experience of the first six months

“…However, one study found that pandemic H1N1/09 virus is transmitted less efficiently via respiratory droplets (16). Droplet transmission does appear to be effective in humans, as an outbreak of pandemic H1N1/09 among tourists in China was caused by talking with the index patient at close range (18).…”

Effective Containment of Pandemic Influenza (H1N1 2009) Virus Outbreak in an International Residence Hall of a University by Recommended Infection Control Guidance

“…The main route for influenza transmission is via large droplets. Transmission of influenza through the air over longer distances is thought not to occur (8,9). Although the postexposure antiviral prophylaxis was not given to any close contacts, no case occurred among the roommates.…”