A new study examines that passengers transmitting infectious diseases to one another is low, new data suggest. Although passengers seated in one row or two seats on either side of an infected individual have an 80% or higher chance of becoming infected, the likelihood was less than 3% for the remaining passengers. The study was published in the Proceedings of the National Academy of Sciences.

Transmission is limited to one row in front of or behind an infectious passenger. This is more conservative than current public health guidance, calling for surveillance of passengers within two rows of an infectious passenger. More than a dozen documented cases of in-flight transmission have occurred.

A research on severe acute respiratory syndrome (SARS) and pandemic influenza (H1N1p) transmission on airplanes shows that air travel can help newly emerging infections and pandemics spread rapidly. To estimate the risk, the 10-member research team flew on 10 transcontinental flights that lasted between 211 and 313 minutes.

Of those flights, seven had no unoccupied seats and the other flights had two, three, and 17 unoccupied seats. The researchers observed and recorded the actions and movements of 1540 passengers seated and 41 crew members working in the economy class cabin of single-aisle airplanes.

Infection Transmission Closely Linked to Movement of Passengers and Crew

Estimated infection transmission was closely linked to the movement of passengers in the airplane, and the extent to which passengers moved varied according to where they were seated. More than one third (38%) of passengers remained in their seats for the duration of the flight, 38% left once, 13% left twice, and 11% left more than twice.

Only half of the passengers visited a lavatory during the flight: 38% used it once, 9% used it twice, and 3% used it more than twice. For passengers, the most frequent behaviors were waiting for, using, or leaving a lavatory (825 passengers; average time, 4.3 minutes) and checking the overhead storage bin (135 passengers; average time, 1 minute).

Of the 1296 passengers (84%) who had close contact with a passenger sitting beyond a 1-m radius from them because of movement, the median number of contacts was 44, and the median total duration of that contact was 47 person-minutes. For each individual contact, the median duration was 0.4 minutes.

The authors say their findings should not be extrapolated to short-hop domestic flights, international flights on other airlines. Passengers on short-hop flights may move around less, and those on longer international flights may move much more.

Researchers conclude that the results also cannot be extrapolated from single-aisle cabins to double-aisle cabins commonly used for international flights. Different airlines will have different cabin-disinfection protocols and supervise their cabin-cleaning staff in different ways.