Where is the Greatest Risk of Infectious Disease Transmission While Onboard an Airplane?

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Where is the Greatest Risk of Infectious Disease Transmission While Onboard an Airplane?

Patient Presentation
A 4-month-old female came to clinic for a health supervision visit. She was a former full-term infant with no problems pre- or post-natally. The family was leaving in 2 weeks to visit relatives in Africa for 6 weeks, and asked about precautions they should take during the flight. The parents were fully immunized except for seasonal influenza, and had not discussed their own health needs with their own physician.

The pertinent physical exam showed a smiling infant with weight and length parameters at the 25% and head circumference at the 50%.
Her examination was normal. The diagnosis of a healthy female was made. After reviewing the country specific vaccine recommendations from the Centers for Disease Control, the pediatrician recommended that the parents talk with their own physician about malaria prophylaxis and yellow fever vaccine. She also recommended that they receive seasonal influenza that could be given at the influenza clinic adjacent to the pediatric clinic after the visit. “There’s not much more you can do while on the airplane other than use the hand sanitizers a lot and turn on the overhead vent to circulate the air,” the pediatrician counseled. “Especially try to make sure you wash your hands before touching the baby,” he counseled. He also discussed other travel recommendations for clean water use and mosquito control while in the country. “Because of her age, if she gets sick we recommend she sees a doctor,” he advised them.

Discussion
Airplanes are a global transportation mechanism for the world for passengers and cargo. They are an engine which helps to fuel the global economy. In 2014, over 3.3 billion people traveled to more than 41,000 airports and 50,000 routes across the world. It is possible to travel around the world within about 24 hours. This is shorter than most infectious disease incubation periods. Although entry screening into countries is done, exit screening closer to the source is a better model as noted with the recent Ebola outbreak in west Africa in 2014.

Individual infectious disease risk includes the generation rate of the infectious disease, i.e. the source strength, the proximity and duration of the exposure, ventilation, and chance. Most commercial aircraft have cabin airflow that is designed to change over 10-15x/hour or more, with internal filtered and recirculated air progressively becoming diluted with incoming external air. The ventilation is designed to flow from side-to-side of the aircraft and not down the long axis of the fuselage. High efficiency particulate arrestance (HEPA) air filters are used which can capture up to 99.97% of 0.1-0.3 micrometer particulate and 100% of larger particles. HEPA filters are not required nor regulated in the US and Europe. The environmental control system is also designed to mitigate external contaminants into the cabin though.

Infectious diseases can be transmitted by airborne particulates, large droplets which settle on surfaces (60% alcohol) if not visibly dirty or if soap and water are not available. Using sanitzer wipes of surfaces around food may also be helpful. Minimizing exposures by keeping the air conditioning nozzle on at a low setting, not sitting in the window seat during the winter season and sitting near the front of the aircraft can help. People traveling should be current with routine vaccination including country specific diseases. Travel clinic or a knowledgeable physicians office with enough time to finish before traveling is important. Usually this is 4 to 6 weeks before traveling. Some travel clinics may not provide Pediatric local pediatrician. Mask wearing in-flight has also been shown to decrease the acquisition but is often not practical especially on long flights.

Learning Point
The overall risk of infectious diseases being spread on board during airline travel is small but does occur. According to Mangili, Vindes and Gendreau in 2015: “Current risk assessment protocols used by public health authorities for inflight infectious disease exposures are typically based upon the proximity of the fellow passenger to the index passenger, sitting within two rows of the index passenger and the duration of the exposure, exemplified by studies of transmission of Mycobacterium tuberculosis on board and air flight which is limited to close contacts and a flight time of greater than eight hours. This protocol is based upon experiences with previous tuberculous exposures/outbreaks aboard commercial flights and has become conventional wisdom for investigating most aircraft related infectious disease and incidences.” These authors note that this protocol does not consider ventilation, an infectious disease key modifier, and there are other mathematical formulas which might be more accurate.

Questions for Further Discussion
1. What infectious diseases are potentially spread by air travel?
2. What routine travel instructions do you provide to families?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Traveler’s Health

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

To view videos related to this topic check YouTube Videos.

Pavia AT. Germs on a plane: aircraft, international travel, and the global spread of disease. J Infect Dis. 2007 Mar 1;195(5):621-2.
European Centre for Disease Prevention and Control. Risk assessment guidelines for infectious diseases transmitted on aircraft. Available from the Internet at http://ecdc.europa.eu/en/publications/Publications/0906_TER_Risk_Assessment_Guidelines_for_Infectious_Diseases_Transmitted_on_Aircraft.pdf (2009, cited 1/17/17).

Bogoch II, Creatore MI, Cetron MS, et.al.. Assessment of the potential for international dissemination of Ebola virus via commercial air travel during the 2014 west African outbreak. Lancet. 2015 Jan 3;385(9962):29-35.

Centers for Disease Control. Conveyance and Transportation Issues: Air Travel. Yellow Book. Available from the Internet at https://wwwnc.cdc.gov/travel/yellowbook/2016/conveyance-transportation-issues/air-travel (rev. 7/10/15, cited 1/17/17).

Mangili A, Vindenes T, Gendreau M. Infectious Risks of Air Travel. Microbiol Spectr. 2015 Oct;3(5).

World Health Organization. Transmission of communicable diseases on aircraft. Available from the Internet at http://www.who.int/ith/mode_of_travel/tcd_aircraft/en/ (cited 1/17/17).

Author
Donna M. D’Alessandro, MD
Professor of Pediatrics, University of Iowa Children’s Hospital

Date
March 20, 2017

Question and Answer

The highest risk of an infectious disease transmission on board an aircraft is within how many rows of an index case?

A. 0, same row as passenger
B. 1 row
C. 2 rows
D. 4 rows
E. 6 rows

Answer: C

The overall risk of infectious diseases being spread on board during airline travel is small but does occur.
According to Mangili, Vindes and Gendreau in 2015:
“Current risk assessment protocols used by public health authorities for inflight infectious disease exposures are typically based upon the proximity of the fellow passenger to the index passenger, sitting within two rows of the index passenger and the duration of the exposure, exemplified by studies of transmission of Mycobacterium tuberculosis on board and air flight which is limited to close contacts and a flight time of greater than eight hours. This protocol is based upon experiences with previous tuberculous exposures/outbreaks aboard commercial flights and has become conventional wisdom for investigating most aircraft related infectious disease and incidences.”
These authors note that this protocol does not consider ventilation, an infectious disease key modifier, and there are other mathematical formulas which might be more accurate.

To review the entire case, see Where is the Greatest Risk of Infectious Disease Transmission While Onboard an Airplane?

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