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

Patient Presentation
A 4-month-old female came to clinic for 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 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
Airplanesare a global transportation mechanism for the world for passengers and cargo. It is 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 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 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 (travel 60% alcohol) if not visibility dirty or if soap and water are not available.
Using sanitizer wipes of surfaces around food may also be helpful.
Minimizing exposures by keeping the air-conditioning nozzle on 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 seasonal influenza, country specific diseases and any outbreak diseases. Seeking advice from a travel clinic or a knowledgeable physician’s office with enough time to finish all the immunizations before traveling is important. Usually this is 4-6 weeks before traveling.
Some travel clinics may not provide pediatric care so some families may need to contact a local pediatrician.
Mask wearing in flight has been shown to decrease influenza 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

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What Health Risks Does Climate Change Pose?

Patient Presentation
A 9-month-old male came to clinic for his health supervision visit. His parents were graduate students at the local university and would be returning to live in China in 2 weeks. They were wondering about vaccines particularly for Japanese encephalitis because they would be living in a high risk area in China. The past medical history was unremarkable. The pertinent physical exam showed normal vital signs with growth parameters between 10-25% for height and weight and 50% for head circumference. The examination was otherwise unremarkable.

The diagnosis of a healthy male was made. The pediatrician discussed the options of starting the Japanese encephalitis vaccine in the U.S. and finishing it in China or waiting until they went to China to do the complete series there. “Japanese Encephalitis virus is more common during the warmer months, but I don’t know with the extent of climate change, if the risky time period has been extended,” the pediatrician said. Reviewing some governmental information with the parents on the computer in the room, the pediatrician was able to find out that there had been extension of the risk areas and time periods in East Asia. As it was April and the risk would be increasing, and after more discussion, the family decided to do the first Japanese Encephalitis vaccine in the U.S. and then followup with the second one once they were in China. The family felt good as this was similar to the routine Chinese vaccine schedule for infants also.

Discussion
Japanese encephalitis virus (JEV) is a Flavivirae, arbovirus that is endemic to many areas of Asia and the Pacific. It is estimated to affect ~70,000 people/year with ~10-15,000 deaths yearly in 20 countries, with a fatality rate of 35-40%. It can cause encephalitis and irreversible neurological morbidity. JEV is spread by Culex mosquitos which feed on swine. Increased environmental temperature and increased humidity (warm air is more moist) increases mosquito numbers, their survivability and ultimate dissemination. China has the highest rates of JEV with particular areas being more prone, as some areas co-farm rice and swine and the families live closely to the rice paddies and livestock which encourages transmission. JEV’s range has expanded over the past few decades including in 2009 into Tibet which was thought to be immune because of its altitude. Similar geographic spread has been found in other countries too such as Australia. Mass immunization in China and other countries has decreased the disease but it still remains a threat.

Learning Point
Weather is a moment-to-moment, day-to-day event and differs from climate which occurs across seasons, many years, and regions. “Climatic conditions and weather patterns have many consequences for human physiology, health and survival. Some health impacts, as from extreme exposures such as heat waves, occur directly. However, most climate-related health risks are mediated via the influences of climatic changes and shorter term weather fluctuations on food yields, water flows, patterns of infectious disease and the movement or displacement of groups and populations. When climatic conditions change over time, then we should expect changes in patterns of health risks and in population health profiles.” Most climatic health issues are not due to direct affects, but are due to indirect effects on the environment, ecology and social impacts.

Climate change health conditions include:

  • Primary/direct health effects
    • Are from extreme events such as heat waves, floods, fires, hurricanes/typhoons, landslides, tornados, and storms. The intensity and frequency of these events obviously can affect more people more frequently.
    • Direct health impact includes injuries, hospitalizations, poisoning, death, and numerous mental health issues. Children are especially affected by mental health issues.
  • Secondary health effects
    • Air quality related problems such as allergies and asthma
      • Air pollutants (including ground level ozone changes) and aeroallergens can increase because of wildfires, rising temperatures, rainfall patterns and altered crop yields.
    • Food related problems which can affect food supply, quality and overall nutrition
      • Rainfall patterns and soil temperature affects crop and animal food yields
      • Increased contamination of food/water with bacteria or environmental pollutants (including sewage) making food/water unusable
    • Infectious disease patterns
      • Expansion of number, range and activity of host species or vector species increases the infectious disease risks
      • Examples include non-human hosts of rodents, bats and vector-born illnesses such as Dengue, Hantavirus, Japanese Encephalitis Virus, Leishmaniasis, Lyme disease, malaria, schistosomiasis, and others.
  • Tertiary health effects
    • Water changes including stocks and flows of reservoir water such as groundwater recharging and glaciers/snowpack
    • Sea water elevation can cause local changes in water quality (increased bacterial or environmental toxins) with decreased fishing, arable or grazing land.
  • Changes in food and water supplies and land availability can lead to increased epidemics, population stress, conflict, population displacement and deteriorating social structure
    • “Displacement typically entails increased risks to health from undernutrition, infectious diseases, conflict situations, mental health problems – and from changes in health related behaviors such as alcohol consumption, tobacco smoking and transactional sex.”

On the potential positive side, some climatic changes can benefit some regions such as cold-weather areas will have fewer strokes or myocardial infarctions due to winter weather. Temperate areas that become even warmer could have drier conditions and therefore fewer mosquito-borne infectious diseases as there is less water for breeding and decreased lifespan.

Questions for Further Discussion
1. What climate change health conditions have you seen locally?
2. What climate change health conditions could you expect in your local area?

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 these topics: Climate Change, Environmental Health, and International 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.

Kurane I. The effect of global warming on infectious diseases. Osong Public Health Res Perspect. 2010 Dec;1(1):4-9.

McMichael AJ, Lindgren E. Climate change: present and future risks to health, and necessary responses. J Intern Med. 2011 Nov;270(5):401-13.

Bai L, Morton LC, Liu Q. Climate change and mosquito-borne diseases in China: a review. Global Health. 2013 Mar 9;9:10.

Tian HY, Bi P, Cazelles B, Zhou S, et.al.. How environmental conditions impact mosquito ecology and Japanese encephalitis: an eco-epidemiological approach. Environ Int. 2015 Jun;79:17-24.

Ahdoot S, Pacheco SE; Council on Environmental Health. Global Climate Change and Children’s Health. Pediatrics. 2015 Nov;136(5):e1468-84.

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