Worldwide, >2.8 billion people travel by commercial aircraft every year, and this number continues to rise. Travelers often have concerns about the health risks of flying in airplanes. Those with underlying illness need to be aware that the entire point-to-point travel experience, including buses, trains, taxis, public waiting areas, and even movement within the airport, can pose challenges. Although illness may occur as a direct result of air travel, it is uncommon; the main concerns are:
- Exacerbations of chronic medical problems due to changes in air pressure and humidity
- Relative immobility during flights (risk of thromboembolic disease, see Chapter 2, Deep Vein Thrombosis & Pulmonary Embolism)
- Close proximity to other passengers with certain communicable diseases.
Preflight Medical Considerations
During flight, the aircraft cabin pressure is usually maintained at the equivalent of 6,000–8,000 ft (1,829–2,438 m) above sea level. Most healthy travelers will not notice any effects. However, for travelers with cardiopulmonary diseases (especially those who normally require supplemental oxygen), cerebrovascular disease, anemia, or sickle cell disease, conditions in an aircraft can exacerbate underlying medical conditions. Aircraft cabin air is typically dry, usually 10%–20% humidity, which can cause dryness of the mucous membranes of the eyes and airways.
The new Boeing 787 and Airbus A 350 boast innovative changes: a greater number of temperature zones, a higher humidity of 25%, a faster time to refresh cabin air, lower ambient noise, and multiple shades of LED lighting. These, along with a cabin air pressure equivalent to an altitude of only 2,000 ft, promise to insure greater comfort and ease jet lag.
The Aerospace Medical Association (www.asma.org) recommends evaluating chronic medical conditions and addressing instabilities prior to travel, particularly in those who have underlying cardiovascular disease, a history of deep venous thrombosis or pulmonary embolism, chronic lung disease, surgical conditions, seizures, stroke, mental illness, and diabetes.
For information on contraindications and precautions related to flying during pregnancy, see Chapter 8, Pregnant Travelers. Specific information for travelers with disabilities and medical conditions that may affect security screening can be found at www.tsa.gov/travel/special-procedures. For those who require supplemental in-flight oxygen, the following must be taken into consideration:
- Travelers must arrange their own oxygen supplies while on the ground, at departure, during layovers, and upon arrival.
- Federal regulations prohibit airlines from allowing passengers to bring their own oxygen onboard; passengers requiring in-flight supplemental oxygen should notify the airline ≥72 hours before departure.
- Airlines might not offer in-flight supplemental oxygen on all aircraft or flights; some airlines permit only Federal Aviation Administration (FAA)-approved portable oxygen concentrators. Information to assist people who require supplemental oxygen during travel and FAA-approved portable oxygen concentrators can be found at the FAA website: www.faa.gov/about/initiatives/cabin_safety/portable_oxygen.
- Information regarding the screening of portable oxygen concentrators at airports in the United States can be found at www.tsa.gov/node/1754.
For more information, see Chapter 8, Travelers with Chronic Illnesses.
Barotrauma during Flight
Barotrauma may occur when the pressure inside an air-filled, enclosed body space (such as the middle ear, sinuses, or abdomen) is not the same as the air pressure inside the aircraft cabin. It most commonly occurs during rapid changes in environmental pressure, such as during ascent, when cabin pressure rapidly decreases, and during descent, when cabin pressure rapidly increases. Barotrauma most commonly affects the middle ear; it occurs when the eustachian tube is blocked and thus unable to equalize the air pressure in the middle ear with the outside cabin pressure. Middle ear barotrauma is usually not severe or dangerous and can usually be prevented or self-treated. It may rarely cause complications such as a perforated tympanic membrane, dizziness, permanent tinnitus, or hearing loss. The following suggestions may help avoid potential barotrauma:
- People with ear, nose, and sinus infections or severe congestion may wish to temporarily avoid flying to prevent pain or injury.
- Oral or nasal decongestants may alleviate symptoms.
- Travelers with allergies should continue their regular allergy medications.
- Travelers should stay hydrated to help avoid irritation of nasal passages and pharynx and to promote better function of the eustachian tubes.
- Travelers sensitive to abdominal bloating should avoid carbonated beverages and foods that can increase gas production.
- People who have had recent surgery, particularly intra-abdominal, neurologic, intrapulmonary, or intraocular procedures, should consult with their physicians before flying.
Ventilation and Air Quality
All commercial jet aircraft built after the late 1980s, and a few modified older aircraft, recirculate 10%–50% of the air in the cabin, mixed with outside air. The recirculated air passes through a series of filters 20–30 times per hour. In most newer-model airplanes, the recycled air passes through high-efficiency particulate air (HEPA) filters, which capture 99.9% of particles (bacteria, fungi, and larger viruses or virus clumps) 0.1–0.3 µm in diameter. Furthermore, air generally circulates in defined areas within the aircraft, thus limiting the distribution of pathogens spread by small-particle aerosols beyond a small number of rows. As a result, the cabin air environment is not conducive to the spread of most infectious diseases.
Some diseases may be spread by contact with infected secretions, such as when an ill person sneezes or coughs and the secretions or droplets land on someone’s face (mouth, nose, eyes), or by touching a contaminated surface and then touching one’s face with contaminated hands. Practicing good handwashing and respiratory hygiene (covering mouth when coughing or sneezing) decreases the risk of disease spread by direct or indirect contact.
In-Flight Medical Emergencies
The increasing number of travelers combined with an aging flying population make the incidence of onboard medical emergencies likely to increase. Medical emergencies occur in approximately 1 in 600 flights; this is approximately 16 medical emergencies per 1 million passengers. The most commonly encountered in-flight medical events are:
- Syncope or presyncope (37%)
- Respiratory symptoms (12%)
- Nausea or vomiting (10%)
- Cardiac symptoms (8%)
- Seizures (6%)
Although in-flight medical emergencies occur, serious illness or death onboard a commercial aircraft is rare. Deaths onboard commercial aircraft have been estimated at 0.3 per 1 million passengers; approximately two-thirds of these are caused by cardiac conditions. Most commercial airplanes that fly within the United States are required to carry at least 1 approved automatic external defibrillator (AED) and an emergency medical kit.
Flight attendants are trained in basic first aid procedures such as CPR, and use of AED machines but are generally not certified in emergency medical response. Many airlines use ground-based medical consultants to assist flight crew and volunteer passenger responders in managing medical cases. In nearly one-half of in-flight emergencies, physician volunteers have provided assistance. The Aviation Medical Assistance Act, passed in 1998, provides some protection from liability to providers who respond to in-flight medical emergencies.
The goal of managing in-flight medical emergencies is to stabilize the passenger until ground-based medical care can safely be reached. When considering diversion to a closer airport, the captain must consider the needs of the ill passenger, as well as other safety concerns such as weather, landing conditions, and terrain. Certain routes, such as transoceanic flights, and availability of definitive medical care may restrict diversion options.
In-Flight Transmission of Communicable Diseases
Communicable diseases may be transmitted to other travelers during air travel; therefore, people who are acutely ill, or still within the infectious period for a specific disease, should delay their travel until they are no longer contagious. For example, otherwise healthy adults can transmit influenza to others for 5–7 days. Travelers should be up-to-date on routine vaccinations and receive destination-specific vaccinations before travel. Travelers should be reminded to wash their hands frequently and thoroughly (or use an alcohol-based hand sanitizer containing ≥60% alcohol), especially after using the toilet and before preparing or eating food, and to cover their noses and mouths when coughing or sneezing.
Aircraft contact investigations may be conducted for certain serious communicable diseases (see CDC’s webpage “Protecting Travelers’ Health from Airport to Community: Investigating Contagious Diseases on Flights” at www.cdc.gov/quarantine/contact-investigation.html). If a passenger with a serious communicable disease was infectious during a flight, passengers who may have been exposed may be contacted by public health authorities for possible screening or prophylaxis. When necessary, public health authorities will obtain contact information from the airline for potentially exposed travelers so they may be contacted and offered an intervention.
For information regarding CDC’s travel restrictions, see www.cdc.gov/quarantine/qas-frn-travel-restriction.html. To request a consultation, public health authorities may contact the CDC quarantine station of jurisdiction (see www.cdc.gov/quarantine/quarantinestationcontactlistfull.html) or the CDC Emergency Operations Center by calling 770-488-7100.
Tuberculosis (Mycobacterium tuberculosis )
Tuberculosis (TB) is transmitted from person to person via airborne respiratory droplet nuclei. Although the risk of transmission onboard aircraft is low, CDC recommends conducting passenger contact investigations for flights ≥8 hours if the person with TB has sputum that is smear-positive for acid-fast bacilli and cavitation on chest radiograph or has multidrug-resistant TB. People known to have active TB disease should not travel by commercial air (or any other commercial means) until they are determined to be noninfectious. State health department TB controllers are valuable resources for advice to determine when a person can be considered noninfectious (www.tbcontrollers.org/community/statecityterritory).
Meningococcal disease (Neisseria meningitidis )
Meningococcal disease caused by N. meningitidis is transmitted by direct contact with respiratory droplets and secretions and can be rapidly fatal. Therefore, close contacts of ill travelers need to be quickly identified and provided with prophylactic antimicrobial agents. Antimicrobial prophylaxis should be considered for any of the following:
- Household members traveling with the ill traveler
- Travel companions with prolonged close contact
- Travelers seated directly next to the ill traveler on flights ≥8 hours (gate to gate) or who have had direct contact with respiratory secretions or vomitus.
Measles is a viral illness transmitted by respiratory droplets, direct contact, or airborne routes. Most measles cases diagnosed in the United States are imported from countries where measles is endemic. An ill traveler is considered infectious during a flight of any duration if he or she traveled during the 4 days before rash onset through 4 days after rash onset. Flight-related contact investigations are initiated as quickly as possible so postexposure prophylaxis may be provided to susceptible travelers. If indicated, MMR (measles, mumps, and rubella) vaccine given within 72 hours of exposure or immune globulin, given within 6 days of exposure, may prevent measles or decrease its severity in people who are not immune.
To reduce the accidental spread of mosquitoes and other vectors via airline cabins and luggage compartments, a number of countries require disinsection of all inbound flights or flights from certain areas. Although disinsection, when done appropriately, was declared safe by the World Health Organization (WHO) in 1995, there is still much debate about the safety of the agents and the effectiveness of disinsection as a public health measure to prevent the spread of vectorborne diseases. Although CDC reserves the right to require disinsection to control importation and spread of a vectorborne infectious disease, it is not currently required for aircraft arriving at US airports. WHO information on aircraft disinsection, including available procedures, can be found at www.who.int/ith/mode_of_travel/aircraft_disinsection/en. An updated list of countries that require disinsection, and the types of methods used, is available at the Department of Transportation website: www.transportation.gov/office-policy/aviation-policy/aircraft-disinsection-requirements.
Information For Air Crew
In preparation for a healthy journey, flight crew can refer to Chapter 8, Advice for Air Crews and to the CDC Travelers’ Health website (www.cdc.gov/travel). If flight crew encounter passengers with potentially infectious diseases, see the CDC Airline Guidance webpage: www.cdc.gov/quarantine/air. Requirements and tools for reporting are also provided.
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Susan A. Lippold, Tina Objio, Phyllis E. Kozarsky