Germs on a plane: Can you get sick flying?

Dr. Judith Reichman 'Today' show contributor • Profile • E-mail

“Snakes on a Plane” was an intriguing movie title. “Microbes on a Plane” sounds more realistic and raises a common fear of colds, flu or worse. Here on “Today’s Woman”, our medical contributor, Dr. Judith Reichman, will help us understand if and why we are at risk for infections as we join the over one billion passengers who travel by air every year. Dr. Reichman answers some common questions:

Why do those who fly frequently complain of headache, fatigue, fever or breathing problems?
Some of these symptoms may be due to the low barometric pressure, oxygen content and humidity in the air cabin. When combined with jet lag, sleep deprivation, stress, (security concerns, long lines, missed flights, delayed and cancelled flights), as well as cramped seating, motion sickness and discomfort from vibration and engine noise, we have ample reason to feel “ill.” And let’s not forget that engine fumes can, on occasion, seep into the cabin.

While acknowledging all these factors, we also should consider whether infections can occur as a result of air water or food contamination and whether there is a risk of “catching something” from other passengers in the confined environment on the aircraft.

Is the closed environment of an airplane a repository for germs?
Not necessarily. In order to address the “is a plane a moving culture for viruses and bacteria” question, we have to understand how the aircraft cabin is ventilated. Once in flight, the air from the outside (which should be sterile at higher altitudes) is vented through the engines where it is heated, compressed and subsequently cooled. It then flows into the plane from overhead air vents, circulates across the aircraft and exits from the floor of the cabin. The airflow is laminar, i.e. side-to-side. This means it flows from top to bottom in lateral sections, not from front to back. Usually about 50% of the air is re-circulated, and as this happens, it passes through very special air filters, which remove dust, vapors, bacteria, and mold. Although a virus would be too small to be trapped by the filter, we know that viruses are usually attached (or spread by) droplets. And these are removed by the filters.

The air is usually exchanged at a rate of 15 to 20 air changes per hour, (compared to 12 air changes per hour in a typical office building). As a matter of fact, in a recent report to the House Subcommittee on Aviation, experts stated that “data from epidemiologic studies and microbiologic assays indicate that the risk of airborne infections currently appears to be very low.” And an independent published research showed that the concentration of biological microorganisms in planes is lower than in an office building, an ordinary city street and on public buses or trains.

So is there an infection risk for passengers?
Even if the air is appropriately circulated there are however, ways that infections can be transmitted to passengers:

• Contact infection. This occurs from body-to-body contact or from large droplets that are sprayed several feet when an infected person sneezes, coughs or talks. The virus or bacteria sprayed at you then enters your body and infects you through your eyes, nose or mouth.
• Airborne infection. This occurs when larger infected droplets partially evaporate. The residue or smaller droplets becomes widely dispersed in the air and remains there until the air is exchanged or appropriately filtered.
• Vehicle transmission. The microorganism is spread through infected food and water.
• Vector-borne transmission. Diseases (such as malaria) are spread through insect bites and vermin.
• The first two modes of transmission will account for the greatest risk of infection. That risk, however, is dependent on how infectious the “sick” person is, the proximity of his seat, and duration of the exposure. (Flights over eight hours appear to be of greatest risk).

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