Airplanes

Airplane travel will make you sick

Rachel spends half of the year doing research and caring for children with HIV in Kenya. Going back and forth to Africa several times a year means a lot of time on airplanes (and a lot of frequent flier miles). Does it also mean that Rachel has a lot of extra colds? Rachel’s family is convinced that she is always coming off airplane flights with some sort of sickness. If Airborne is not going to protect her on the plane, is she doomed to exposure to one germ after another?

Many people are convinced that airplanes are guaranteed incubators for coughs and colds. Vice President Joe Biden once warned family members that they should avoid airplanes during the time of the swine flu epidemic because a single sneeze in the confined space of a plane could go “all the way through the aircraft.” The makers of Airborne particularly recommend taking their herbal supplement before you fly on a plane in order to prevent colds. One has to wonder just how significant the health risks are when you fly.

It is easy to imagine how airplanes could be incubators for illness. Airplanes are confined spaces, and they have limited ventilation. People worry that the airplane ventilation systems may recirculate stale cabin air. Plus, if you have a long flight, you may be close to a sick person for a relatively long time.

Studies have found some evidence that traveling on a plane can lead to infections among other air travelers. Studies looking at the transmission of pandemic A/H1N1 influenza (swine flu) in 2009 did show an increased chance of getting swine flu if you were in close proximity to a passenger on an airplane who was already infected. For swine flu, the risk was only increased for those people within two rows of the sick passengers. There are also case reports of diseases such as tuberculosis, measles, and other types of influenza being transmitted from one passenger on a plane to another. We have to admit that air travel can be a risk. (This is also a good reminder to get vaccinated against whatever infections you can since you never know what the person next to you on a plane might have.)

Before you cancel your next flight, though, you should look at the big picture. Air travel is not nearly as risky as it may sound. Bugs and viruses are actually spread during flight very rarely. You put yourself at risk for getting an infection whenever you go out in public. Studies show that you have no more risk of getting sick after being on an airplane than you do if you spend the same amount of time on trains, buses, or in buildings like offices or malls. Airplanes are not the worst culprits. In fact, one study found lower levels of bacteria and fungi in airplanes than in buses, malls, or even in the outside air! Studies that look at cultures from airplanes show very low levels of growing bacteria or viruses. Airplanes have a number of factors in their favor that help to keep them much healthier than you might imagine.

First of all, the air in the cabin of an airplane is really quite clean. The cabin air originally comes from the air outside the plane, which is at very high altitude. High altitude air starts off with very few bacteria and viruses in it. Then, the air is compressed and heated before it gets sent into the cabin, a process that should also kill remaining bacteria or viruses. So the air that comes into the airplane for you to breathe is actually very clean. Of course, the next step is for that clean air to start recirculating in a cabin that may include sick people. Some risk enters the picture with the recirculation, but the risk is really very low. Within an airplane’s recirculation system, the air is filtered through a system of high efficiency particulate air (HEPA)–type filters. These filters are very good at removing bacteria and even viruses from the air; they are better than the filters in most buildings, and are the same kinds of filters used to clean the air in hospital wards or operating rooms. Therefore, both the air coming into the plane from outside and the recirculated air once inside are very clean overall.

To make the ride in the plane even safer, the air in the cabin is exchanged very frequently, typically twenty times in an hour. This is much better than most office buildings, where air is exchanged twelve times in an hour, or most houses, where air is exchanged five times in an hour. The air circulation system also tries to avoid sending the air all around the plane. Instead, the air that leaves from a particular row, after being cleaned, comes back to that particular row. The air exchange moves from the top to the bottom of the plane, rather than from the front to the back. If any germs manage to get into the air, they stay pretty close to the infected person, instead of traveling all through the plane. The current airplane recirculation systems seem to work pretty well. In fact, in a study of airplane air circulation, there was no difference in how many respiratory symptoms passengers developed if they were on a plane that recirculated air compared to a plane that had no recirculation and only used new air from outside.

But perhaps you’ve felt ill in other ways after you’ve flown. While the plane may not be a dangerous incubator for colds, there are some other ways in which flying might affect you. While it’s quite clean, the air on the plane is also very dry. This actually helps prevent infections because bacteria and viruses like to live in tiny water droplets in more humid air, but the dry air might make your nose and throat dry too. Having a dry nose and throat could lead to bothersome irritation of your sinuses and respiratory system. Some researchers speculate that dry, irritated mucus membranes might make it easier for you to get infected with a cold later on, but this has not been proven.

Traveling on long flights in an airplane can also put you at risk for developing a blood clot in your leg (called a deep vein thrombosis or DVT). DVT can result from long periods of time where you have to sit still or are not able to move as much, such as being in bed after surgery or sitting still on a long airplane ride. Flexing your legs frequently and walking around when you can on a long plane ride are smart ways to try to prevent developing DVT.

There have also been cases where people on a particular flight later developed diarrhea and vomiting after one passenger had been very sick in the airplane bathroom. Unfortunately, contamination of the bathroom and subsequent poor hand-washing by others caused this infection to spread. You can imagine how gross that bathroom must have been! Contaminated bathrooms anywhere can cause infections to spread, so wash your hands and try not to touch obviously dirty stuff.

So, as it turns out, airplanes are not so icky after all. People worry about the quality of air in airplanes and about how likely they are to get sick from their time on the plane, but the studies of airplane ventilation systems and of who gets sick after air travel both suggest that we are a lot more worried than we need to be. Although it is possible to have infections pass among passengers on airplanes, there are many precautions in place that help make this a low risk. The heating of almost sterile outside air, the filtration systems, the low humidity, and the patterns of airflow in the plane all minimize the chance of spreading infections among passengers. Even for frequent fliers, the risk of being on a plane does not seem to be any greater than the risk of being on a train or bus or even the risk from going to the office.