Do you have to worry about airborne disease on an international air flight?

Question

Flu? Pneumonia? Anthrax? smallpox? Do you have to worry about them or there are designs in place to prevent them? Like some sort of sophisticated ventilation system?

Models to work with: Most common ones: Boeing 737, Airbus A320

Answer 1

I'm afraid you're probably not going to like the answer! And really, the model makes little or no difference.

The MITRE Corporation did some studies on this and a good summary can be found in the article Detecting Aircraft Pathogens Before It's Too Late

The summary points are

the researchers determined that most particles stayed suspended in the aisle, so when booking a trip, take a window seat

and

Particles also did not travel far outside the contaminated row, and if they did, it was across the row. Previously, it was thought that contaminants would travel front to back, or back to front.

Most worryingly:

The need for such sensors was evident in the 2003 outbreak of Severe Acute Respiratory Syndrome (SARS), which originated in an Air China flight from Hong Kong to Beijing, spread through 18 countries, and resulted in 774 fatalities. Asian economies suffered $11 billion in damages

As for controlling pathogens on board an aircraft, the CDC provide guidance which involves the same procedures you'd use on the ground (Hand washing, PPE, handling of bodily fluids).

Although air is no doubt filtered, as far as I know there is nothing special about the filters used on Aircraft that would be unique to aviation, nor offer any additional defense against airborne pathogens.

Answer 2

No, not more than about catching a bug at any populated and air conditioned space. Some of the air in the cockpit is recirculated and before it re-enters the cockpit, it is filtered through HEPA filters. From this document:

The vast majority of U.S. airliners use high-efficiency particulate air (HEPA) recirculation filters for cabin air, and these filters are highly effective at collection of solid and liquid particulates.

These filters can remove 99.97% of particles up to 0.3 µm, as defined by MIL-STD-282 Method 102.9.1. Bacterial and viral particles are smaller, but the size of 0.3 µm is chosen because it is the hardest one to filter, smaller particles are caught in the HEPAs with a high rate (up to 98%) as well. In hospitals the filters are used together with strong ultraviolet light to kill the bacteria could by the filters.

Notice that the document above mentions that most US airlines use HEPA, which implies that filtering practices are airline dependent and not prescribed by FAA. The advise seems to be: fly a reputable airline.

Do you have to worry about bacteria and viruses on board of aircraft? If you're truly worried, wear a mask:

Though it’s inconclusive whether masks can block airborne viruses, “one thing we learned from the literature that we looked at is that if the healthy person is wearing a mask and walks into a sickroom and touches infected surfaces, the mask makes it hard to touch his or her own nose and mouth,” says Finkelstein, who is also an associate professor at Harvard Medical School.