Each year, an estimated 600 million passengers fly in the United States, and of those, roughly 350,000 are international travelers, according to the Bureau of Transportation Statistics. This leaves commercial airliners vulnerable to biological contamination and makes the spread of disease a real threat.
Now researchers at the MITRE Corporation have conducted a study that, for the first time, looks at the particle distribution of exhaled breath to better understand how airborne pathogens spread in aircraft cabins, and how best to detect the particles that could contain viruses.
“The most important point is that if you want to detect infectious viruses from exhaled breath, you need a biosensor with single particle detection,” says Grace Hwang, principal investigator of the study and a lead biosensors scientist at MITRE. “Most commercially available biosensors need 10 million viruses before they can inform the user that a virus of concern has been caught, and usually diagnosis takes three to four hours.” This is problematic, adds Hwang, since most viruses are found in low concentrations when expelled from an infected person, and many flights do not last more than 90 minutes.
In addition, the researchers determined that most particles stayed suspended in the aisle, so when booking a trip, take a window seat, says Michael Harkin, a member of the MITRE team, who presented the research at the 2009 IEEE Conference on Technologies for Homeland Security. 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. “There was minimal exposure to the row in front of, and to the window passengers in, [the contaminated row],” says Harkin. Thus, the researchers concluded that biosensors should be placed at the ceiling of the aircraft cabin, about every four rows.
“Our goal is to capture the infected cases coming into the U.S. before people are symptomatic,” says Hwang. “That will buy time to defend against a pandemic spread, and the economic benefits would be enormous.”
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. “If you have an appropriate device to detect pathogens on aircraft, which is a huge challenge, then you are prepared for a deadly outbreak,” says Byron Jones, associate dean for research and graduate programs at Kansas State University, and director of its engineering experiment station. “We have seen how the swine flu spreads, and while it has turned out to be a mild disease, if it were something deadly and contagious like typhoid fever, it could be a different story.” Jones is also part of a team of experts at the Air Transportation Center for Excellence currently looking into the healthfulness of aircrafts.
The first case of H1N1 occurred in April, and since then, there have been close to 80,000 flights within North America and only one air-travel case under investigation. The risk of catching H1N1 via airliners is low but present, adds Mark Gendreau, a senior staff physician and vice chair of emergency medicine at Lahey Clinic, in Burlington, MA, and an associate professor of emergency medicine at Tufts University School of Medicine, in Boston.