My wife and I just got back from Alaska on August 10, 2015 and within a few days became progressively symptomatic with an influenza-like illness that appears to be peaking today on day 5. I know exactly how we were infected. There were several ill passengers, particularly in close proximity who had not mastered coughing into the crook of the arm and who were actually coughing and sneezing over the top of the arm. The plane was packed as usual. We had paid an extra $100 to be able to sit in "economy comfort class". In fairness there was about an extra 4 inches between my knees and the back of the seat in front of me (and I m 5'10'' on a good day). Even that could not make up for the severe ergonomic problems of airplane seating. I would quickly describe those as a lack of upright, even in the upright position. Upright is at least 15-20 degrees from upright and over the course of a 5 hour flight that can create quite a bit of pain in anyone with a back problem. This problem has been studied to some extent as evidenced by bullet point 3 on this web page. The economy comfort class also comes with free alcoholic beverages, and I saw one passenger who was clearly uncomfortable rapidly down 4 drinks. The other ergonomic problem is an ill defined seat. It felt like sitting on 5 or 6 tennis balls all the way.
But back to the focus on viruses. From discussing the problem with friends and family it is almost a universal experience that people get viral illnesses on their flight back from a recreational or work destination.
When I boarded a cruise ship recently I was screened for GI symptoms and asked if I had any recent illnesses as part of the check-in procedure. That did not happen at any point when I got on either of the direct flight to or from Minneapolis. In addition to the screening procedures there was hand sanitizer being actively and passively dispensed throughout the ship and on the ships TV channel the following message played continuously on a 24/7 basis:
Please wash your hands often and use the sanitizer stations provided throughout the ship especially when you are coming from ashore. Always use a fresh cup when using beverage dispensers and refrain from using personal containers directly or on common beverage stations. To stay healthy wash your hands with soap and warm water frequently.
In comparing respiratory infections from air travel to Norovirus infections on cruise ships there are important differences. The Norovirus infections occur in a well defined captive population in very specific time period. If an outbreak occurs it can become widely known, to the public relations detriment of that cruise line. If a respiratory virus is contracted on a flight, everyone leaves the plane after arrival in a few hours and the total number of people infected is unknown. There have been studies that look at the attack rates of people who have been on a flight where there is an index case of influenza and also the effects of using masks prophylactically when there are known index cases onboard. There are no cautions to the passengers about how to prevent the spread of respiratory infections and (to my knowledge) no easy way for them to cancel in the event that they develop an acute upper respiratory in infection. The CDC has some limited guidance on air travel, including some information on influenza transmission cabin air conditioning including the fact that it is partially recirculated and HEPA filtered 15-20 times per hour. The most interesting study in microbial diversity in commercial aircraft that I could find was by Osman, et al (1) who compared conventional culture techniques to available molecular probes in 2008 in samples from 16 domestic and international flights. They conclude that the molecular probe techniques demonstrated a much greater microbial diversity than culture techniques and that microbes varied significantly from domestic to international flights. The molecular probe techniques identified 12 classes and 100 species of bacteria in cabin air, but in sufficiently low concentrations to not present a health hazard. I am aware of studies in the past that have done viral cultures for respiratory viruses on filters in buildings but could not find similar data for commercial aircraft. There have already been simulations about what happens when a person sneezes on an commercial aircraft, and those results are eye-opening. I posted that in a look at the issue of hand washing and respiratory viruses.
Rather than go into excessive detail about the limited research that has been done so far, let me summarize a few facts and my conclusions. Respiratory viruses can be transmitted during commercial air travel. The attack rate for influenza virus has been estimated to be 2 - 4%. There has been at least one study that shows masks can prevent infection. There have been several simulations of how air travel potentially increases the world wide spread of airborne viral infections and some of these infections like corona virus and SARS outbreaks puts a significant burden on the international public health community. Furthermore, the public health burden in terms of both morbidity and mortality is huge. Influenza virus alone kills about 20,000 people annually in the United States or the equivalent of 5 large cruise ships in terms of total lives. By comparison, there if far more press coverage of a Norovirus outbreak on a cruise ship and that virus is much less fatal. Every American contracts about 2 - 3 respiratory viruses per year of varying severity. That probably amounts to about 2-6 weeks of illness per year, associated with a disruption of work and daily activities as well as increased infection risk for those in the sphere of that person's routine. There is also a risk for exacerbation of chronic illnesses like asthma and chronic obstructive pulmonary disease.
All of these considerations lead me to suggest (at the minimum) - the following measures:
1. Intensification of study of airborne diseases especially respiratory viruses: The technology is certainly there and there is no reason that molecular technologies cannot be applied to samples from commercial aircraft and I think that the HEPA filters are a logical place to start. I would really like to see this become a focus of a private research fund, because it seems like the federal government has created numerous monitoring systems but no practical ways to detect high risk scenarios and disrupt disease transmission. It seems like that is likely to occur only after an outbreak of a highly fatal respiratory virus occurs.
2. Passenger education is critical: The airline industry needs to adopt the methodologies that are currently employed in the cruise industry - educating everyone on the plane, screening for passengers at risk and quarantining them if necessary. A critical piece of the education process is that while hand washing is necessary, it is not sufficient to prevent the spread of airborne respiratory viruses. That public needs more awareness of that concept and what else can be done. The method of quarantine is debatable and would probably need some flexibility based on passenger needs and acceptability and the severity of the problem. It could include grounding until the infection clears, use of masks to block airborne infection, or possibly a section of the passenger cabin with more intensive HEPA filtering (altering air flow and humidity can affect the likelihood of virus transmission).
3. Developing a culture to reduce the risk of respiratory virus infection: Everywhere that I look we have practices in place that encourage the transmission of respiratory viruses. Most Americans do not let respiratory viruses stop them from carrying on their business as usual. In the past few days, I have personally walked through clouds of sneezed droplets because I happened to be following a fellow customer or coworker too closely at the wrong time. I can't recall exactly when it happened, but getting rid of sick and vacation time and replacing it with paid time off or PTO days is an incentive for going to work sick. Most of that sickness is respiratory viruses.
The American attitude to the common cold is far too casual. It does not take into account the spectrum of symptom severity and the fact that many of these viruses can cause influenza-like illnesses and very severe syndromes. Even a cold of moderate severity generally curtails a lot of activities and produces significant morbidity. I don't understand how the medical and consumer community has come to this level of acceptance and denial of this collection of more-than-just-a-nuisance pathogens, but I would like to see it stop.
The American attitude toward the bad ergonomics of airline seating is another issue. I think it is unfortunate that most passengers these days have never flown on a 747. I may be overidealizing the flying of my youth, but planes today seem like dismal narrow aluminum tubes by comparison.
George Dawson, MD, DFAPA
References:
1: Osman S, La Duc MT, Dekas A, Newcombe D, Venkateswaran K. Microbial burden and diversity of commercial airline cabin air during short and long durations of travel. ISME J. 2008 May;2(5):482-97. doi: 10.1038/ismej.2008.11. Epub 2008 Feb 7. PubMed PMID: 18256704.
Supplementary 1:
For a graph of the URI I contracted on the Alaska vacation and most likely on the flight home follow this link.
Attribution:
The graphic at the top of the blog is directly from the CDC and one of their pages on Middle East Respiratory Virus Coronavirus. Photographic credit is given to Jennifer L. Harcourt. The picture depicts coronavirus particles in the cytoplasm of an infected cell.
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