Every fall you see the news reports, school notices, and health alerts about flu season. Why is it this time of the year? Scientific research indicates that a number of variables interacting together influence flu season. Factors include global and local weather that impacts virus survival; human interactions, such as crowding or air travel; as well as human immune systems and the adaptation of flu viruses to form new strains.1
Flu Germs and Air Travel
The number of factors contributing to the spread of the flu may help explain why the flu season coincides with a spike in air travel during winter months compared to a lack of the same trend during the summer vacation travel peak.
Airline travel, particularly during cold, dry winter months, can help spread flu virus across the country, though it is not necessary for the spread. Research led by the Harvard-MIT Division of Health Sciences and Technology found that domestic airline travel volume in November, especially around the Thanksgiving holiday, was an accurate indicator of how rapidly a flu virus would spread.2 They also found that international travel in September was predictive of the seasonal peak. Their research was further supported by the delayed 2001 to 2002 flu season corresponding with the decline in international air travel after the September 11 terrorist attacks. The trend returned to baseline when travel activity resumed.2 However, a recent publication by Bajardi, et al., suggests H1N1 air travel restrictions were of no help in limiting spread—that it is not necessary for flu virus to catch a ride.3
Though cold and flu virus can spread regardless, airplanes allow people and germs to move across the country at a rapid pace. The combination of drier air and people spending more time indoors enables the germs to survive during these times of the year and to migrate.
What You Can Do to Avoid Cold and Flu Germs En Route
There’s no getting around it; germs will spread, and the cold and flu season will come and go. Now that you know how air travel can contribute to its spread, you can take appropriate measures before and during travel to protect your health, as well as that of others.
The US Centers for Disease Control and Prevention recommend that you4:
- Only travel when you feel well.
- Cover your cough or sneeze with a tissue, not your hands; cough/sneeze into your elbow.
- Avoid touching your eyes, nose, and mouth.
- Avoid close contact with sick people.
- Wash your hands frequently with soap and water when available; use hand sanitizer if soap and water are not available.
- Lofgren, E., Fefferman, N.H., Naumov, E.N., et al. Influenza seasonality: underlying causes and modeling theories. Journal of Virology. 200781:5429–5436.
- Brownstein, J.S., Wolfe, C.J., Mandl, K.D. Empirical evidence for the effect of airline travel on inter-regional influenza spread in the United States. PLoS Medicine. 2006 Sep;3(10):1826-1835: e401. Available at: http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=Retrieve&list_uids=16968115.
- Bajardi, P., Poletto, C., Ramasco, J.J., et al. Human mobility networks, travel restrictions, and the global spread of 2009 H1N1 pandemic. PLoS One. 2011 Jan 31;6(1):1-8:e16591.
- Centers for Disease Control and Prevention (CDC). Flu-Free, Healthy Travel This Winter. Available at: http://www.cdc.gov/Features/WinterTravel/. Accessed March 11.