Air travel and flu: Post-9/11 restrictions delayed start of season
The onset of the flu season in the USA has been shown to be influenced by air travel. After flights were restricted following the 9/11 terrorist attacks in 2001, the flu season started about two weeks later than usual.
In both the northern and southern hemispheres, influenza epidemics occur annually during the winter flu season. Given the concerns about global epidemics of serious strains of flu, such as occurred in 1918, as well as the more recent, localized outbreaks of 'bird flu', it is important to know more about how flu spreads round the world. Might airline travel play a role in the spread of the infection across large distances? If so, reducing or restricting air travel might be useful in the early stages of a serious global epidemic. Research at the Children's Hospital Boston, now published in PLoS Medicine, has investigated the effects of air travel on the annual spread of flu in the US.
The researchers analyzed government records on deaths from flu and pneumonia in cities from nine regions of the US between 1996 and 2005. For each year, they determined the time it took for the epidemic to spread across the country and the date of the national peak in flu deaths. They used government estimates of passenger air travel to explore any connection with the timing of the annual flu epidemics.
They found the usual time taken for a flu epidemic to reach peak levels across the US was about two weeks, and that the national peak date was within two days of the average date – February 17. Flu spread more slowly in years when the number of domestic air travelers was lower. However, the most striking finding was that the peak date of the US flu season following September 11, 2001 was delayed, by 13 days, to March 2. Following the terrorist attack, there were restrictions on air travel and many people themselves chose to use other forms of transport.
The peak date then returned to February 17 over the subsequent two flu seasons, when international airline travel went back to its previous level. In contrast, the researchers found no delay in the 2001–2002 flu season in France, where there were no flight restrictions. Although other factors may possibly have been involved, the findings suggest that air travel affects both the peak date and the rate of spread of flu. This does not prove that travel restriction would be effective in altering the course of a flu pandemic, but it does provide evidence that air travel plays a significant role in the annual spread of flu in the United States. The findings will help plan for the next flu pandemic.
Citation: Brownstein JS, Wolfe CJ, Mandl KD (2006) Empirical evidence for the effect of airline travel on inter-regional influenza spread in the United States. PLoS Med 3(10): e401.
PLEASE ADD THE LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://dx.doi.org/10.1371/journal.pmed.0030401
PRESS-ONLY PREVIEW OF THE ARTICLE: http://www.plos.org/press/plme-03-10-brownstein.pdf
Related image for press use: http://www.plos.org/press/plme-03-10-brownstein.jpg
- Caption: Seasonal variability in the regional timing of influenza mortality in the United States (1996-2005)
Harvard Medical School
Harvard-MIT Division of Health Sciences and Technology
1 Autumn St
Boston, MA 02215 United States of America
About PLoS Medicine
PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org
About the Public Library of Science
The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org
All works published in PLoS Medicine are open access. Everything is immediately available without cost to anyone, anywhere--to read, download, redistribute, include in databases, and otherwise use--subject only to the condition that the original authorship is properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.
Last reviewed: By John M. Grohol, Psy.D. on 30 Apr 2016
Published on PsychCentral.com. All rights reserved.