Study on the the effect of 9/11 on the flu season

[Adam Shand]

Source: http://www.cbc.ca/story/health/national/2006/09/11/flu- 
delays.html
Grounding of 9/11 flights delayed flu season: study

Last Updated Tue, 12 Sep 2006 12:17:19 EDT

The arrival of flu season was delayed when air traffic stopped after  
the Sept. 11 attacks, a finding that suggests a ban on air travel  
could buy valuable time in the event of a pandemic, a study's authors  
say.

John Brownstein says restricting air travel could delay the arrival  
of a pandemic flu, giving healthcare workers more time to prepare. (CBC)
Researchers in the U.S. studied influenza seasons for nine regions in  
the U.S. between 1996 and 2005.

Study author John Brownstein of Children's Hospital Boston and his  
colleagues looked at how flu spreads between cities and regions and  
calculated the rate of spread each year.

In the years before 9/11, flu deaths in the U.S. tended to peak  
around Feb. 17, the researchers reported in the journal PLoS Medicine.

In the flu season after the attacks, the peak date was delayed by 13  
days, to March 2. In France, where there were no flight restrictions,  
there was no delay in the 2001-02 season.

As air travel in the U.S. picked up again in 2003, flu deaths  
returned to their traditional mid-February peak.

The study also showed seasonal flu cases in the U.S. start to take  
off after American Thanksgiving, when more people fly to be with family.

The researchers tried to look for other reasons for the lag after  
Sept. 11, such as weather and vaccination rates, but couldn't find  
any link.

"Really, it was just the travel, the number of people on flights,  
domestic and international, that influenced the influenza season,"  
said Brownstein.

The findings prompted the team to ask: if restricting air travel  
could delay flu season, could it also delay the arrival of a flu  
pandemic?

Every day might count

Dr. John Oxford doesn't think the delay from restricting air travel  
would make a difference in slowing the spread of a pandemic. (CBC)
The delay would not be enough to make a difference, said Prof. John  
Oxford, an influenza expert at University College London.

"If you stop 99.99 per cent of the flights coming into your country,  
you do two things," said Oxford. "You blow the feet off the economy,  
which is not good, and you don't stop the virus coming in. You delay  
it a little bit."

Others say that in a pandemic, every day will count.

"This could provide significant public health lead time for things  
like stockpiling antiviral therapy, manufacturing a vaccine,"  
Brownstein countered. The researchers acknowledged their findings  
cannot prove travel restrictions would change the course of a flu  
pandemic, but they say it shows air travel plays a major role in the  
annual spread of flu.

Canada's pandemic flu plan doesn't call for restrictions on air  
travel, and it might be needed, said Dr. Ron St. John of the Public  
Health Agency of Canada.

"There will be a dramatic decrease in air travel, without any need  
for restriction," said St. John. "People will just stop travelling,  
and that was evident during SARS."

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