Public health experts blame a big parade for giving a boost to the international 1918 flu epidemic that killed more than 12,000 Philadelphians.  The event to sell war bonds brought together thousands of vulnerable citizens at a time when sick sailors in from Boston (yes, Boston) were spreading a particularly deadly form of the virus.

Now, the city is planning a giant parade to celebrate the Eagles' Super Bowl win at the height of what has been an unusually tough flu season.  Is that a good idea?

Infectious-disease experts said Thursday's big event could indeed help spread the flu, but this isn't 1918.

An aircraft hull was part of the Liberty Loan parade in Philadelphia in 1918 blamed for spreading a flu virus that killed more than 12,000 in the city.
An aircraft hull was part of the Liberty Loan parade in Philadelphia in 1918 blamed for spreading a flu virus that killed more than 12,000 in the city.

For one thing, this year's flu strains are nowhere near as deadly as the virus that wreaked havoc during that infamous season a century ago.  "That virus was a killer, literally," said Thomas Fekete, an infectious-disease specialist and chair of internal medicine at Temple University Hospital. And it was swift too, dispatching people within a day or two of displaying symptoms.

Neil Fishman
Courtesy of Penn Medicine
Neil Fishman

For another, the 1918 parade was held in the fall, when most people had not yet been exposed to the virus.  The Eagles parade is coming after people have already been around flu for weeks.  Plenty of us are still going to get it — no matter what — but many people at the parade will already be immune.  Neil Fishman, chief medical officer at the Hospital of the University of Pennsylvania, added that the city's population was much lower 100 years ago.  Now, the region is far more congested, so a parade is just one of many times that people are packed together.

And, of course, there was no flu vaccine in 1918.  While the current shot has not been very effective against this year's worst strain of flu, H3N2, it is better for influenza B, which is also making a strong showing at the moment.

"Transmission is rampant in the community now, and you have to assume that many people are infected or have been exposed to influenza already," Fishman said.  "I don't think the parade is going to worsen the flu season we're having."

People risk exposure to flu anywhere they go now, said Fekete and Henry Fraimow, an infectious-disease doctor at Cooper University Hospital.

Thomas Fekete
Courtesy of Temple University Hospital
Thomas Fekete

Being cooped up in a crowded house or bar on Sunday with a bunch of screaming, hugging, kissing fans was also a pretty good way to get the flu.  One reason that respiratory viruses spread so well this time of year is that people stay inside together where the air recirculates, Fekete said. Normally, being outside would be better, but fans could be packed tight while watching the parade and while riding on public transportation.

Flu spreads through respiratory secretions transmitted by coughing, sneezing and breathing. Touching an infected surface and then your nose, mouth, or eyes will also do the trick.  Flu victims can spread germs to people up to six feet away for a day before they have symptoms and for up to a week afterward.  The incubation period averages two days, so you could pay for your fandom on the weekend.

Fraimow said there are likely weeks left in this flu season, and it's hard to hide from it. "The risk of ongoing exposure to flu is going to be there anyway, whether you attend the parade or not," he said.

Henry Fraimow
Courtesy of Cooper University Health Care
Henry Fraimow

Fekete pointed out that there are lots of big events this time of year — concerts, basketball games, inaugurations — that don't markedly change the course of flu. "We don't normally lose a lot of sleep over it," he said.

He couldn't predict whether a huge parade would add to the total numbers of people who get sick this year. It could just make some susceptible people sick a few weeks earlier.

Doctors said there are a lot of other respiratory viruses out there now, including two that cause colds as well as respiratory syncytial virus (RSV), which, like flu, can cause serious illness in young children and the elderly.

One thing you can do to try to protect yourself in a close crowd is to take along some hand sanitizer and use it. Fraimow says wearing a surgical mask can help, but Fekete doesn't think that would be much fun. "I don't think it makes any sense to go to a rally and scream with a mask on," he said.

The doctors agree on one thing:  If you've got the flu, stay home.

Because young children and the elderly are most likely to have serious problems when they get the flu, Fishman said, it would be a good idea for them to stay home.  They're likely to be miserable in the cold anyway.