Coming down with the flu is miserable enough. But, believe it or not, it could get worse.
Imagine having two forms of the illness — at the same time.
Even if you’re already suffering from the flu, you can also catch other viruses and bacterial infections at the same time.
You can also get the flu more than once within a single season.
And you can even be sickened with multiple types of the flu at once.
Thankfully, all of those scenarios are quite uncommon, experts say.
“It’s very rare,” said Dr. Burke A. Cunha, chief of the Infection Diseases Division at NYU Winthrop Hospital and professor at the State University of New York School of Medicine Stony Brook. “None of these things happen very often.”
Here’s an overview of what we know about each of those possibilities:
Multiple types of flu at once
Experts said this is probably the most unusual of the scenarios.
“We rarely see it,” said Dr. Pedro Piedra, professor of molecular virology and microbiology and of pediatrics at Baylor College of Medicine in Houston. “They’re not generally common.”
Because it’s rare, there’s just not enough evidence to say whether having multiple types of the flu simultaneously leads to significantly worse symptoms or outcomes for patients, experts said.
“The data out there on these co-infections are really limited right now,” said Dr. Steven Drews, associate professor in the Department of Laboratory Medicine and Pathology at the University of Alberta in Canada.
“People just don’t really know,” if having multiple flu types at once causes worse symptoms, said Amanda Jamieson, assistant professor of molecular microbiology and immunology at Brown University. “It doesn’t happen that commonly. You just have to have pretty bad luck.”
Part of the reason such so-called co-infections are so unusual is that typically one type of flu tends to dominate each season.
This season, for example, a type of flu called H3N2 is far and away the most common strain of the flu out there. So the odds of catching one of the other flu types is already fairly low, and the odds of catching multiple flu types at the same time becomes even less likely.
Another factor that limits the odds of this occurring: Flu shots.
The vaccines generally help prevent people from catching the flu. Even in seasons where they aren’t all that effective at preventing the spread of one type of flu, the shots may be more effective against another flu type.
This year, vaccinations have been less effective than hoped in fending off H3N2, but they’ve performed better in preventing some of the other flu types circulating.
Getting the flu multiple times in a season
Another scenario is for a person to get the flu more than once in the same season.
You cannot get the same exact type of flu multiple times in a season, because, after the initial infection in a season, your body builds immunity to that type, preventing it from being infected again that season.
But that immunity doesn’t protect you from the other flu types circulating.
So, for example, earlier this season you might have contracted the dominant strain going around, H3N2, but there are still three other types out there that, while less prevalent, could infect you before this season ends.
Dealing with the flu once, only to get it a few weeks or months later, is obviously not fun, which is why doctors urge people to get vaccinated each season, even if they’ve already come down with the flu previously during that season.
On a conference call last month with officials from the US Centers for Disease Control and Prevention, a reporter asked a question about people getting multiple types of the flu at once or during the same season.
It “definitely happens,” said Dr. Anne Schuchat, the CDC’s acting director.
“It’s one of the reasons we say, ‘Even if you have already had the flu this season, it makes sense to get vaccinated because it could protect you against the other strain[s],’ ” Schuchat said. “In a season that’s so intense like this, we may hear of more of those cases.”
But experts said it’s also true that some people mistakenly assume they’ve gotten the flu once or multiple times in a season, when in fact one or all of their bouts with flu-like symptoms were caused by an affliction other than the flu.
“A lot of people say they have the flu when they really don’t. They just have a bad cold that’s caused by another virus,” said Jamieson.
Infected with the flu and another virus
People can also contract both the flu and an entirely different virus at the same time.
Experts said the data on these cases are also limited and it’s not entirely clear whether people are affected differently by having both at once.
“You would think that if you were infected with two viruses you’d have worse symptoms, but it’s been hard-pressed to determine if that’s really the case,” said Dr. Todd W. Rice, associate professor of medicine at Vanderbilt University Medical Center.
Sick with the flu and a bacterial infection
Experts agreed the most problematic scenario is when a person has both the flu and a bacterial infection at once.
“That’s the one we would worry most about,” Piedra said. “Those tend to be the more severe.”
One example is when a person who catches the flu also comes down with bacterial pneumonia.
“The data we have in this area shows that those patients are definitely sicker,” when they have both the flu and a bacterial infection, said Rice.Matt Rocheleau can be reached at email@example.com. Follow him on Twitter @mrochele