Des Moines University Clinic Health Topics | How does the flu vaccine actually work?

Everything you need to know about the flu

We’re coming up on the start of flu season, everybody is gearing up for colder weather and coronavirus is dominating the news cycle. So, it seems like a legitimate time to talk about influenza, right? Maybe? Well, here’s the thing: It’s always a good time to talk about the flu.

Realize this: Influenza is here forever, there are a bunch of misconceptions around it that we need to address.


The history of influenza

Influenza has been a major problem for as long as people have been around. Hippocrates (yeah, the Oath Guy) gave us one of the first records of the illness around 410 BC, describing a highly contagious disease spreading across northern Greece. Obviously we can’t know for sure if he was talking about the influenza virus as we know it today, but the characteristics he wrote down are suspiciously reminiscent of the modern day flu. The actual word influenza started in Florence, Italy in 1357 during an epidemic where the disease was referred to as “influenza di freddo” (which means “cold influence” if your Italian isn’t up to snuff). The term was thought to have arisen from the disease’s association with cold weather.


A tale of two flus

There are actually two “influenzas” out there. The first influenza is the viral influenza we are all familiar with. There’s also a bacteria called haemophilus influenzae. It was sort of mistakenly named that by a doctor named Richard Pfeiffer; I say “mistakenly” because it makes things a little confusing. Dr. Pfeiffer isolated a bacteria from patients who were particularly sick with a disease that at the time was termed influenza and then decided to name the bug haemophilus influenzae. I shouldn’t be too hard on him because at the time, nobody knew what a virus was and certainly couldn’t isolate one.

The problem with naming the bacteria after influenza is that many of the patients didn’t actually have a bacterial infection, they actually had a viral infection and now both names stuck. This has managed to confuse many a patient as well as many a medical student because the two things are named the same, but they’re very, very different.

Haemophilus Influenzae— the bacteria (we call it H.Flu for short)—can be killed by antibiotics.  Influenza—the virus—absolutely cannot. Almost universally when you get the flu, you’ve contracted the virus; the only way to know if you got H.Flu is through a bacterial culture. If you get tested for the flu in a doctor’s office and it comes back positive for influenza A or influenza B, you have the virus. It’s also important to note that you need to physically be tested for the flu to say you have the flu. There are countless other respiratory viruses out there that can make you sick, most of which are not influenza.


How does the flu spread?

There are a few other misconceptions to clear up, starting with this: There’s no such thing as the stomach flu. Influenza is strictly a respiratory illness. What many people call the stomach flu health professionals call gastroenteritis, which is fancy way of saying that your stomach and your intestines are inflamed and irritated. Now, this is usually caused by a virus but it’s never, ever caused by the influenza virus—hence the reason there’s no such thing as the stomach flu.

This might seem nitpicky, but there are some real practical consequences. A treatment for influenza called oseltamivir (aka Tamiflu) won’t do anything for gastroenteritis, and might actually make symptoms worse, since Tamiflu is kind of hard on a person’s stomach.

It’s also important to note the way that influenza is spread compared to the way viral gastroenteritis is spread. Viral gastroenteritis is usually spread through fecal/oral transmission. There are some exceptions, but basically if you get a viral gastroenteritis…well…I don’t know how to tell you this but there was a very, very, very small amount of infected poo that got in your mouth. This doesn’t mean that you’re an unclean person; it most likely means that somebody with gastroenteritis didn’t wash their hands properly and then shook your hand or made you something to eat. That’s why, obviously, employees are supposed to wash their hands before returning to work.

Viral influenza is much, much more contagious than that. It is so contagious that people can put virus out into the world simply by talking or breathing quietly. Influenza is airborne, meaning that the virus can live in small micro-droplets of water that float around in the air waiting for us to breath them in. By the way, initially, coronaviruses were thought to not be as viable in smaller droplets, meaning that they were less airborne. Unfortunately, we’ve discovered that this isn’t the case and coronaviruses are quite comfortable in small droplets. This, very sadly, means that SARS-CoV-2 (THE coronavirus) can be transmitted more easily than many people thought back in March and April. SARS-CoV-2 doesn’t spread through the air quite as easily as the flu, but it’s much closer than we’d like it to be.

Let’s propose a scenario: You’re having a conversation with somebody five feet away. They aren’t coughing, you aren’t touching, and neither of you show any other symptoms of illness.

  1. If that person had any version of viral gastroenteritis, you almost certainly wouldn’t get it.
  2. If that person had a coronavirus (including SARS-CoV-2), you might very well get it – we’re still learning more about the virus everyday, but why take a chance?  (so wear a mask!)
  3. If that person had influenza and you didn’t get a flu shot, we know definitively you have a real chance of getting it.

Are we seeing another flu epidemic?

The most famous influenza pandemic was the so-called Spanish Flu of 1918. It infected an estimated 500,000,000 people (a third of the world’s population at the time) and killed at least 50 million. There were several factors that went into this (most notably a particularly hellish world war that spread influenza among soldiers), but presently we can do quite a bit better than a 1-in-10 death rate during flu season.

First and foremost, we have the flu shot which—even if you end up getting the flu—lessens the severity of the symptoms. Yes, yes it does. Please don’t argue this point. 

We also have something called oseltamivir (aka that Tamiflu I mentioned earlier), which manages to stop the spread of the flu virus when it gets into your lungs. The thing with Tamiflu, though, is you have to take it within 48 hours of symptom onset, otherwise it’s not really effective; if you wait too long, the virus will have already multiplied and spread throughout your lungs. Tamiflu doesn’t kill virus (after all, viruses aren’t technically alive), it only seeks to stop the spread. After about 48 hours, the virus will spread as much as it needs to get you sick.

Face masks do prevent the spread of influenza, which is why if you’re feel ill, please wear one when you visit the doctor’s office.

And, as always, thoroughly wash your hands.


What if I don’t get a flu shot?

The flu vaccine isn’t perfect, but it absolutely prevents hospitalizations. Go get one right now. Especially amid the coronavirus outbreak, we need to preserve as many hospital resources and personnel as possible to help those affected by Covid-19 or whatever the next pandemic coming happens to be. It’s very frustrating to watch health care resources and dollars get used up by something that can be prevented (not always, true enough, but it can be). Annually, more Americans die from influenza than they do it motor vehicle accidents, so the numbers really are significant. 

As long as the flu shot is available in doctors’ offices or pharmacies, it can still be a benefit to you. We see influenza cases into April and I’ve even seen one in May; like I said, influenza is here forever. If you’re on the fence about getting your flu shot and I haven’t gotten mine yet, come on in. We’ll get our flu shots together (because there’s no way I’m going into flu season without one – believe that!).


Need to get your flu shot? The Des Moines University Family Medicine Clinic can help. Visit the DMU Clinic website or call 515-271-1710 to schedule your appointment today.

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Jonathan Crosbie, D.O.

Dr. Crosbie is an assistant professor in the Departments of Osteopathic Medicine and Family and Internal Medicine at Des Moines University. In addition to his academic responsibilities and providing excellent patient care in the Family Medicine Clinic he is an avid activist for preventative medicine and living a healthy lifestyle. In his spare time he enjoys motorcycling, woodworking, movies and sports, and spending time with his family.

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