Flu, Cold, and now COVID-19: What’s the Difference?

Have you ever gone to the doctor for an upper respiratory infection (URI)? Maybe your symptoms felt different than usual, or you were so miserable you started thinking it might be the flu—or maybe even COVID-19. But after seeing the doctor, you’re told to go home, rest, drink fluids, take some Tylenol, and wait it out. The doctor doesn’t run any tests, and you start wondering, How do they know what I have?

If you clicked on this post, you might be hoping to finally understand how doctors figure out the difference between a cold, the flu, and COVID-19 based on symptoms.

Well, I’m going to burst your bubble a little here: there’s no magic checklist doctors use to instantly know which virus you have. The only way to know for sure whether you have the flu, a cold, or COVID-19 is to get tested.

You might be thinking, “But if I have the flu, I’ll have a high fever or feel so sick I can’t get out of bed, right?” Honestly, not necessarily. People with the common cold can feel just as awful, and some people with the flu have barely any symptoms at all. Everyone’s body reacts a little differently, so it’s really impossible to say for sure without testing.

However, The good news is, it doesn’t matter as much as you might think. All those years you worried about whether you had the flu or a cold—well, you can stop unless you fall into a higher-risk group. We’ll cover why this is the case as we go on.

What Is a Cold, the Flu, or COVID-19?

When we talk about getting a cold, the flu, or COVID-19, we’re really talking about an upper respiratory infection (URI) caused by a virus. Different viruses cause each of these illnesses, but they all affect similar parts of our body—your sinuses, nasal passages, and lungs. Symptoms can range from mild (like sneezing or a sore throat) to severe (like a deep cough or pneumonia). Since the symptoms often overlap, it’s tough to tell which virus you have just by looking at them.

It’s even possible to catch more than one virus at a time and not realize it.

So, Why Doesn’t It Matter?

Now you might be wondering, why doesn’t knowing exactly which virus you have matter more—especially if the symptoms are mild? The simple answer is that it really doesn’t—for most people.

For example, if the flu or COVID-19 only causes mild symptoms like a cough or runny nose, the treatment is basically the same as it would be for a cold with those symptoms. The advice is simple: rest, drink lots of fluids, and take over-the-counter (OTC) medications to manage your symptoms (as recommended by your doctor).

The situation starts to change when your symptoms are more severe or if you’re in a higher-risk group. We’ll get into those details next.

Why Did My Doctor Test for the Flu or COVID-19, or Prescribe Medication?

It really depends on the doctor and the situation. Many doctors won’t recommend testing if the URI is mild because the treatment is usually the same, regardless of the virus. They may feel that testing would just add unnecessary costs without changing the treatment plan. Similarly, if OTC medications will do the trick, there’s no need for a prescription.

In most cases, it’s best to check in with your doctor about OTC treatments and take care of the illness from home. You might not even need to leave the house—many doctors are happy to give advice through online messaging or phone calls.

When Does Testing for a Specific Virus Help?

Testing becomes more important if your symptoms are severe or if you’re in a higher-risk group. For example, antiviral medications like Tamiflu (for the flu) or Paxlovid (for COVID-19) can help if they’re started early: within the first 48 hours for Tamiflu and the first 5 days for Paxlovid. Knowing which virus you have can also guide treatment if things worsen, like if you develop pneumonia or need to go to the hospital.

Testing may also be recommended if you have high-risk factors, even if your symptoms are mild. For instance, older adults (over 65), young children (under 5), or people with chronic conditions (like asthma, heart disease, or diabetes) may benefit from early testing and antiviral treatment. These groups are at higher risk for complications, and antiviral medications can help reduce the chance of the illness getting worse.

When Should You Seek Medical Attention?

As we’ve already discussed, it can be hard to tell the difference between various respiratory viruses based on symptoms alone. It’s also not always clear when you should see a doctor. But a big part of it is learning what’s normal for you when you get a cold or URI. If you know how your body usually reacts, it’s easier to tell when something doesn’t feel right.

That said, there are certain symptoms that should always be taken seriously and might require you to get medical help, like:

• Difficulty breathing, especially when moving around

• High fever (over 101°F) that doesn’t respond to fever-reducing meds like acetaminophen (Tylenol) or ibuprofen

• Fever over 103°F

• Extreme weakness, lethargy, or confusion

If you experience any of these symptoms, you should seek medical attention right away.

I’ve also previously included in a post and on the Educational Resources page of this site a link explaining when to go to the doctor vs. when to go to the hospital. You can find that here: Should you go to the emergency room (ER), urgent care or doctor’s office?.

Summary & Recommendations

I know some of you were probably hoping for a clear way to tell the difference between the flu, a cold, and COVID-19 so you’d know exactly when to visit the doctor or go to the hospital. Unfortunately, as we’ve covered, there’s no easy way to distinguish between these illnesses based on symptoms alone. But hopefully, this post has eased some of the worries around these viruses by explaining how it’s more important to focus on your symptoms and whether you’re in a higher-risk group than it is to worry about which virus you have.

Here are a few things I’d recommend to help you feel more prepared:

1. Know your baseline: Pay attention to how your body usually reacts to a URI so you can tell what’s normal for you—and what isn’t.

2. Home Medical Equipment: These small tools can make a difference in helping you learn your baseline and feel more confident in knowing when to seek medical help.

   1. Pulse Oximeter: https://amzn.to/3YShv8K (I have this one in white, and I like it because it also tells me the PI% as well, which is the strength of the signal, which helps determine accuracy. Above 0.4% is good/reliable)

   2. Thermometer: https://amzn.to/3YShv8K (Here is a link to a tympanic or ear thermometer. Feel free to look around and read reviews. I recommend these types of thermometers because they are rather accurate, easy to use, and quick. These are the thermometers of choice at my work.)

   3. Testing Kit: For those who feel they need the peace of mind of knowing or are concerned about access to rapid testing when they need it. https://amzn.to/4frJfbE

3. Talk to your doctor about OTC treatments: Be sure to ask your doctor which over-the-counter medications are safe for you to take, especially if you have other health conditions or are on prescription meds.

4. Discuss high-risk factors with your doctor: If you have asthma, diabetes, or any other chronic conditions, it’s a good idea to talk to your doctor about how to manage a URI. Should you go to urgent care? When should you go to the ER? Having a plan in place will help you make the right decision if you get sick.

Everyone’s health is different, so it’s important to talk to your doctor about your specific needs. Taking a little time now to discuss your options can help you feel more confident the next time you’re dealing with a respiratory illness.

Here are some reference links to Tamiflu and Paxlovid by the National Institute of Health (NIH) and the 2023-2024 estimated flu burden by the CDC for those who are interested.

Paxlovid: antiviral combination for the treatment of COVID‐19

Oseltamivir (Tamiflu).

Preliminary Estimated Flu Disease Burden 2023–2024 Flu Season | Flu Burden | CDC

Disclaimer: This article may contain affiliate links. The content is based on the personal experiences and opinions of the author(s). Please remember, this is not a substitute for advices from an appropriately licensed medical professional.