Every year as the summer winds down and school resumes, we all know that flu season is just around the corner. Maybe you’re even feeling a little under the weather right now and wonder if you have the flu or something else.
You’ve probably heard that COVID-19 and the flu can share a lot of the same symptoms. So, how do you tell the difference between COVID-19 symptoms and flu symptoms? The short answer is: It can be tricky. But we’re here to help.
The only way to truly diagnose whether you have the flu or COVID-19 is through testing. But knowing the symptoms of each can help you determine what to do next. Below, we provide an overview of both viruses, similarities and differences between symptoms, when you should get care and more.
COVID-19 vs. the flu: What’s the difference between these two viruses?
The flu and COVID-19 are both highly contagious respiratory illnesses, but they’re caused by different viruses.
The flu is caused by influenza viruses – usually Influenza A or Influenza B viruses – which we experience during our annual flu season (also known as respiratory season).
There are a lot of influenza viruses out there – and flu vaccines have been around since the mid-1940s. Each year, specific flu vaccines are recommended to fight the strains of influenza that research indicates will be the most common that season. So, when you make a flu vaccine appointment, you’ll get the flu shot or nasal flu mist chosen for the most recent flu season.
COVID-19 is caused by a coronavirus called SARS-CoV-2. Our bodies had never experienced this type of virus before the beginning of the 2020 pandemic, which means our bodies hadn’t had a chance to build antibodies to fight it. There are also multiple variants of the coronavirus – some of which are more contagious and have different types of symptoms.
Since December of 2020, scientists and researchers have worked hard to update COVID-19 vaccines to protect against different variants. Beginning in 2023, the Centers for Disease Control and Prevention (CDC) has recommended getting an updated COVID-19 vaccine each fall.
Can the flu turn into COVID-19?
No. The flu cannot turn into COVID-19. And COVID-19 cannot turn into the flu. Again, these two illnesses are caused by different viruses.
Is it possible to have COVID-19 and the flu at the same time?
Yes. It is possible to be infected with the flu, COVID-19 and other respiratory illnesses at the same time. Having both the flu and COVID-19 at once is sometimes referred to as being sick with “flurona”. Being infected with multiple respiratory illnesses can increase your risk of severe complications. To reduce your chance of co-infections, get the recommended flu vaccine and COVID-19 vaccine for this year.
Can I still get sick after I get the flu or COVID-19 vaccine?
If you received your annual flu vaccine, it’s still possible for you to get the flu, but it’s likely that your symptoms will be milder. Similarly, even if you’re up-to-date on your COVID-19 vaccine, it’s possible for you to get breakthrough COVID-19. But if you do get COVID-19, you’ll likely have a mild case that can be treated at home.
How are symptoms of COVID-19 different from the flu?
Flu vs. COVID-19 symptoms: Similarities
Respiratory illnesses often share similar symptoms. That’s because your respiratory system is in charge of helping you breathe, and includes your airways, lungs and blood vessels. So when bacteria or viruses get in, the whole system can be affected and cause similar symptoms.
You may be wondering: Is diarrhea a symptom of COVID-19? Are nausea and throwing up symptoms of COVID-19? The answer to both these questions is yes. You can have gastrointestinal symptoms with both COVID-19 and the flu – but they aren’t the most common symptoms for either illness. The most prominent symptoms that COVID-19 and the flu can have in common include:
- Fever of more than 100 degrees Fahrenheit
- Cough
- Fatigue (extreme tiredness or lack of energy) and weakness
- Headache
- Muscle pain and body aches
- Nausea or vomiting (more common in children than adults)
- Diarrhea (more common in children than adults)
Flu vs. COVID-19 symptoms: Differences
While there are many similarities between COVID-19 and flu symptoms, there are some specific differences, depending on the COVID-19 variant, including:
Symptom onset
The flu comes on suddenly. Usually the first signs of the flu appear anywhere from one to four days after infection. Early flu signs are often fever, muscle aches, fatigue, chills and headache.
The first symptoms of COVID-19 can be more gradual. While COVID-19 symptoms can develop as early as two days after you’re infected, the Centers for Disease Control and Prevention (CDC) says five days after infection is typical. Plus, it’s possible to be infected with COVID-19 but not show any symptoms for up to 14 days – and some people may not have any symptoms at all.
You may be wondering: What are the first signs of COVID-19? Unfortunately, it’s hard to say. COVID-19 affects people in different ways and depends a lot on what variant of COVID-19 they have.
Cough type and severity
The flu usually causes a mild, dry cough. COVID-19 variants affect the lungs in different ways, so you may or may not have a cough.
The presence of a fever
One question that we’ve been hearing a lot is, “Can you have COVID-19 without a fever?” The answer is yes. While you’ll almost always have a fever over 100◦F with the flu, it’s possible to have COVID-19 with a low-grade fever (less than 100◦F) or no fever at all.
Maybe you’re wondering: How long does COVID-19 fever last? Like most things with COVID-19, it varies. Some people can have a low-grade fever for weeks after their initial infection. If your temperature continues to be low, it’s generally nothing to worry about. But if your temperature stays above 100.4◦F for more than 2-3 days and you can’t control it with medication, seek medical advice. You can start by calling the HealthPartners CareLine℠ at 800-551-0859 or the Park Nicollet Nurse Line at 952-993-4665.
COVID-19 is sometimes more like a cold
The severity of your COVID-19 symptoms depend a lot on the variant you have. Right now, Omicron subvariants are most common and come with mild symptoms such as a stuffy or runny nose, a sore throat and a headache – the kind of symptoms that are more common with a cold versus the flu. The Delta variant, which was more common at the height of the pandemic, usually came with a high fever and a painful cough.
But even if COVID-19 feels like a cold, it’s still very contagious. And, it’s possible that if it spreads to others, they could get much sicker – especially if they’re older, have weakened immune systems or are unvaccinated. So, it’s a good idea to test for COVID-19, when you have cold or flu-like symptoms even if you don’t have a fever.
Unique symptoms
There are some COVID-19 symptoms that don’t typically overlap with the flu or the common cold, including:
- New and sudden loss of taste or smell
- Shortness of breath or difficulty breathing
- Dry mouth
Having these symptoms doesn’t mean that you have COVID-19, but it could be more likely. If your symptoms are severe, seek immediate medical care. Call 911 if you have shortness of breath, persistent pain or pressure in your chest, or have a hard time staying awake.
Is there a difference between COVID-19 and flu symptoms in adults and children? Men and women?
We’re often asked if flu symptoms in children are different than in adults. And this has become one of the most common questions about COVID-19.
Generally speaking, COVID-19 symptoms and influenza symptoms are the same for males and females – young or old. However, those with severe underlying medical conditions seem to be at higher risk for more serious complications. Also, there are a couple things to note when it comes to COVID-19 symptoms in children.
Gastrointestinal issues are more common in kids
For both COVID-19 and the flu, when vomiting, nausea or diarrhea happens, it’s usually more common in children than adults. This also means that the risk of dehydration can increase. So, parents should watch for signs of dehydration such as dry mouth, no tears when crying, or no urine for 8 or more hours.
COVID-19 has been linked to another condition in kids
COVID-19 usually causes mild symptoms in children. However, some children have developed what’s called multisystem inflammatory syndrome (MIS-C). MIS-C is a condition where different parts of the body (not just the respiratory system) become inflamed. So, in addition to common COVID-19 and flu symptoms like fever, fatigue, vomiting or diarrhea, other symptoms can include abdominal pain, neck pain, rash and bloodshot eyes.
Right now, information on this condition is limited, but the CDC is working closely with local health departments to learn more. If you want to learn more about the condition, we encourage you to visit the CDC’s MIS-C information page.
Comparing COVID-19 and flu symptoms
We’ve gone through the symptom similarities and differences between the flu and COVID-19. But here’s how they compare side-by-side.
| Signs and symptoms | Influenza | COVID-19 |
|---|---|---|
| Onset of symptoms | Sudden | Gradual |
| Fever above 100°F | Almost always, lasts 3-4 days | Sometimes, lasts 2-7 days |
| Chills | Common | Common |
| Headache | Common | Common |
| Cough | Dry, sometimes severe | Sometimes, can be severe |
| Sore throat | Sometimes | Common and often more prominent |
| Dry mouth | Rare | Sometimes |
| Runny or stuffy nose | Sometimes | Common |
| Shortness of breath or difficulty breathing | Sometimes | Common and often prominent |
| Muscle pain or body aches | Usual, often severe | Common |
| Repeated shaking with chills | Rare | Sometimes |
| Fatigue (extreme tiredness or lack of energy) | Early and prominent | Common |
| Diarrhea | Sometimes (more common in children) | Sometimes (more common in children) |
| Vomiting or nausea | Sometimes (more common in children) | Sometimes (more common in children) |
| Sudden loss of taste or smell | Never | Sometimes |
What to do if you have COVID-like or flu-like symptoms
COVID-19 and influenza are highly contagious viruses. If you’re experiencing any symptoms or you’re not sure if your symptoms are a match, don’t worry. Here are a few steps you can take:
Stay home and test for COVID-19
In general, it’s recommended that you stay home if you have a fever and for at least 24 hours after your fever goes away (without the help of medications like acetaminophen or ibuprofen). If you don’t have a fever, but you have other COVID-19 or flu symptoms, take an at-home COVID-19 test before you’re around other people.
Multiple antigen tests may be necessary since it’s possible to get a false negative result. So, the Food and Drug Administration recommends testing at least twice over three days with at least 48 hours between tests. If you have two negative results from antigen tests, you’re considered negative for COVID-19.
Another option is to schedule a PCR test at your local clinic. PCR tests provide more reliable results, so you’ll only need one test to find out if you’re negative or positive for COVID-19.
If you’re negative for COVID-19, home treatments for the flu might be all you need. And if you’re positive for COVID-19, you should be able to treat COVID-19 at home – but be on the lookout for more serious symptoms.
Call one of our care lines for advice
Our care lines allow you to talk directly with a nurse 24/7, 365 days a year completely free of charge. They can help you decide if it’s time to see a doctor, as well as provide helpful home remedy advice. To get in touch, call the HealthPartners CareLine℠ at 800-551-0859 or the Park Nicollet Nurse Line at 952-993-4665.
Get treatment and care virtually
Whether you’re stuck at home with a fever or you aren’t ready to leave your house just yet, there are easy ways to get quality care that fits your preferences. Here’s how:
- Make a video visit appointment to meet with your preferred primary care doctor or a clinician.
- Start a Virtuwell visit without an appointment. Just answer a few questions, and you’ll get your diagnosis and treatment plan from a board-certified nurse practitioner.
Try to relax and take care of yourself
If you’re not feeling well or you’ve been officially diagnosed with an illness, try to get lots of rest and stay hydrated. Also, talk with your doctor about which over-the-counter medications they recommend to help reduce your fever, aches and pains.
Go to the emergency room if serious symptoms arise
Both the flu and COVID-19 can have serious complications. Go to your nearest emergency room if you or your child is experiencing any of the following symptoms:
- Difficulty breathing
- Flu-like symptoms that improved but then returned worse
- Chest pain or pressure
- Sudden dizziness or confusion
- Severe or persistent vomiting
And, more specifically for children, go to the emergency room if your child:
- Is less than 3 months old and has a fever above 100.4° Fahrenheit
- Is between 3 months old and 3 years old, has a fever above 100.4° Fahrenheit, and is showing signs of dehydration (e.g., dry eyes or mouth, hasn’t urinated in several hours)
- Has a fever with a rash
- Has skin or lips that have turned gray or blue
- Is extremely irritable
- Is not eating or drinking
- Is not waking up or interacting with you
What can you do to stay as healthy as possible? Get a COVID-19 vaccine and flu shot this year
The best way to protect yourself and others from influenza and COVID-19 is by getting updated vaccines for both viruses when they become available each year.
When you get a flu shot, you’re up to 60% less likely to get the flu, according to the CDC. And studies also show that even if you do get sick, your flu symptoms will be less severe and you’re less likely to need hospital care to recover.
When it comes to COVID-19, data suggests that vaccines are effective in preventing illness from COVID-19, with the greatest protection coming against severe illness, hospitalization and death.
You can make an appointment for this year’s flu and COVID-19 vaccines once they’re available, usually in September.