Covid-19 and Flu Season: Answering All Your Questions

Fact checked by Olga Sadouskaya, MD
Clinical Pharmacologist, Chief Medical Officer

The COVID-19 pandemic is far from over. At the same time, the Northern hemisphere marks the beginning of the flu season.

But how do you tell these two diseases apart? Which is more dangerous? Can you protect yourself against COVID-19 and the flu at the same time? There are a lot of questions about the novel coronavirus, and we’ll try to answer some of them.

What’s the difference between flu and coronavirus?

The seasonal flu and the new coronavirus have similar symptoms, but there are some significant differences between them. Let’s look at these in more detail.


Both COVID-19 and influenza (the flu) are respiratory infections that share some common symptoms. However, they’re caused by entirely different viruses.

COVID-19 is caused by a new kind of coronavirus called SARS-CoV-2. Coronaviruses are a family of viruses that have crown-like spikes (hence the name). They mostly affect animals, but seven coronaviruses have been known to cause illness in humans.

Fortunately, four of these seven viruses only cause mild symptoms so they’re not considered dangerous. The remaining three are:

  • Severe acute respiratory syndrome coronavirus (SARS-CoV), which caused the SARS outbreak in 2002-2003
  • Middle East respiratory syndrome (MERS-CoV), which was first identified in 2012 and still causes local outbreaks
  • SARS-CoV-2, the virus that caused the current pandemic

The flu is caused by four types of influenza viruses: A, B, C, and D. Most cases of seasonal flu are caused by types A and B, whereas influenza C causes mild symptoms and influenza D only affects animals. Influenza viruses are not coronaviruses.

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Influenza and COVID-19 share many symptoms so it’s not always easy to tell them apart without a test. However, people who have COVID-19 are more likely to lose their sense of smell and/or taste. Also, people with COVID-19 tend to show symptoms about 5 days after being infected whereas flu patients typically have their first symptoms sooner, sometimes just one day after catching the virus.


People who have COVID-19 have a higher risk of complications than people with the flu. In addition to this, coronavirus infections are more likely to cause blood clots.

Another reason why COVID-19 is more dangerous is the risk of long-term complications known as “long COVID”. These can occur even if the infection didn’t cause severe symptoms.

Some examples of long COVID are brain fog, fatigue, feeling worse after physical activity, headaches, depression, anxiety, and joint pain. These health problems can last for weeks or even months.

An old man wearing a face mask during covid and flu season

People who are at risk

Both diseases are particularly dangerous for older people and people with chronic health conditions, as well as during pregnancy. But there’s a difference in the way these infections affect children. The flu can make babies and young children very ill. On the other hand, severe COVID-19 cases among children are rare.

Treatment options

The flu has been around for a very long time, so scientists know a lot about influenza viruses. This is why they could develop several antiviral drugs that are specifically prescribed to patients with a high risk of influenza complications. There are four FDA-approved antiviral medications for the flu:

  • oseltamivir phosphate (known as Tamiflu®),
  • zanamivir (trade name Relenza®)
  • peramivir (trade name Rapivab®)
  • baloxavir marboxil (trade name Xofluza®)

On the other hand, SARS-CoV-2 has only been around since 2019, so researchers are still learning about it and working on effective drugs. As of now, only one antiviral drug called remdesivir has been approved to treat COVID-19.

Are there any similarities between COVID and flu?

Both infections spread in a similar way and can affect vital organs like the lungs and the heart. The main symptoms are also quite similar:

  • Fever
  • Fatigue
  • Cough
  • Shortness of breath
  • Sore throat
  • Runny or stuffy nose
  • Body aches
  • Headaches
  • Vomiting or diarrhea

It can be hard to tell if someone has COVID-19 or the flu just by looking at their symptoms. This is why people have to be tested.

The complications of influenza and COVID-19 are similar, too. They include:

  • Bacterial or fungal pneumonia
  • Respiratory failure
  • Heart attack
  • Stroke
  • Kidney failure
  • Inflammation of the heart or the brain
  • Worsening of preexisting medical conditions
  • Secondary infections (this is when someone develops a bacterial or fungal infection while being sick with the flu or COVID-19)

What coronavirus and flu precautions should you take?

Influenza and COVID-19 spread in similar ways, mostly via water droplets that spread in the air when infected people talk, sneeze, or cough. This is why the precautions for coronavirus and the flu are very similar, too:

  • Wash your hands regularly
  • Avoid touching your face (if a sick person sneezes on a surface, you touch it and then rub your eyes, you could get infected)
  • Avoid crowds, especially indoors
  • Stay home if you experience any symptoms that could be COVID-19 or the flu
  • Avoid people who are sick
  • Clean surfaces that get touched a lot, like doorknobs
  • Get vaccinated
  • Cover your face when coughing or sneezing
  • Wear a mask indoors and in crowded areas — this will reduce the spread of both coronavirus and influenza 

When does the flu season end?

You can get the flu at any time of the year, even when flu season ends.

However, influenza cases spike when the air outside becomes colder and drier, and then drop again when temperatures and humidity rise. In the Northern hemisphere, the flu season usually falls between October and April. In the Southern hemisphere, it typically falls between April and October.

But why is flu season usually in winter? Cold temperatures make us spend more time indoors so you’re more likely to breathe “someone else’s” air and inhale any viruses that could be there. 

Also, viruses tend to survive better in dry air — and winter air is typically dry.

The exact duration of the flu season depends on the weather and the exact strains of the flu virus that circulate in any given year. However, the flu season typically ends somewhere around mid-spring.

Can you have both a flu vaccine and a COVID vaccine?

While the flu and COVID-19 have similar symptoms, they’re two distinct diseases. This is why each one requires a different vaccine.

Fortunately, this doesn’t mean that you need to schedule two appointments with your doctor. Data shows that it’s safe to get both vaccines on the same day. The vaccines won’t interact in harmful ways.

A young man in a face mask getting a covid vaccine

The best time to get a flu vaccine is at least two weeks before the flu season begins because it takes some time for your body to build immunity against influenza. However, you can get vaccinated anytime during the flu season — just remember that the vaccine doesn’t provide you with instant protection. And if you need to get your COVID shot at the same time, go for it! 

Does wearing a mask protect you from flu and coronavirus?

Influenza viruses and coronaviruses spread when a sick person releases water droplets by speaking, sneezing, or coughing. Masks trap these droplets and prevent them from spreading so an infected person doesn’t infect others so easily. At the same time, masks also protect the wearer from inhaling water droplets that came from other people.

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The more snug your mask is, the more protection it offers. Of course, no face covering can filter out every single virus particle, but real-world data shows that masks do help reduce the transmission of respiratory viruses. So it’s a good idea to wear a mask indoors or in crowded places even if your local legislation doesn’t require it.

When to see a doctor if you have flu symptoms?

Most people who develop flu-like symptoms will get well within a week or two. If you’re not in a high-risk group, you can stay home, ease your flu symptoms with over-the-counter remedies, and do your best to avoid infecting other people.

However, some people should call their doctor early in their illness because they’re at a higher risk of developing complications. You belong to a higher-risk group if you:

  • Are over 65 years old
  • Are pregnant or less than two weeks postpartum
  • Have heart disease
  • Suffer from asthma
  • Have kidney or liver disorders
  • Have a health condition that affects your immunity, like AIDS or cancer
  • Take medications that weaken your immune system

Young children also have a higher risk of flu complications. 

If a young family member has flu-like symptoms, call their pediatrician as soon as possible.

You should also seek immediate medical attention if you develop severe symptoms that include:

  • Chest pain
  • Trouble breathing
  • Fever that persists after taking standard doses of medication
  • Dizziness
  • Confusion
  • Inability to wake up or stay awake
  • Severe weakness
  • Severe muscle pain
  • Extreme vomiting
  • Not urinating
  • Symptoms that improve and then become worse again

Remember that this list is NOT exhaustive. Seek medical attention if you develop any concerning symptoms.

Key takeaways

COVID-19 and influenza have similar symptoms but different causes and treatment options. In addition to this, COVID-19 complications are more frequent and dangerous.

Because both diseases spread in a similar way, you can reduce your risk of both COVID-19 and the flu by following the same precautions: washing your hands, not touching your face, avoiding crowds, wearing a mask, and getting vaccinated (you can even get both vaccines on the same day).

While most cases of COVID-19 and influenza can be treated at home, it’s important to stay in touch with your doctor if you’re in a higher-risk group and seek immediate help if you develop severe symptoms.

January 11, 2023