Can You Have COVID-19 and Flu at the Same Time?

With COVID-19 and flu both circulating through the colder months, it's a fair question: can you actually catch both at once? The answer is yes, though genuine co-infection is relatively uncommon and there's a growing set of tools designed specifically to tell the two apart when it matters.

Is catching both at once common?

According to the CDC, co-infections with SARS-CoV-2 and influenza can occur but aren't common. Documented cases exist, including instances where a person tested negative for one virus but positive for the other on initial testing, which highlights part of the diagnostic challenge involved. Most of the time, a respiratory illness during winter turns out to be one virus or the other rather than both simultaneously.

Why it's hard to tell them apart by symptoms alone

COVID-19 and flu share a strikingly similar symptom profile: fever, cough, sore throat, fatigue, body aches and headache can all appear with either illness and sometimes both together. This overlap is exactly why symptom-based self-diagnosis is unreliable and why testing has become the standard way to distinguish between them, particularly for anyone at higher risk of complications from either virus or who's in close contact with someone vulnerable.

How co-infection is actually tested for

Multiplex tests, which check for multiple viruses from a single sample, have become widely available and can detect influenza A and B alongside SARS-CoV-2, with some versions also covering RSV. Some multiplex antigen tests are available over the counter for home use, while multiplex nucleic acid tests offer higher sensitivity through a healthcare provider or laboratory. Where multiplex testing isn't available, a standard SARS-CoV-2 antigen test combined with a separate influenza nucleic acid test can achieve a similar result.

Why distinguishing between them matters

Getting an accurate diagnosis affects treatment decisions directly. Antiviral medications for influenza and antivirals for COVID-19 are different and using the right one, or knowing both viruses are present, can meaningfully affect clinical management, particularly for people in higher-risk groups who may benefit from early antiviral treatment. Accurate testing data also feeds into public health surveillance, helping track how flu and COVID-19 are spreading through the population during a given season.

Is co-infection more dangerous than either virus alone?

This remains an area researchers continue to study and the honest answer is that a definitive, universally applicable conclusion isn't yet settled. Logic and some case evidence suggest a co-infection could plausibly place more strain on the body than either illness individually, particularly in people with underlying health conditions, but this hasn't been established as a certainty for the general population. Regardless, anyone experiencing a co-infection or a particularly severe presentation of either virus alone should seek medical advice.

Protecting yourself against both

The UK's Autumn/Winter COVID-19 booster programme is deliberately timed to run alongside the seasonal flu vaccination programme and co-administration, receiving both vaccines at the same appointment, is generally offered where possible for eligible groups. Getting both seasonal vaccines, rather than just one, is the most direct way to reduce your risk of either infection and by extension, the small but real possibility of catching both together.

What to do if you suspect you have both

If you're testing positive for one virus but your symptoms seem more severe or prolonged than expected, or you have specific reason to suspect co-infection, for example known close contact with people carrying both viruses, a multiplex test or separate tests for each virus can clarify the picture. Managing symptoms at home with rest and fluids applies regardless of which virus, or viruses, are involved, though anyone in a higher-risk group should contact their GP promptly given the potential for either illness to affect them more seriously.

Getting tested in the UK

Free NHS testing for the general public largely ended in 2022 and most people now buy lateral flow tests, including multiplex versions covering flu, from pharmacies. The NHS testing guidance outlines when testing is most useful, generally before visiting someone vulnerable or when symptoms are severe enough that knowing the specific cause would change how you manage them.

What this means heading into winter

As both viruses circulate simultaneously through the colder months, being aware that co-infection is possible, even if uncommon, is a useful piece of context rather than something to worry about excessively. The practical response stays the same regardless: test if it matters for your situation, stay home while unwell and get both seasonal vaccines if you're eligible, since that remains the most effective way to reduce your risk of either illness.

A note for higher-risk groups

People in clinical risk groups, including older adults and those with underlying respiratory or cardiovascular conditions, may benefit most from prompt testing if they develop symptoms during winter, since knowing which virus or viruses are involved can guide faster access to antiviral treatment where eligible. Speaking to a GP or pharmacist early in an illness, rather than waiting to see how symptoms develop, is generally the more cautious approach for anyone in this position.

Ultimately, the small possibility of co-infection is one more reason not to assume a respiratory illness during winter is automatically "just a cold," particularly if symptoms feel more severe than usual or you're in a higher-risk group yourself.

A note on RSV too

RSV is a third respiratory virus that circulates heavily during winter alongside flu and COVID-19 and some multiplex tests now cover all three at once. While RSV is generally most concerning for young children and older adults, its presence in the same testing panels reflects just how much winter respiratory illness overlaps in symptoms, timing and, occasionally, in who ends up catching more than one at once.

A quick recap

Catching COVID-19 and flu at the same time is possible but uncommon and because the two illnesses share so many symptoms, testing rather than guesswork is the reliable way to tell them apart. Multiplex tests covering both viruses, alongside RSV in some cases, have made this considerably easier and getting both seasonal vaccines remains the most effective way to reduce your risk of catching either.

Frequently asked questions

Can one test detect both COVID-19 and flu?

Yes, multiplex tests designed to detect influenza A, influenza B and SARS-CoV-2 from a single sample are widely available, including some over-the-counter antigen versions for home use.

Is it safe to get the flu jab and COVID-19 booster together?

Yes, co-administration of both vaccines at the same appointment is generally considered safe and is commonly offered during the UK's Autumn/Winter vaccination programme for eligible groups.

Do you need to isolate longer if you have both viruses?

There's no specific extended isolation requirement for co-infection in the UK. General guidance to stay home while feverish or unwell applies regardless of which virus, or viruses, are responsible.

Can children get COVID-19 and flu together?

Yes, children can be co-infected in the same way adults can, though as with adults this remains relatively uncommon. Multiplex testing can help clarify what's causing a child's symptoms if needed.

Are symptoms worse with a co-infection?

This isn't firmly established either way in current research. Some case evidence suggests it could place more strain on the body, but this hasn't been confirmed as a general rule and individual experiences vary.