COVID vs Flu: The Key Symptom Differences You Should Know This Winter Season

Every winter, people start worrying about coughs, fevers, and that familiar wave of body ache. And now, with the winter season still around, it’s become even harder to tell which illness is which. Both COVID and the seasonal flu spread in similar ways and share many symptoms. But they’re not the same infection. They behave differently, progress at different speeds, and require different kinds of care.

To help break things down clearly, we reached out to Dr Pooja Ramesh, Senior Specialist Pulmonologist, Aster RV Hospital, Bangalore, who explained how to spot the differences and when to take symptoms seriously.

Is Loss of Taste or Smell Still the Biggest COVID Clue?

For a long time, suddenly losing taste or smell was the one symptom that almost everyone associated with COVID-19. But as newer variants emerged, that has changed. Dr Ramesh explains, “New loss of taste or smell was once considered one of the most distinctive signs of COVID-19, but it is no longer the most reliable differentiator. With newer variants, this symptom has become less common, and both COVID-19 and influenza now share a wider overlap of presentations.”

She also reminds us that even though symptoms overlap, the two infections are still completely different. “COVID-19 and seasonal flu are not the same thing. Different viruses cause them. Each illness has its own treatment. And each illness can lead to different problems after recovery.”

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How the Symptoms Begin: Slow vs Sudden

One of the clearest ways to tell the difference is how quickly symptoms hit you. According to Dr Ramesh, Flu symptoms appear fast. Many people feel fine in the morning and very sick by afternoon. COVID-19 symptoms appear more slowly, often building over one to three days.

She adds, “The onset of flu is sudden, characterised by chills, a high fever, and deep, sometimes draining body aches. Many patients even remember the exact hour their flu began.”

COVID, on the other hand, usually begins with:

• A scratchy throat
• Gradual fatigue
• Mild congestion
• Cough appearing later rather than at the start
• Loss of taste or smell can still occur, but not as often as before.

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Shortness of Breath: What It Means

Severe shortness of breath is one of the more worrying symptoms people look out for, and COVID is still more likely to cause it. Dr Ramesh says, “COVID-19 can cause significant shortness of breath, especially in older adults or people with underlying health issues. This often appears around day 4–8 of the illness, not usually at the very beginning.”

She explains that the flu can also lead to breathing problems, but usually because of complications like pneumonia, and it’s less common compared to COVID.

How Long Does It Take for Symptoms to Show Up?

• Understanding the incubation period can also help.
• Flu symptoms usually appear 1–4 days after exposure.
• COVID-19 symptoms can appear 2–14 days after exposure.

Dr Ramesh notes that the COVID cough tends to be “dry, continuous, and can last for more than an hour or appear in repeated episodes across a day.”

Quick Symptom Comparison

Here’s a simple cheat sheet to help:

Flu symptoms:

• Sudden onset
• High fever
• Strong body aches
• Severe headaches
• Early cough

COVID-19 symptoms:

• Gradual onset
• Sore or scratchy throat early
• Fatigue is building over days
• Cough appearing later
• Possible loss of taste/smell (less common now)

A recent study published in The Lancet Respiratory Medicine highlighted how overlapping symptoms make clinical diagnosis difficult without testing. But the study noted that COVID-19 continues to show stronger links with breathing issues and prolonged fatigue than the flu.

How to Protect Yourself From Both COVID and the Flu

Dr Ramesh emphasises that preventing these infections still comes down to simple habits done consistently.

1. Get Vaccinated

• “To lower the risk of serious influenza or COVID-19 illness, get the COVID-19 vaccine and the seasonal flu vaccine,” she advises.
• You can take both vaccines in the same visit if they’re due at the same time.

2. Follow basic hygiene and distancing

A few steps go a long way:

• Avoid close contact with sick people.
• Keep space between yourself and others indoors.
• Avoid crowds and poorly ventilated areas.
• Wash your hands for at least 20 seconds.
• Use sanitiser when soap isn’t available.
• Wear a mask in crowded indoor locations.
• Cover your mouth and nose when coughing or sneezing.
• Avoid touching your face.

Dr Ramesh adds, “These steps work best when you do them together.”

When Should You Seek Medical Advice?

Get help if you notice:

• High fever that doesn’t settle
• Trouble breathing
• Persistent chest pain
• Severe fatigue
• Confusion
• A child showing fast breathing or dehydration
• Early evaluation ensures early treatment for either infection.

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Conclusion

COVID-19 and the flu may look similar, but how they start, how fast they progress, and how severely they affect breathing can be very different. Knowing the early clues helps you act faster and protect others. With expert guidance, routine precautions, and timely vaccination, you can stay safer this winter even when symptoms start to overlap.