Flu or COVID-19? What You Need to Know

As we enter the cooler months, respiratory viruses begin to circulate more widely. Two of the biggest on people’s minds: the seasonal flu (influenza) and COVID‑19. While they share many features, they are not the same. Knowing how they differ — and overlap — is critical for prevention, early treatment, and avoiding complications.

What causes them + how they spread

• Flu is caused by influenza viruses (typically types A and B). 

• COVID-19 is caused by the virus SARS‑CoV‑2. 

• Both viruses spread in similar ways: via respiratory droplets when someone coughs, sneezes, talks, or breathes; and via inhalation of smaller aerosol particles, especially in poorly ventilated indoor settings. 

• One key difference: COVID-19 tends to spread more easily and for a longer period than seasonal flu. 

Symptoms: Overlap + distinct features

Overlap

Both flu and COVID-19 can present with:

• Fever or feeling feverish/chills

• Cough

• Sore throat or runny/stuffy nose 

• Fatigue / body aches / headache 

• Occasionally : vomiting or diarrhea (especially in children) 

Key differences

• Onset of symptoms: Flu symptoms typically appear faster — often 1-4 days after infection. COVID-19 may take longer: 2-14 days (or more) to show symptoms. 

• Loss of taste or smell: Much more common in COVID-19 and rare in flu.

• Duration and severity: COVID-19 symptoms often last longer than flu; shortness of breath may develop more frequently or later. 

• Contagious period: COVID-19 may stay contagious longer, including before symptoms appear.

• Bottom line: You can’t reliably distinguish flu vs COVID-19 just by symptoms alone. Testing is critical.

Complications + who’s at risk

• Both illnesses can lead to severe outcomes: pneumonia, exacerbation of chronic diseases (heart/lung), hospitalization, and even death. 

• COVID-19 comes with additional risk of “long COVID” — lingering symptoms and multi-system effects — which is less typical for flu. 

• People at higher risk (for both) include older adults (65+), pregnant women, people with weakened immune systems, chronic health conditions.

Testing, treatment + prevention

Testing

If you’re experiencing symptoms — or have been exposed — testing is the only way to distinguish flu vs COVID-19 (or even co-infection). 

Treatment

• Flu: Antiviral treatments exist (e.g., oseltamivir/“Tamiflu”) that can reduce severity if started early. 

• COVID-19: Has its own antiviral treatments (e.g., nirmatrelvir-ritonavir / Paxlovid) for eligible patients. 

• For both: supporting care — rest, fluids, managing symptoms — remains foundational.

Prevention

• Vaccination remains the number one tool: stay up-to-date with both the flu shot and COVID-19 vaccinations. National Council on Aging+1

• Other preventive measures: hand hygiene, mask wearing in high-risk settings, avoiding crowded poorly ventilated spaces, staying home when sick. 

Practical advice for you and your loved ones

1. If you feel unwell — even with mild symptoms — treat it as potentially serious: isolate, test (for flu and COVID), contact your health care provider if your symptoms worsen.

2. Getting vaccinated: It’s safe to receive flu and COVID-19 vaccines at the same visit; don’t delay.

3. Prevent spreading: If you’re sick, stay home, cover coughs/sneezes, wear a mask when around others especially vulnerable people.

4. High-risk individuals: If you’re older or immunocompromised, seek medical advice early if you catch any respiratory illness — early treatment matters.

5. Don’t assume “just a cold”: Because of symptom overlap and potential for serious complications, err on the side of caution.

Why it matters now

As we move into the fall and winter months, the overlap of flu season and ongoing COVID-19 circulation means health systems and individuals face a dual burden. The risk of co-infection (getting both flu and COVID at the same time) increases complications. Being informed and proactive (vaccines + testing + early care) helps reduce that burden.

In Summary

Flu and COVID-19 may share symptoms, but their impact on health — and on your organization’s productivity — can be very different. During meetings and events, even one contagious attendee can disrupt schedules, lower engagement, and increase medical costs.

At InHouse Physicians, our on-site medical teams help prevent those disruptions through proactive flu and COVID-19 management — from pre-event wellness screenings and vaccination clinics to rapid testing and real-time care when illness strikes.

By planning ahead and integrating medical support into your event strategy, you can keep your attendees healthy, protect your investment, and deliver a safer, more successful experience for everyone.

Ready to safeguard your next meeting? Learn more about IHP’s On-Site Medical and Wellness Programs.