With the recent COVID-19 pandemic, we have a new viral “flu” making its rounds, especially during the changing seasons. With their overlapping symptoms, however, it can be relatively difficult to know whether you have COVID or flu. 

Evolving strains in both influenza and the COVID-19 virus have necessitated being up-to-date on vaccinations. But, as we saw during the pandemic, being vaccinated hasn’t limited the chances of getting infected. It reduces the intensity of symptoms. Having fewer symptoms can actually make your viral illness more of a puzzle when it comes to guessing which infection you may have. 

Therefore, this article will explore the signs you can look out for to be able to differentiate between the flu and COVID-19.

Recognizing Flu Symptoms

When we generally refer to the “flu”, we are talking about the infection caused by the influenza virus. This is also known as seasonal flu as it is frequently observed during the winter months.

According to the World Health Organization, influenza often appears in epidemics in temperate regions during the winter months, while in tropical areas, it can have outbreaks throughout the year¹.

Influenza can affect all age groups. But certain individuals are at a higher risk of severe infection when compared to the rest. Pregnant women, children, adults over the age of 65, those with chronic medical conditions such as kidney disease, asthma, diabetes, and cancer, and those who are immunocompromised are a few groups that fall on this list².

For the most part, however, influenza shows up as a sudden onset of high fever accompanied by a dry cough, malaise (general feeling of being ill), severe body aches, a runny nose, and a sore throat. Flu symptoms might not be severe for those who have strong immune symptoms. A runny nose, mild fever, and body aches might be the only indication of the flu. These symptoms often subside on their own in a week or two. However, the severity of symptoms can be higher among those who have a weakened immune system.

Since, for most, the flu resolves on its own in a couple of weeks with over-the-counter medicines such as paracetamol or cough syrups, many do not get a test. The seasonal flu vaccine also helps to lower the severity of symptoms, reducing the likelihood of ever needing significant medical attention.

Recognizing COVID-19 Symptoms

Some of the initial signs that indicate an underlying COVID-19 infection include a high fever, sore throat, and a dry persistent cough. During the pandemic, a vast majority of individuals had negligible symptoms even during their infective stages. Many were asymptomatic carriers, which was a reason for the easy spread of the virus among communities.

A tell-tale symptom of COVID-19 during the pandemic was a loss or change in smell and taste. But, while a frequently associated symptom of COVID-19, there has been a high variability, between 5–98%, of people who reported an alteration in their smell³.

Among other symptoms, headache, nausea, diarrhea, a sore throat, and shortness of breath have also been recorded as symptoms of COVID.

Similar to influenza, individuals who fell in a high-risk category often presented with more severe symptoms of COVID-19. Patients among whom the most serious respiratory consequences were observed were those with diabetes, kidney disease, lung conditions such as COPD, or who were immunocompromised. Their oxygen saturation was frequently low during their COVID-19 infection and was a parameter to document the respiratory progression of viral infection⁴.

Differentiating COVID-19 vs the Flu

Both viral infections appear to have similar presentations, especially during the initial phases of illness. High fever, sore throat, body aches, and cough are among the first signs of infection for both. 

However, there are distinct clues that can suggest whether you have COVID or the flu⁵.

Both COVID-19 and the flu are spread through respiratory droplets while sneezing, coughing, or even talking. The infectious phase of influenza is usually the first 3–4 days of symptom presentation. This contrasts with COVID-19, where the day just before symptoms begin is the infectious peak.

Influenza infections have a shorter incubation period than COVID-19⁶. Symptoms usually show up a few days following exposure, whereas with COVID-19 it can take up to two weeks before the fever, loss of smell, and respiratory signs are present. 

Coughs with both viral infections are frequently dry and persistent. However, with COVID-19 cough intensity could be worse in patients with severe respiratory involvement, often leaving them gasping for breath. Cough was also a sign of long COVID-19, along with dyspnea, pain, and brain fog⁷.

Loss of smell and taste was characteristically associated with COVID-19 but not the flu. While symptoms like exhaustion, headaches, and body aches are present with both, but appear to be more severe with the flu.

Studies have also indicated that blood work can also differ between patients with COVID-19 and influenza infections. Liver injury, shown by raised liver enzymes and significant decreases in platelets, was likely to be seen among patients with COVID-19 but not the flu⁸.

For both flu and COVID-19, gastrointestinal (GI) symptoms such as diarrhea and vomiting were more prominent among children. With COVID-19 specifically, there has also been documentation of multi-system inflammatory syndrome, where GI symptoms predominate along with a rash, conjunctivitis, and other signs of circulating inflammation⁹.

Conclusion

With life moving back to its normalcy after the COVID-19 pandemic, we expect a new flu virus to circulate during the seasonal outbreaks. With changes in season and fluctuating immunity, co-infection with both influenza and COVID-19 is also possible, especially among those with compromised immune systems¹⁰.

Vaccines are available for both COVID-19 and the flu. Following immunization schedules can reduce the intensity of infection and also reduce spread. Identifying signs early can also prompt early treatment and the use of preventive measures to reduce the spread of both the flu and COVID-19.

Both COVID-19 and the flu spread easily. This means observing hints of either viral illness should prompt a doctor’s visit, especially to prevent severe disease severity.

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Dr. Michelle Frank

Michelle is a healthcare consultant and content creator with over six years of experience in the FemTech space. She contributes extensively to health forums, especially those centered on enabling wellness, advancing digital health, and FemTech solutions. She loves classic rock music, reading classic literature, and finding new spots in town for good food and some chai.