With rising cases of viral infections, it is difficult to comprehend the difference between H3N2, COVID and common flu. However, here is a brief to understand the differences backed by experts.

Viral Infections Rise In India: Understanding Difference Between COVID, H3N2 And Flu
Viral Infections Rise In India: Understanding Difference Between COVID, H3N2 And Flu (Freepik)

Drastic season change has stimulated a series of infections. While flu is a common illness that spreads specially when weather changes, this time there have been more. Until a few days back, the new influenza subtype H3N2 was spreading like wildfire and had triggered a wave of panic. And now, another new variant of COVID-19 has emerged that is possibly driving the uptick in the coronavirus cases. Over the last couple of months, the more fortunate among us have been reading about an increase in flu cases, and the less fortunate have got infected and say that this time around, it did not seem like a “normal” flu with prolonged symptoms, especially cough. This is being attributed to H3N2, which many believe to be different from flu.  Recent reports of increasing COVID-19 detections, have intensified the confusion. Now, any symptoms of respiratory infection are leading to uncertainty as to the cause.

Due to overlapping of signs and symptoms, it is very confusing for a layperson to comprehend the difference.  It is therefore essential to understand the symptoms of and the differences between COVID-19 and influenza.


COVID-19 is transmitted through respiratory droplets and the symptoms closely resemble those of other respiratory infections. Symptoms can start 2-14 days after exposure. Common symptoms are fever, cough, and shortness of breath. Individuals could also experience fatigue, muscle pain, headache, loss of taste or smell (less common now), sore throat, congestion or runny nose, nausea or vomiting, and diarrhea.

In vulnerable groups, COVID-19 can be severe and lead to pneumonia, acute respiratory distress and organ failure.


Influenza or the flu is highly contagious and spreads when an infected person’s virus-containing respiratory droplets get transferred to a non-infected person while sneezing, coughing or even talking. They can also spread through commonly touched surfaces.

Once infected, signs and symptoms appear within 1-3 days, often without warning, and vary in severity. The common symptoms are fever, chills, body aches, a runny or blocked nose, headache, and body ache.

Several individuals are experiencing a sore throat and a persistent dry cough. Due to the nature of the H3N2 virus this cough can last for weeks.

A Quick Look At Basic Difference In Symptoms

  •  COVID-19 can cause infections through the year but influenza is more “seasonal”, starting in winter and ending in late spring / early summer
  •  COVID-19 is more common in young adults and older individuals whereas children below 8 years and those above 65 years are more at risk for influenza
  • COVID-19 and influenza can both cause fever, but fever is less common and usually of a lower grade (between 99-101o F) in influenza patients
  • Although cough is present in both conditions, in influenza caused by H3N2, the cough can be severe and takes longer to subside
  • COVID-19 causes profound fatigue which is less common in influenza
  •  COVID-19 can cause a loss of smell or taste, whereas influenza does not
  •  Influenza can cause gastrointestinal symptoms such as nausea, vomiting, and diarrhea, but they are less common in COVID-19
  •  Although both illnesses can lead to complications, but COVID-19 is more likely to cause severe illness, hospitalization and death, particularly in those with existing chronic diseases

While the symptoms can be similar and confusing, laboratory tests like RT-PCR are available for both infections and can definitively identify the virus.

Being aware, seeking information from credible health information sources, masking in crowded indoor and outdoor areas is important. And just as being up to date with COVID-19 vaccines and boosters, availing annual influenza vaccination can help keep you and your loved ones protected.

(- inputs from Dr. Vikram Vora, Medical Director for the Indian Subcontinent at International SOS)

Published Date: March 31, 2023 5:25 PM IST

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