Posted on : September 14, 2023 by Clinic One on COVID-19

In the realm of infectious diseases, two prominent adversaries have been making headlines: Seasonal Flu and COVID-19 Flu. While they share striking similarities in symptoms and transmission, there are critical distinctions that set them apart.

What is Seasonal Flu? 

Seasonal influenza is a contagious illness that is caused by different types of Influenza viruses. Commonly, there are 4 types of influenza viruses responsible for the seasonal flu; Type A, Type B, Type C, and Type D.

It is an infectious disease that can be transmitted through droplets from an infected person even before they get sick.

This can result in an outbreak during any season throughout the year, with the winter season being the most common season for the outbreak.

The signs and symptoms of the seasonal flu include:

  • Cough
  • Runny nose or Rhinitis
  • Fever or chills
  • Weakness and body aches
  • Headache
  • Throat pain or Sore throat

What is COVID-19 flu?

Covid-19 Flu is another contagious disease caused by the family of coronavirus (SARS-COV-2). This disease is also transmitted from an infected person through the spread of droplets. This virus frequently mutates and changes its nature and characteristics.

The signs and symptoms of COVID-19 include:

  • Body aches and weakness
  • Fever and chills
  • Pain in the eyeballs
  • Headache
  • Diarrhea
  • Nausea and vomiting
  • Loss of appetite

Seasonal Flu often gets confused with the COVID-19 Flu because their symptoms and means of transmission are almost the same.

seasonal flu

How can we differentiate between Seasonal Flu and COVID-19 Flu?

1. Virus

The first and foremost difference to be known is the virus responsible for causing each of them.

Seasonal Flu is caused by four different types of Influenza viruses.

  • Influenza Virus (Type A)
  • Influenza Virus (Type B)
  • Influenza Virus (Type C)
  • Influenza Virus (Type D)

Along with its type, there are other strains of Influenza responsible for the outbreaks. Some of the most common strains of Influenza include:

  • H1N1
  • H5N1
  • H3N2 (responsible for causing major outbreaks and severities)

In contrast, COVID-19 is caused by the coronavirus. However, there are multiple variants of this virus with different levels of severity. The different strains of coronavirus are:

  • Alfa
  • Beta
  • Gamma
  • Delta
  • Omicron

2. Incubation Period

Another critical difference is the incubation period of each Flu. An incubation period refers to the time period between the infection and the appearance of the first symptom.

The incubation period of influenza is shorter, i.e. about 1-2 days whereas the incubation period of COVID-19 is usually longer, i.e. about 2-5 days.

3. Signs and Symptoms

Almost every sign and symptom of both the seasonal flu and COVID-19 are too similar. It increases the chances of misdiagnosis. However, the key difference includes:

  • Seasonal flu comes with a runny nose, while COVID-19 might have a stiff nose.

4. Origin

The origin of Influenza is known to have started before 1600 AD. The first influenza outbreak was recorded in 1580 AD, which began in Asia and gradually spread across Africa, Europe, and America during the summer.

The Origin of COVID-19 took place in December 2019, was first recorded in Wuhan, China and gradually spread across the globe. By 2022, 551 million cases had been confirmed in more than 194 countries.

5. Seasonality

The incidence of seasonal flu is seen once or twice a year. It can occur in any season throughout the year, but the winter season is one of the most common reasons for its occurrence.

The Incidence of COVID-19 cannot be predicted but can occur in any season. The trend analysis of its incidence cannot be too reliable as it is a newly discovered disease.

6. Severity

Globally, 5–10% of adults and 20–30% of children get infected with the seasonal flu every year. 5–15% of the global population gets infected by the influenza virus, resulting in 3-5 million cases of illness every year. It accounts for 0.3–0.65 million deaths each year due to respiratory illness (“Influenza,” 2023).

In Nepal, Influenza affects thousands of people every year. Among them, children, the elderly, pregnant women, and immuno-compromised people are mostly affected.

Globally, there are 769,806,130 confirmed cases of COVID-19, with 69 million deaths registered till August 2023, as per the World Health Organization (WHO Coronavirus (COVID-19) Dashboard, n.d.).

In Nepal, There have been more than 1 million confirmed cases of COVID-19, with more than 12000 deaths registered till August 2023, according to the World Health Organization (Nepal, n.d.).

7. Complications

Both the seasonal flu and COVID-19 have similar complications.

Ear infection is a common complication seen in seasonal flu, while a condition called Thrombosis can be found as a complication in COVID-19. Additionally, kidney failure can be a common complication of COVID-19.

8. Prevention

A quadrivalent vaccine against Influenza protects people from 4 strains of the virus. This vaccine is taken every year.
While the COVID Vaccine provides protection against the COVID-19 virus.


The existing difference between seasonal and COVID-19 flu has been mentioned above. An RTC-PCR test can be performed for the appropriate diagnosis. Misdiagnosis or self-diagnosis can sometimes worsen flu symptoms.

Thus, Flu diagnosis is preferred before taking flu medication. However, a diagnosis isn’t necessary for taking a vaccine shot. Early vaccination every year provides both short-term and long-term protection.

Key points

  • Seasonal Flu and COVID-19 Flu are two different Flu caused by two viruses.
  • Seasonal Flu originated before 1600 AD, while COVID-19 recently originated in 2019 AD.
  • Seasonal Flu re-emerges every year, while the re-emergence of COVID-19 cannot be predicted.
  • Seasonal Flu has a shorter incubation period than COVID-19 Flu.
  • The Influenza Vaccine can prevent Seasonal Flu, COVID-19 Flu can be controlled by the COVID-19 Vaccine.


Influenza. (2023). In Wikipedia. 

Nepal: WHO Coronavirus Disease (COVID-19) Dashboard With Vaccination Data. (n.d.). Retrieved August 25, 2023, from 

WHO Coronavirus (COVID-19) Dashboard. (n.d.). Retrieved August 25, 2023, from 

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