As COVID-19 pandemic continues across the globe, many researchers are consistently researching to understand every detail regarding the Coronavirus. Previously there have been outbreaks with similar symptoms and many comparisons are being made with influenza, commonly known as flu. Both the Coronavirus as well as the Influenza virus cause respiratory illness. However, there are significant differences between COVID-19 and flu, particularly in the rate at which both these infections spread, death rate and whether they affect children or adults more.

In India, the Influenza season usually starts around July to September. It is natural for us to wonder whether the flu symptoms we might be having are due to Coronavirus. Through this article, we shall learn more about the differences between Coronavirus and Influenza.

What is Coronavirus disease (COVID -19)?

In December 2019, a novel virus emerged causing respiratory illness such as fever with cough, sore throat, and breathing difficulty in Wuhan city, Hubei province in China. Studies conducted revealed that the illness was caused by a Coronavirus named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). There had been similar outbreaks of the Coronaviruses in the past like SARS (Severe Acute Respiratory Syndrome) in 2002 and MERS (Middle East Respiratory Syndrome) in 2012.

What is Influenza?

Seasonal Influenza, commonly known as flu, is a respiratory illness caused by two main types of influenza viruses – type A and type B. Influenza A virus is usually present in birds and occasionally spreads to human beings causing a mild to severe respiratory illness. H1N1 is an example of Influenza A virus that caused a pandemic in 2009. However, the Influenza B virus causes relatively milder illness when compared to the Influenza A virus.

A typical outbreak of the Influenza virus begins in early winter and lasts four to five weeks in the affected community, though the duration may vary due to multiple factors. The factors that affect the duration of illness include the number of high-risk people present in a community, the number of people who are vaccinated with the influenza vaccine, and temperate or tropical climate. In a tropical climate, the Influenza virus may occur throughout the year with frequent outbreaks while in temperate regions, outbreaks are mainly seen in the winter season. As per WHO, around 30 to 50 lakh people are affected by the flu globally every year. There has been a significant increase in the number of influenza-like illnesses since the outbreak of COVID-19. However, many of these illnesses may be caused by Coronavirus and not the flu virus.

Are there any similarities between Influenza and Coronavirus?

Initial symptoms of Influenza and COVID–19 are similar to some extent. In both the illnesses, people may experience high fever with cough and sore throat. However, there are many research studies currently underway on the symptoms of Coronavirus as it is a relatively new disease as compared to flu.

Most people with Influenza may have a dry cough lasting two or more weeks, accompanied by headache, and muscle/joint pains. Symptoms like vomiting, nausea, and diarrhoea are commonly observed in children. Typically, children, elderly people, pregnant women, and people with previously existing medical conditions are at higher risk of developing a severe illness due to Influenza.

On the other hand, in the early stages of COVID-19, one might have lesser or no symptoms. The symptoms may appear late and may include dry or wet cough, redness of eyes, congestion of nose, chills, headache, weakness, and loss of taste and smell. The infected person may develop breathing difficulty gradually and may require being admitted to the hospital. Elderly and people with previous co-existing medical conditions like heart disease, lung disease, diabetes, and cancer are at higher risk of developing a severe illness such as pneumonia, multi-organ failure, and in some cases, death.

Both Coronavirus and the Influenza virus are similar in their modes of transmission. This means that both viruses spread through respiratory droplets and contact transmission. Respiratory droplet transmission occurs when a sick person coughs or sneezes and infects a person nearby. Contact transmission occurs when a person touches surfaces contaminated by these droplets.

Due to their similarity in the modes of transmission, the preventive measures for both the Coronavirus and Influenza are also similar. The measures that can curb the transmission of both these viruses include frequent hand washing using either soap water or alcohol-based hand sanitizer, using disposable paper tissue for coughing, social distancing, and regular sanitization of the home and office premises.

What are the differences between COVID-19 and Influenza?

Influenza symptoms come suddenly and patients usually recover in less than 2 weeks. However, based on the data currently available, COVID-19 is said to have a gradual progression into severe disease.

The speed of transmission is a crucial difference between these two viruses. Past data on Influenza and currently transient data on COVID–19 suggest that Influenza can spread faster than Coronavirus. Furthermore, a person with Influenza can shed the virus in the first three to five days of illness before the appearance of symptoms adding to transmission. A person with Coronavirus is also known to shed the virus one to two days before the start of symptoms but this does not appear to be a major cause for transmission.

Since limited data is available on COVID-19, making its comparison with Influenza is difficult. However, the data available shows that the rate of a sick person infecting a healthy person is higher in COVID–19 than influenza.

What is the difference in transmission rate for COVID-19 and Influenza in children?

Influenza mostly affects younger people; children are considered as the drivers for transmission in the community. However, Coronavirus has shown a lesser transmission rate in children. A recent study was conducted on the household transmission of Coronavirus in China. It showed that in a close environment like a house where every person had similar chances of exposure to the Coronavirus, adults are infected more than children.

What is the difference in the severity of illness between COVID-19 and Influenza?

Early studies on Coronavirus have revealed that 80% of infections are mild or asymptomatic, 15% are severe requiring hospital admission, and 5% are critical which means that mechanical ventilation is needed. These numbers of severe and critical illness are higher in COVID-19 as compared to influenza. Severe or critical illness caused by both Influenza and Coronavirus is likely to occur in the high-risk groups which include the elderly, people with a previous medical condition, and with depressed immunity. However, Influenza is also known to cause severe illness in children and pregnant women.

While we await more data on death rate for Coronavirus patients, it is currently in the range of three to four per cent of total patients. Influenza usually has a much lower death rate of 0.1 per cent or below.

A study was done in the United Kingdom to know the difference in probable one-year death rate pre-COVID and post COVID in people with existing medical conditions. The study found that there was a substantial increase in probable death rate after the Coronavirus infection. This implies the importance of high-risk people to follow preventive measures to decrease the risk of contracting the virus.  

Summary

• Influenza and Coronavirus have similar symptoms. However, flu symptoms generally occur faster than Coronavirus symptoms.
• Influenza is known to mainly affect children while Coronavirus mainly affects adults.
• Severe illness is observed more in patients infected with Coronavirus rather than those infected with Influenza.

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