Coronavirus disease (COVID-19): Similarities and differences with influenza


As the COVID-19 outbreak continues to evolve, comparisons have been drawn to influenza. Both cause respiratory disease, yet there are important differences between the two viruses and how they spread. This has important implications for the public health measures that can be implemented to respond to each virus.

What is influenza?
The flu is a highly contagious common illness caused by the influenza virus. Symptoms include fever, headache, body aches, runny nose, sore throat, cough, and fatigue that come on quickly. While most healthy people recover from the flu in about a week, children, the elderly, and people with weakened immune systems or chronic medical conditions are at greater risk of serious complications, including pneumonia and even death. 

Two types of influenza viruses cause illness in humans: types A and B. Each type has many strains that mutate often, which is why people continue to come down with the flu year after year—and why flu shots only provide protection for one flu season. You can get the flu at any time of the year, but in the United States, flu season peaks between December and March. 

Difference between Influenza (Flu) and COVID-19?
1.Signs and Symptoms

Both COVID-19 and flu can have varying degrees of signs and symptoms, ranging from no symptoms (asymptomatic) to severe symptoms. Common symptoms that COVID-19 and flu share include:

● Fever or feeling feverish/chills
● Cough
● Shortness of breath or difficulty breathing
● Fatigue (tiredness)
● Sore throat
● Runny or stuffy nose
● Muscle pain or body aches
● Headache
● Some people may have vomiting and diarrhea, though this is more common in children than adults


Flu:Flu viruses can cause mild to severe illness, including common signs and symptoms listed above.

COVID-19:COVID-19 seems to cause more serious illnesses in some people. Other signs and symptoms of COVID-19, different from flu, may include change in or loss of taste or smell.

2.How long symptoms appear after exposure and infection
For both COVID-19 and flu, 1 or more days can pass between a person becoming infected and when he or she starts to experience illness symptoms.

If a person has COVID-19, it could take them longer to develop symptoms than if they had flu.

Flu:Typically, a person develops symptoms anywhere from 1 to 4 days after infection.

COVID-19:Typically, a person develops symptoms 5 days after being infected, but symptoms can appear as early as 2 days after infection or as late as 14 days after infection, and the time range can vary.

3.How long someone can spread the virus
Similarities:For both COVID-19 and flu, it’s possible to spread the virus for at least 1 day before experiencing any symptoms.

Differences:If a person has COVID-19, they may be contagious for a longer period of time than if they had flu.
Most people with flu are contagious for about 1 day before they show symptoms.
Older children and adults with flu appear to be most contagious during the initial 3-4 days of their illness but many remain contagious for about 7 days.
Infants and people with weakened immune systems can be contagious for even longer.
How long someone can spread the virus that causes COVID-19 is still under investigation.
It’s possible for people to spread the virus for about 2 days before experiencing signs or symptoms and remain contagious for at least 10 days after signs or symptoms first appeared. If someone is asymptomatic or their symptoms go away, it’s possible to remain contagious for at least 10 days after testing positive for COVID-19.

4.How it Spreads
Both COVID-19 and flu can spread from person-to-person, between people who are in close contact with one another (within about 6 feet). Both are spread mainly by droplets made when people with the illness (COVID-19 or flu) cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.

It may be possible that a person can get infected by physical human contact (e.g. shaking hands) or by touching a surface or object that has virus on it and then touching his or her own mouth, nose, or possibly their eyes.
Both flu virus and the virus that causes COVID-19 may be spread to others by people before they begin showing symptoms, with very mild symptoms or who never developed symptoms (asymptomatic).


While COVID-19 and flu viruses are thought to spread in similar ways, COVID-19 is more contagious among certain populations and age groups than flu. Also, COVID-19 has been observed to have more superspreading events than flu. This means the virus that causes COVID-19 can quickly and easily spread to a lot of people and result in continuous spreading among people as time progresses. 

What medical interventions are available for COVID-19 and influenza viruses?

While there are a number of therapeutics currently in clinical trials in China and more than 20 vaccines in development for COVID-19, there are currently no licensed vaccines or therapeutics for COVID-19.  In contrast, antivirals and vaccines available for influenza. While the influenza vaccine is not effective against COVID-19 virus, it is highly recommended to get vaccinated each year to prevent influenza infection. 

5.People at High-Risk for Severe Illness


Both COVID-19 and flu illness can result in severe illness and complications. Those at highest risk include:

● Older adults
● People with certain underlying medical conditions
● Pregnant people


The risk of complications for healthy children is higher for flu compared to COVID-19. However, infants and children with underlying medical conditions are at increased risk for both flu and COVID-19.


Young children are at higher risk of severe illness from flu.


School-aged children infected with COVID-19 are at higher risk of Multisystem Inflammatory Syndrome in Children (MIS-C), a rare but severe complication of COVID-19.

Both COVID-19 and flu can result in complications, including:

● Pneumonia
● Respiratory failure
● Acute respiratory distress syndrome (i.e. fluid in lungs)
● Sepsis
● Cardiac injury (e.g. heart attacks and stroke)
● Multiple-organ failure (respiratory failure, kidney failure, shock)
● Worsening of chronic medical conditions (involving the lungs, heart, nervous system or diabetes)
● Inflammation of the heart, brain or muscle tissues
● Secondary bacterial infections (i.e. infections that occur in people who have already been infected with flu or COVID-19)



Most people who get flu will recover in a few days to less than two weeks, but some people will develop complications, some of these complications are listed above.


Additional complications associated with COVID-19 can include:

● Blood clots in the veins and arteries of the lungs, heart, legs or brain
● Multisystem Inflammatory Syndrome in Children (MIS-C)

Post time: Dec-08-2020

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