Differences Between the Flu and COVID-19

The annual flu season is about to be in full swing. In the United States, flu season falls between October and March each year, with December, January and February seeing the highest number of flu cases. While the yearly onset of sore throats, runny noses and body aches related to the flu is to be expected to some extent, this year, the COVID-19 pandemic is thrown into the mix.

For the 2019-2020 flu season, the Centers for Disease Control and Prevention (CDC) estimate there were 39 to 56 million flu cases in the U.S. between October 1, 2019 and April 4, 2020. With the current number of confirmed COVID-19 cases surpassing 7 million, the CDC expects both the influenza virus and coronavirus to spread this flu season. This may lead to confusion and worry should you fall ill.

Are your symptoms consistent with influenza? Or are they indicators you’ve been exposed to COVID-19? We’ll break down the differences between symptoms of the flu and COVID-19 as well as what other similarities and differences exist between the two viral diseases so you’re as prepared as possible heading into flu season.

What causes COVID-19 and the flu?

The first difference between COVID-19 and the flu is the virus that causes them. While both illnesses are caused by viruses, the flu is caused by different types and strains of influenza viruses. There are three main types of flu viruses: types A, B and C. Mutations occur within these viruses which lead to different strains. The World Health Organization conducts research each year to predict which strains of influenza viruses are most likely to spread each year.

COVID-19, on the other hand, is caused by a virus belonging to a family of coronaviruses. There are several types of coronaviruses that cause illnesses, such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). The type of coronavirus that causes COVID-19 was identified in 2019 and is known as severe acute respiratory syndrome coronavirus 2, or SARS-CoV-2 for short. 

COVID-19 vs. flu symptoms 

The symptoms resulting from COVID-19 and the flu are similar, which can make it hard to tell the difference between the two based on symptoms alone. If you’re feeling ill and you have symptoms consistent with both COVID-19 and the flu, your physician may conduct testing to confirm the proper diagnosis.

Similarities 

Both COVID-19 and flu can cause varying degrees of symptoms. You may experience no symptoms (called asymptomatic cases) or you could develop severe symptoms.

According to the CDC, symptoms both illnesses commonly share include the following. 

• 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
• Vomiting and diarrhea (most common in children) 

In addition, both COVID-19 and the flu can result in pneumonia, a secondary infection that inflames the air sacs in one or both of your lungs. 

Differences

COVID-19: Many people infected with SARS-CoV-2 don’t feel sick or develop symptoms; however, they can still transmit the virus to others. Unlike the flu, symptoms of COVID-19 can include a new loss of taste (ageusia) or smell (anosmia).

If you develop symptoms of COVID-19, they'll typically develop five days after being infected, but symptoms can appear as early as two days after infection or as late as 14 days following infection. The CDC lists the following as possible symptoms of COVID-19. 

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Fatigue
• Muscle or body aches
• Headache
• New loss of taste or smell
• Sore throat
• Congestion or runny nose
• Nausea or vomiting
• Diarrhea

The Flu: The flu typically comes on suddenly and can cause mild to severe symptoms. Symptoms typically develop one to four days following infection from the influenza virus. According to the CDC, people who have the flu often experience some or all of the following symptoms. 

• Fever or feeling feverish/chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue (tiredness)
• Vomiting and diarrhea (more common in adults)  

How COVID-19 and the flu spread from person to person 

Similarities 

COVID-19 and the flu are spread from person to person in a similar fashion. With both illnesses, it’s possible to spread the virus at least one day before experiencing any symptoms. Even if you haven’t yet developed symptoms, or if you’re an asymptomatic carrier, you can still spread the disease to others without feeling sick. 

Both the influenza virus and SARS-CoV-2 are spread via droplets or smaller virus particles expelled from a sick individual. These droplets can be expelled when you cough, sneeze, talk and breathe. The virus particles can linger in the air, where another person can inhale them and become infected. Wearing a mask can prevent you from spreading the virus to others if you're sick and decrease your risk of inhaling virus particles expelled by others when you’re healthy. Both viruses can also spread on surfaces. If you touch a surface with the virus on it, it’s possible to transfer the virus to yourself by touching your face. This is why it’s important to avoid touching your face and to wash your hands often. 

Differences 

COVID-19: Researchers are still unsure how long someone can spread SARS-CoV-2 to other people after they become infected. Current research says infected individuals can spread the virus for about two days before experiencing symptoms. If you’re asymptomatic or have had symptoms that have since gone away, it’s possible to remain contagious for at least 10 days after testing positive for COVID-19, according to the CDC. 

The flu: You’re typically contagious for about one day before developing symptoms. Older children and adults are most contagious during the first three to four days of being sick but can remain contagious for up to seven days. Infants and those with weaker immune systems can be contagious for even longer. 

Treatment options 

Similarities

Since viruses cause both the flu and COVID-19, antibiotics, which can only be used to treat bacterial infections, won’t help your recovery. Both illnesses are typically treated by addressing symptoms, such as reducing fever with acetaminophen (Tylenol).

Most people who become ill with the flu and COVID-19 can recover at home. For minor symptoms associated with both illnesses, getting rest, staying hydrated and taking medications to reduce fever and aches and pains can offer relief.

Differences 

COVID-19: If you're sick, follow the CDC’s guidelines for preventing the spread of COVID-19. Treatments for COVID-19 are currently being tested. Therapies under investigation include antiviral medications designed to treat other viruses (remdesivir), corticosteroids such as dexamethasone and antibodies obtained from the convalescent plasma of those who have recovered from COVID-19. You can read more about current treatments being investigated here. 

The flu: Oral antiviral medications can address symptoms and shorten the duration of the flu. Your physician can prescribe antivirals as necessary. Antivirals that are approved by the FDA for treating influenza include oseltamivir phosphate (available under the name Tamiflu), zanamivir (Ralenza), peramivir (Rapivab) and balaxavir marboxil (Xofluza).

Prevention 

Similarities

COVID-19 and the flu can be prevented by wearing a mask, washing your hands frequently and thoroughly, coughing into your elbow, staying home when you're sick and limiting contact with people who are infected.

Differences

COVID-19: There is currently no vaccine to prevent COVID-19. Vaccine developers and other researchers and manufacturers are expediting the development of a vaccine.

The flu: The annual flu vaccine is effective in preventing or reducing the duration of the flu. It’s important to get your flu shot annually as the vaccines are adjusted each year to protect against the three or four flu virus strains anticipated to circulate that year. 

If you develop symptoms consistent with COVID-19 or the flu or believe you may have been exposed, contact your health care provider as soon as possible to discuss your situation. They can recommend any necessary testing as well as possible treatment options.