FAQ: COVID-19 & the Flu

Every year, millions of Americans get the flu, a respiratory illness that causes cold-like symptoms that can range from mild to very severe. This year’s flu season is especially unique as it intersects with the coronavirus pandemic, which can cause similar symptoms with a range of severity.

So how can you tell the difference between the flu and COVID-19? When should you get your flu shot? Will the flu shot help protect you from the coronavirus?

Kathryn Bowman, MD, Jennifer Reedy, MD, PhD and Jacob Lazarus, MD, PhD, in the Infectious Diseases Division at Massachusetts General Hospital, answer questions about what to expect from the flu this year and what precautions you should take.

What is the flu?

The flu is a contagious respiratory illness caused by a virus called influenza. It can cause mild to severe illness. There are two main types of influenza virus: Types A and B. These viruses routinely spread in people and are responsible for seasonal flu epidemics each year. Some symptoms of the flu include:

• fever or feeling feverish/chills
• cough
• sore throat
• runny or stuffy nose
• muscle or body aches
• headaches
• fatigue (tiredness)

Serious outcomes of flu infection can result in hospitalization or death. Some people—such as older people, young children and people with certain health conditions—are at high risk of serious flu complications. 

The best way to prevent flu is by getting vaccinated each year.

What does the flu shot protect against?

There are many benefits to getting the flu shot (also called the influenza vaccine). First, it can prevent you from getting sick with the flu for the upcoming season. Second, even if you still contract the flu, it can prevent severe complications and hospitalization. Studies have shown that people who receive the flu shot tend to have less severe illness compared to those who do not. Third, the flu shot helps protect more vulnerable people around us by decreasing the likelihood that the influenza virus is transmitted from person to person.

The flu virus can change from year to year. A new flu vaccine is developed every year to target the versions of the flu virus that are circulating during the current year. So, it is important to get a flu shot every year.

The CDC website includes more helpful information about the benefits of the flu shot.

When is flu season? When is the best time to get your flu shot?

Influenza can occur year-round in the U.S., but it is most common during the fall and winter, which is known as the “flu season.” The flu season can vary from year to year, but it most often peaks between December and March, when there is the most flu activity in the community.

The flu shot works by building up your body’s immunity against the circulating strains of influenza virus. It is most useful when taken early in the flu season. It is recommended to get the flu shot once it is available, usually September and October. However, even if you delay getting the flu shot into the winter, it is still beneficial.

Why is it so important to get the flu shot this year?

The viruses that cause the flu and COVID share some similarities in how they spread from person-to-person. They also share many of the same symptoms: cough, fever, headache, fatigue, muscle aches, runny nose, etc. According to the CDC:

“It’s likely that flu viruses and the virus that causes COVID-19 will both spread this fall and winter. Healthcare systems could be overwhelmed treating both patients with flu and patients with COVID-19. This means getting a flu vaccine during 2020-2021 is more important than ever. While getting a flu vaccine will not protect against COVID-19, there are many important benefits, such as: Flu vaccines have been shown to reduce the risk of flu illness, hospitalization, and death. Getting a flu vaccine can also save healthcare resources for the care of patients with COVID-19.”

Are the flu and coronavirus similar viruses?

The viruses that cause the flu (influenza) and COVID-19 (SARS-CoV2) are different viruses. However, they are both contagious respiratory illnesses with many of the same symptoms. It is hard for a doctor or patient to tell the difference between the flu and COVID-19 without a test.

There are key differences between the flu and COVID-19:

• Sensory loss: Some patients with COVID-19 lose their sense of smell and taste. This does not happen to everyone, but it suggests that COVID-19 is more likely
• Ability to spread: There are differences between the flu and COVID-19 in how long a person can spread the infection to close contacts. Flu symptoms usually develop one to four days after infection. Symptoms from a COVID-19 infection usually develop five days after infection but can appear as early as two days or as late as 14 days after infection
• Treatment options: Most importantly, the treatment for these two infections are very different. People with confirmed flu may receive prescription anti-viral drugs against influenza that can shorten the duration of symptoms and prevent severe complications (these drugs are not effective against COVID-19). Treatment for COVID-19 is tailored to the severity of infection and are constantly being updated as new information is becoming available 

The CDC website includes an easy-to-read description of the similarities and differences between these two infections.

If you have any of the symptoms of a viral respiratory illness this year (such as cough, fever, runny nose, fatigue and muscle aches), it is important to tell your doctor and do not assume that you have either flu or COVID-19 since the treatments may be different.

Will the flu shot protect me from COVID-19?

The flu shot will not protect you from COVID-19 because these infections are caused by different viruses. There are studies investigating potential vaccines for COVID-19 but they are not yet ready for use at the time of this writing. However, there are other preventive measures to take that can protect against both infections:

• Keep your distance from other people
• Wash your hands frequently with soap and water or hand sanitizer
• Stay home if you are feeling sick and encourage others around you to do the same
• Wear a mask in public, especially when indoors and around many other people

Can you have COVID and the flu at the same time?

Yes. There is limited scientific and medical data to tell how often this will occur, but since both of these infections have the potential to cause severe symptoms, it is crucially important to do all you can to prevent the spread of COVID and the flu.

If I feel sick, how do I know if it is flu or COVID?

Since the symptoms of the flu and COVID-19 are similar it can be difficult, if not impossible, to tell the difference between the two illnesses without a test. Therefore, if you have symptoms of a viral respiratory infection (cough, fever, headache, sore throat, runny nose, fatigue and muscle aches), it is important to contact your doctor for advice and to arrange testing, if appropriate.

How can I tell the difference between a cold and COVID?

The symptoms of a common cold and COVID-19 can also be very similar. Symptoms like fever, cough, muscle aches, runny nose, headache and fatigue are common to both infections. It may be very difficult to tell the difference between the common cold and COVID. We recommend speaking to a health care professional, like a primary care doctor, if you experience these symptoms.

If I feel like I am getting a cold during flu/COVID season, when should I reach out for medical help?

If you develop any symptoms of a respiratory viral infection, you should call your doctor’s office for advice and possibly testing. It can be important to make a diagnosis early for several reasons:

• If you have influenza and are at risk for complications due to underlying medical problems, you can be prescribed an antiviral medication. This medication works best if taken within the first few days of illness 
• If you do have COVID-19, it is important to know so that you can isolate yourself appropriately and you can be monitored in case your symptoms worsen. Since new treatments are constantly being adopted for COVID-19, there may be early treatment options available
• Finally, since people with COVID-19 can spread the virus for several days before they develop symptoms, the only way to control the virus is to identify people with the virus and those who may have been exposed, so that they can be tested early or isolated to prevent further spread (this is called contact tracing and is often performed by the Department of Public Health)  

What groups are high priority for the flu shot?

According to the CDC, everyone six months of age and older should get a flu vaccine every season with rare exceptions. Some vaccines are not recommended in some situations and for people with certain health conditions. Some people with certain egg allergies may be allergic to the flu vaccine. The CDC includes more detail on who should get the flu shot.

Is it safe to go out in public to get the flu shot?

Yes, if you follow physical distancing guidelines and wear a mask. Doctor’s offices, hospitals, pharmacies and urgent care clinics have put precautions in place to protect both patients and staff within their facilities. Anytime you go out in public, you should wear a mask. Additionally, you should keep six feet between you and other people, avoid touching your face and frequently wash your hands with soap and water and use hand-sanitizer (particularly before/after removing your mask, before touching your face/eyes/mouth and before eating and drinking). If you are concerned, call the location where you want to get your flu shot and ask about their procedures. Many places have special hours for older individuals or those that are at higher risk. 

In other parts of the world, there has been a mild flu season. Will that be the same for the U.S.?

At this time, it is difficult to know whether the U.S. will have a mild flu season. The precautions to protect against COVID-19 are also effective at decreasing transmission of the flu (physical distancing, masks, frequent hand washing/hand sanitizer use and staying home when sick). Therefore, the hope is that this will be a milder flu season than prior years. Additionally, widespread use of the flu vaccine can further decrease the severity of the flu season.

If a person has had COVID-19, should they still get the flu shot?

Yes. It is safe to get the flu vaccine after recovery from COVID-19.