Influenza—most commonly referred to as the flu—is a respiratory illness that is viral, meaning it can’t be treated with antibiotics. There are many myths surrounding the flu—for example, Jill Grimes, MD, a board-certified family physician and author of The Ultimate College Student Health Handbook stresses that the flu shot does not cause the flu—so we’ve rounded up what you should know about how long the flu is contagious so you can protect your family this year. Here’s everything you need to know.
Stages of the flu
Once you get the flu, it can feel like it lasts forever. While the illness itself may not last long, the fatigue that may follow it can prolong a full recovery. Before you even feel sick, however, the virus is present and that means one thing: You’re contagious. “The period between exposure to a person with flu and development of flu in the exposed person—termed the incubation period—is on average two days,” explains Sherif Mossad, MD, an infectious disease specialist at Cleveland Clinic. “Onset of the illness is sudden, with fever, headache, muscle aches, generalized weakness and dry cough, which [can] last between two and five days [or] up to a week.” This means that there is an incubation period followed by onset, both of which can overlap with a period of contagion. From there, once symptoms have subsided, you may experience fatigue, which Dr. Mossad notes can last for several weeks.
How long is the flu contagious?
As stated, even before flu symptoms set in, you are contagious. Because onset is usually a few days after exposure, you aren’t contagious for very long before you may know you have the flu. Both Dr. Grimes and Dr. Mossad note you are usually contagious for about a day before symptoms develop, but that doesn’t mean others are in the clear once the fever and aches set in. “[The] flu is contagious for about a week, starting a day before you have symptoms,” adds Dr. Grimes, “and maximally contagious for the first 4-5 days that you are sick.” The CDC specifies maximum contagion from three to four days of onset, so using three to five days as a general guideline is ideal. They note that it most commonly spreads from person to person through droplets in the air that can travel up to about six feet (sound familiar?), and less frequently, can be passed from contaminated surfaces. The biggest takeaway is that you are contagious both before and during the onset of symptoms, if you even experience symptoms at all.
How long do flu symptoms last?
We’ve thrown lot of numbers at you, so the general guidelines when it comes to answering the question, how long does the flu last? is that it’s about a week. Commonly, the onset of symptoms will be sudden and last for roughly a week, with a persistent cough or fatigue that can last for weeks after other symptoms resolve. The CDC notes that the most common symptoms of the flu are:
Fever or feverish/chillscoughsore throatrunny or stuffy nosemuscle or body achesheadachesfatigue (tiredness).
These symptoms are not mutually exclusive, however, and fever may not always be present. Dr. Mossad notes that there are other symptoms to look for based on age. “Children may also have vomiting and diarrhea and older adults may predominantly have dizziness and poor appetite,” he specifies. The flu is often confused with the common cold, primarily due to some commonality between symptoms, including cough and sore throat. While the common cold is also a respiratory illness, the CDC specifies that symptoms alone don’t serve as an accurate distinguisher between the two. Testing must often be done to determine whether or not your illness is the flu, which can be helpful to diagnose as the flu can come with greater health complications—such as pneumonia—than the common cold.
How long does the flu truly last?
If considering the time from incubation to complete resolution of all symptoms, the flu can last a few weeks. However, the time between onset and the majority of symptoms is roughly between a week up to a week-and-a-half. This timeline can be a bit skewed in our minds because of the flu shot; particularly due to the myth that the flu shot results in the flu. While there are common side effects, such as low-grade fever and headache, you can rest assured this is not actually the flu itself. “It cannot [give you the flu], because it is a killed virus vaccine; no live “flu” in there,” reveals Dr. Grimes. “Mild aches or low fever after the flu shot are actually a good sign that your immune system is revving up to fight the flu if you are exposed.” Both Dr. Grimes and Dr. Mossad stress the importance of getting the flu shot, especially this year. While it won’t keep every virus at bay, it will help reduce the severity of symptoms, should you be exposed to the flu. Just as flu symptoms overlap with those of the common cold, the symptoms many experience with COVID-19 can also be similar. Just as we are advised to do what we can to stop the spread of the coronavirus, getting the flu shot is the way to stop the spread of the flu. “By getting vaccinated for flu, you’re also protecting your loved ones and those around you by lessening the amount of flu that’s spread in the community,” concludes Dr. Mossad. Next up, read up on ways to boost your immune system during flu season.
Sources
Jill Grimes, MD, a board-certified family physician and author of The Ultimate College Student Health HandbookSherif Mossad, MD, an infectious disease specialist at Cleveland Clinic
