What Is the Incubation Period for the Flu This Year?

In the United States, flu season typically starts in October and peaks in February. Health experts are predicting that the 2022–2023 flu season could be more severe than the last couple of years when COVID-19 precautions helped lessen the burden of influenza.

That said, a bad flu season is not completely different from a typical one. While it’s true different flu strains go around from year to year (and some are “worse” than others), there are some aspects of the flu that tend to be consistent in any flu season.

One example? The incubation period for the flu. Dean Winslow, MD, a professor of medicine in the Divisions of Hospital Medicine and Infectious Diseases at Stanford University, told Verywell that the incubation period is the time from when a person is exposed to the flu virus to when they start to have symptoms.

According to Winslow, the flu’s incubation period is 1 to 4 days with an average of 2 days, and it shouldn’t be different year to year.

Winslow also explained that the incubation period for the flu and COVID do not seem to vary much depending on the strain. What can vary is how sick people get—and we’ve seen that with both the flu and COVID.

Why Does Flu Incubation Time Matter?

It’s hard for experts to predict which flu strains will be the most prominent during a given season, but understanding the incubation period helps them guide the public in preventing severe illness, decreasing symptoms, and slowing the spread of the virus.

Infectious disease experts use incubation periods in the surveillance, control, and setting of quarantine guidelines for contagious illnesses like the flu, COVID, and even the common cold.

According to the Centers for Disease Control and Prevention (CDC), the flu incubation period is typically consistent across all strains, but the periods of contagiousness can vary depending on a person’s age and risk factors:

• People with the flu are most contagious 3 to 4 days after becoming ill
• Some healthy adults are able to spread the flu one day before the start showing symptoms and for up to seven days after the illness begins
• Children and people with weakened immune systems might be able to infect others for longer than the typical contagious period

Can You Interrupt the Flu Incubation Period?

In some cases, there are steps you can take in the time between when you were exposed to the flu virus but haven’t started to feel sick yet that could make a difference in how the illness plays out.

For example, Winslow said that certain at-risk people—such as older adults in nursing homes where a flu outbreak is happening—“can be given prophylactic antiviral medications such as Tamiflu (oseltamivir) or Xofluza (baloxavir).”

According to Winslow, these medications are “most effective if given earlier in the incubation period,” but they can still help with “reducing the severity of infection and duration of symptoms even if given in the first 48 hours after symptoms have started.”

The CDC lists four antivirals available to treat suspected or confirmed cases of uncomplicated flu symptoms and also decrease illness severity:

• Oral oseltamivir (Tamiflu)
• Inhaled zanamivir (Relenza)
• Intravenous peramivir (Rapivab)
• Oral baloxavir (Xofluza) 

Getting your annual flu vaccination can also interrupt the incubation period and reduce your chances of needing medical care if you do get sick by 40% to 60%. 

Why Is This Year’s Flu Season Going to Be Worse?

The last two years were comparatively mild flu seasons, but that’s not what we’re expecting this year. The U.S. tries to make predictions about the upcoming flu season by reviewing the severity of the flu season in the Southern Hemisphere, which runs from June to September. According to early reports, this year was Australia’s worst flu season in five years.

There are several factors that can make a flu season more severe, including:

• Lower immunity due to COVID isolation
• Removal of COVID precautions (e.g., masking, social distancing).
• People returning to their pre-pandemic activities
• Increased flu cases mixed with rising COVID cases (a “twindemic”)
• Low vaccine uptake (a recent survey found that only 49% of Americans plan to get a flu shot this year)

In a recent press release, William Schaffner, MD, the medical director for the National Foundation for Infectious Diseases (NFID), said that based on what experts have seen in the Southern Hemisphere, the flu has the potential to hit us hard this year.

“[But] on a positive note, we have more preventive behaviors in our toolbox than we did before the COVID-19 pandemic,” Schaffner added. “We are more accustomed to wearing masks and staying home when sick.”

How to Stay Healthy This Flu Season

In any flu season, but especially ahead of a bad one, getting a flu shot is one of the first and most important steps that you can take to protect yourself and the people around you.

In partnership with the NFID, the CDC recently rolled out its 2022-2023 Flu Vaccination Campaign in which it stressed the importance of getting a flu vaccine to help slow the spread and severity of the illness.

The campaign also announced three specific flu vaccines that are preferentially recommended for people aged 65 and older. These vaccines have been shown to be more effective for high-risk populations:

• Fluzone High-Dose Quadrivalent vaccine
• Flublok Quadrivalent recombinant flu vaccine
• Fluad Quadrivalent adjuvanted flu vaccine

In addition to getting vaccinated, the CDC also recommends taking other practical steps to prevent the flu such as:

• Avoiding close contact with sick people
• Staying home when you are sick
• Covering your mouth and nose when you cough or sneeze
• Washing your hands properly and often
• Avoiding touching your eyes, nose, and mouth
• Cleaning and disinfecting frequently touched surfaces in your home or workspace