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Flu (Influenza): Facts for the Public

Where can I find information on flu vaccination?

  • https://www.sfcdcp.org/flushots
  • https://sf.gov/flu-vaccines
  • https://www.cdc.gov/flu/prevent/index.html

When is flu season?

We usually start seeing cases of influenza in November and continuing through late April.  The timing is a little different every year, sometimes a little earlier, sometimes a little later.  Peak influenza season is what we call it when we’re having a lot of cases at the same time, and that usually happens between December and March every year.  CDC has a page with a map of the flu season in the United States. 

After a few mild seasons, we could see more flu this year as people gather indoors, often without wearing masks. 

How can I protect myself from the flu? 

  • Get vaccinated every year, ideally during September or October, before the flu season starts. Annual flu vaccination is the best way to prevent flu in our community. 
  • Clean hands often with soap and water or use alcohol-based hand rub 
  • Don’t share personal items like toothbrushes or drinks 
  • Cover your mouth and nose with a tissue (or shirt sleeve) when sneezing, coughing, or nose blowing 
  • Clean frequently touched items and surfaces with soap and water 
  • Follow local rules about wearing a mask and social distancing. 
  • Your healthcare provider may prescribe an anti-viral medication that helps prevent or treat flu, if you are at risk of getting severe complications 

What is different about flu season during COVID-19?

With both flu and COVID circulating this season, it’s extra important for everyone to get their flu shot and any recommended COVID shots.  We need to prevent as much flu and COVID as we possibly can, to reduce the burden on our healthcare system and keep hospital beds open for those who need them. 

Frequent hand washing, wearing face masks, and social distancing also help to prevent both flu and COVID-19.  

Also, during the 2022-23 flu season, anyone who gets flu symptoms should:

  • Follow guidelines for home isolation
  • Get a COVID-19 test

That’s because of the similarity between flu symptoms and COVID-19 symptoms.  Fever, chills, cough, shortness of breath, headache, body aches, sore throat, extreme fatigue, and diarrhea could be flu or could be COVID-19.  Check with your healthcare provider or visit https://sf.gov/find-out-about-your-covid-19-testing-options.

I’m a senior, which flu shot should I get? 

If you are age 65 or older, CDC recommends that you get one of three flu vaccine products:  

  • Fluzone Hi-dose 
  • Flublok 
  • Fluad 

These “senior” flu vaccines provide the best protection against illness, hospitalization, and death. Ask your provider or pharmacy if they offer any senior flu vaccines. If none of these vaccines are available to you, any standard flu shot is okay and it’s much better to get a standard flu shot than none at all 

Learn more about senior flu vaccines here: Flu & People 65 Years and Older 

What is the flu?

The flu is a common infectious disease caused by influenza (flu) viruses. The flu usually affects a person’s breathing system. Seasonal flu generally occurs in the fall and winter and is caused by human influenza viruses.

How does the flu spread?

The flu spreads through tiny wet drops produced when a person coughs, sneezes, or talks. A person can get the flu by breathing in these wet drops, or by touching items and surfaces covered with these drops and then touching their mouth, nose, or eyes.

When can someone spread the flu to others?

People who have the flu may spread it to others from about 1 day before getting sick, until 5 -7 days after. Children and people with weak immune systems can spread the flu virus for a longer period of time. However, people are most contagious during the first three days of illness. 

What are signs and symptoms of the flu?

The usual signs and symptoms of the flu are cough, sore throat, runny or stuffy nose, body aches, headache, chills, and feeling very tired. Most people also have a fever. Others may vomit and have diarrhea.

How serious is the flu?

Most people get a mild case of flu that makes them sick for 1-2 weeks, then they get completely better.  Flu can also cause very severe disease, especially in babies, elderly people, and people with certain health conditions. Usually, influenza viruses cause tens of thousands of deaths and hundreds of thousands of people to be hospitalized nationwide, out of tens of millions of people who get the flu every year. You can find CDC estimates about how many people in the United States have been sick, hospitalized, or died from flu during the 2022–23 season here.

Who is more likely to get very sick with the flu?

Who is at higher risk for severe illness or hospitalization if they catch the flu: 

  • Babies and young children (<5 years) 
  • Pregnant people 
  • Older adults (≥65 years) 
  • Anyone with chronic medical conditions such as heart or lung disease, diabetes, HIV, a weakened immune system, etc. 
  • People who experience difficulties accessing healthcare such as BIPOC communities 
  • Residents of nursing homes or other long-term care facilities 

For people at high risk for severe illness or hospitalization, it is especially important to get a flu shot: an annual flu vaccination is the best protection against influenza. 

If you have flu-like symptoms, getting tested is also very important if you are at risk for severe illness. That is because there are specific pills that you can take for flu, and different pills that you can take for COVID, to prevent you from being hospitalized or dying.  The symptoms of COVID and flu are similar, so testing is the only way to tell them apart and get the right treatment. 

What should I do if I am sick with a flu-like illness?

During the COVID-19 epidemic, anyone who gets flu symptoms should:

  • Follow guidelines for home isolation
  • Get a COVID-19 test

That’s because of the similarity between flu symptoms and COVID-19 symptoms.  Fever, chills, cough, shortness of breath, headache, body aches, sore throat, extreme fatigue, and diarrhea could be flu or could be COVID-19.  Check with your healthcare provider or visit https://sf.gov/find-out-about-your-covid-19-testing-options.

Additional information

  • Flu Information for health care providers
  • Centers for Disease Control and Prevention (CDC) – Flu Page
  • California Department of Public Health (CDPH) – Flu Page

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