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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-shots
  • 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.

What is different this year (2021-22) about flu season during COVID-19?

During the COVID-19 pandemic, it’s extra important for everyone to get their flu shot.  We need to prevent as much flu as we possibly can, so that our clinics and hospitals can focus on caring for patients who are ill with COVID-19 and other serious illnesses.

Frequent hand washing, wearing face masks, and social distancing also help to prevent both influenza and COVID-19. If you haven’t been vaccinated for COVID-19 or need a booster shot, you can get a flu and COVID-19 shot at the same time.

Also, during the 2021-22 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.

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 about 1 day before getting sick to 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.

How can I protect myself from the flu?

Use healthy habits:

  • 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.

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.  During the 2019-20 flu season the CDC estimated that flu caused 38 million illnesses, 400,000 hospitalizations, and 22,000 deaths in the United States.

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

Below is a list of groups of people who may get very sick if they have the flu.  It is important that they, and the people around them, get a flu shot.

  • People with lung disease like asthma
  • People of all ages with ongoing medical conditions like diabetes, heart disease, kidney or liver disease, blood cell disease including sickle cell, or neurological diseases that affect swallowing or breathing
  • Pregnant women and women who have given birth within 2 weeks
  • Children younger than 5 years, especially those younger than 2 years
  • Adults age 50 years and over
  • People with weak immune systems (due to disease or medicines)
  • Household contacts and caregivers of children younger than 5 years and adults aged 50 years and older, with particular emphasis on vaccinating contacts of children aged younger than 6 months; and
  • Household contacts and caregivers of people with medical conditions that put them at higher risk for severe complications from influenza.

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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(415) 554-2500

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