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Respiratory Viruses

Respiratory Viruses H​ub

Respiratory viruses are very active in the fall and winter. The viruses that can sometimes cause more serious illness are influenza (flu), respiratory syncytial virus (RSV) and SARS-CoV-2 (which causes COVID-19). These viruses spread quickly. When infected, most people will have a mild illness. But some people become seriously ill and can die. Learn more about the spread in your community and steps you can take to protect yourself.​

Key Highlights

  • ​Seasonal influenza activity is rising, particularly in the Bay Area and Southern California. Hospitalizations are currently low but are expected to increase. CDPH continues to recommend influenza vaccination, testing, and timely treatment.
  • A new H3N2 flu strain (subclade K) is causing severe early flu seasons in the Northern Hemisphere. Current influenza vaccines continue to offer protection, especially against severe disease.
  • RSV activity is increasing in California, especially among children. Hospitalizations are currently low but are expected to increase. Immunizations are recommended for all eligible persons.
  • COVID-19 activity remains very low statewide, with minimal test positivity, emergency room visits, and hospitalizations. CDPH continues to recommend COVID-19 vaccination, especially for those at increased risk and for all who choose protection.
  • Vaccines are available in California. Talk with your doctor or visit MyTurn to schedule your vaccine appointment today. ​
​Updated 11/21​/25

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Respiratory Virus Basics

Flu
RSV
COVID-19
Even healthy people can become very sick from a respiratory virus. Respiratory viruses like flu, RSV, and COVID-19 usually cause mild illnesses. They can cause severe complications in some people. Anyone at higher risk for serious illness should get medical help as soon as they start feeling sick. ​
  • Symptoms: Respiratory viruses affect your lungs and airways, making it hard to breathe. They can cause symptoms like coughing, body aches, and fever. 
  • Prevention: There are vaccines available for the flu, RSV, and COVID-19. Stay up to date for the best protection.  
  • Protection: To stay healthy, be sure to wash your hands a lot. Wear a mask in crowded spaces. Stay home and rest if you are sick.    
  • Treatment: Get tested quickly if you have symptoms. Start treatment early to prevent serious illness.

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