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Influenza (Flu) and Other Respiratory Diseases

Influenza or flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness and at times can lead to death. The best way to prevent influenza is by getting a flu vaccination each year. 

The Centers for Disease Control and Prevention (CDC) recommends a yearly flu vaccine for everyone 6 months of age and older as the first and most important step in protecting against this serious disease. While there are many different flu viruses, the flu vaccine is designed to protect against the flu strains that research indicates will cause the most illness during the flu season. Traditional flu vaccines (called trivalent vaccines) are made to protect against three flu viruses: an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. There are also flu vaccines available that protect against four flu viruses (called "quadrivalent" vaccines). These vaccines protect against the same viruses as the trivalent vaccines as well as an additional B virus.

Getting the flu vaccine as soon as it becomes available each year is best. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against the flu. Influenza seasons are unpredictable and can begin as early as October.

  • To find flu vaccine near you, visit: http://flushot.healthmap.org/. Check in advance about cost and insurance coverage; influenza vaccine is typically covered by health insurance.
  • Many local health departments and other clinics offer free or low-cost influenza vaccines.
  • The California Vaccines for Children program provides no-cost vaccines to eligible children 18 years old and younger. Clinics participating in the California Vaccines for Children program may be located at http://eziz.org/vfc/provider-locations.

Californians can also take some basic steps to protect themselves and their families from getting flu and other respiratory infections. Make sure to wash your hands often, cover coughs and sneezes with your sleeve or a tissue, and stay home when you are sick.

View personal stories of people affected by flu at ShotbyShot.org. For more information about flu, visit www.flu.gov.

The California Department of Public Health (CDPH) Influenza Surveillance Program is a collaborative effort between CDPH, the CDC, Kaiser Permanente, California local health jurisdictions and participating sentinel providers and laboratories. Annual influenza epidemics follow a winter seasonal pattern in the United States with typical activity peaking during late December to early February. CDPH obtains and analyzes clinical, pharmacy and laboratory data year-round in an effort to determine the timing and impact of influenza activity and to determine how well circulating strains of the virus match those used in the current influenza vaccines.

The most current weekly report on influenza and other respiratory disease activity can be found below, under "Hot Topics & Updates."

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Last modified on: 7/20/2017 3:29 PM