What is Influenza (Flu)?

Influenza, commonly known as “the flu,” is an infectious respiratory illness caused by influenza viruses. There are two main types of influenza viruses that cause illness in people: influenza A and influenza B.

How do you get influenza?

Influenza viruses are most commonly spread via droplets when people cough, sneeze or talk. These droplets can land in the mouths or noses of people who are nearby. A person might also get influenza by touching a surface or object that has influenza virus on it and then touching their own mouth or nose.

What are the symptoms of influenza?

Influenza symptoms may include fever, chills, cough, sore throat, body aches, fatigue, and runny or stuffy nose. Most people who get influenza will recover in several days to less than two weeks, but some people will develop severe illness that requires hospitalization. Many viruses other than influenza A and B can also cause influenza-like symptoms.

What can I do to protect myself?

Vaccination is the best method in preventing influenza each year. More information about influenza vaccinations can be found here:  Information on getting a flu shot.

People who are sick should stay home and avoid close contact with others. Good health habits such as washing your hands often, covering your mouth and nose with a tissue when coughing or sneezing, and avoiding touching your eyes, mouth, or nose can prevent you and/or others from becoming ill.

Seasonal Influenza Surveillance

Each influenza season, Orange County Health Care Agency partners with local hospitals, primary care providers, and universities to conduct influenza surveillance. Annual influenza epidemics follow a winter seasonal pattern in the United States with typical activity peaking during late December to February. Surveillance activities help to monitor and prepare for the impact of influenza on the healthcare system. Moreover, influenza surveillance in California is vitally important to monitor for importation of novel strains of influenza from other parts of the world.
Surveillance for influenza activity in Orange County includes monitoring of the following components year-round:

  • Influenza viruses: specimens are submitted to Public Health Laboratory from participating hospitals, physicians, and laboratories for tracking and strain-typing.
  • Influenza-like illnesses (or ILI): sentinel providers (physicians, nurse practitioners, physician assistants) report outpatient influenza-like illnesses and submit specimens.
  • Pneumonia and influenza deaths: death certificates are reviewed for deaths from pneumonia or influenza.
  • Severe influenza and deaths: reported by health care providers and hospital infection control professionals.
  • Outbreaks of respiratory illness: investigation is conducted and control measures are recommended to prevent further disease transmission.
  • Enhanced surveillance for human cases of avian influenza: health care providers are requested to report any patients with fever and respiratory symptoms who traveled to affected areas in the 7-10 days prior to symptom onset (specific criteria will be distributed as novel strains are identified).

Current Influenza Activity

For Physicians and Health Care Providers

We are actively recruiting physicians and other health care providers to participate as sentinel providers for influenza surveillance.
For more information about becoming a sentinel provider, or if you wish to receive our Eye on Influenza newsletter, please contact us


Page Last Updated:  September 26, 2018