The California Sentinel Provider Influenza-like Illness Surveillance Program is a partnership between clinicians, local health departments (LHDs), the California Department of Public Health (CDPH), and the Centers for Disease Control and Prevention (CDC) to conduct surveillance for influenza-like illness (ILI). The program has been contributing valuable information to state, national, and global influenza surveillance efforts since 1988.

Information collected by California sentinel providers is used in combination with clinical and laboratory data, vaccination status, antiviral usage, and severe case data throughout the state to monitor the timing, location, and impact of influenza and other respiratory viruses year-round.

How it Works

Sentinel Providers report the number of patients seen with ILI in five age categories (0–4 years, 5–24 years, 25–49 years, 50–64 years, >64 years) and the total number of patients seen for any reason. Reports are submitted on a weekly basis to the CDC.

Case definition for Influenza-like Illness

• Any illness with fever (≥100°F or 37.8°C) − temperature can be from measurement in the office or at home, AND
• Cough and/or sore throat 

Compiling and reporting data usually takes less than 15 minutes per week. Participating sentinel providers receive weekly updates on state and national influenza activity.

Virologic Testing 

Nasal, throat, or nasopharyngeal swabs from selected patients are submitted to the CDPH Viral and Rickettsial Disease Laboratory (VRDL) for viral testing free of charge. Specimen collection kits are replenished as specimens are submitted. 

It is especially important to collect and submit specimens early in the season (October-December), when influenza isolates are forwarded to the CDC to identify which strains are circulating and should be considered as candidate strains for the next season’s influenza vaccine. The goal for each sentinel provider is to submit three ILI specimens per week to the VRDL. This target helps to meet the CDPH sampling goal of testing specimens from patients of various age groups throughout the state during the entire influenza season. The laboratory results provide situational awareness of circulating influenza and SARS-Cov-2 viruses and populations affected. Additionally, laboratory testing of specimens from sentinel providers allows us to conduct surveillance for drug resistance and emergence of novel influenza virus strains that may lead to an influenza pandemic.

ILI specimens submitted to VRDL will be tested for influenza A, B, and SARS-CoV-2 using the CDC’s Influenza SARS-CoV-2 Multiplex Assay. Specimens that test positive by PCR for influenza type A will then be further subtyped while specimens testing positive for influenza type B will be genotyped for lineage.

Specimens should be collected from patients with influenza-like illness (oral temperature of 100^oF [or 37.8^oC], AND cough and/or sore throat), especially those with any of the following:

• Severe disease
• Recent overseas travel
• Recent swine exposure
• Occurring in an outbreak setting
• Who have received this season’s influenza vaccine

We are particularly interested in specimens from patients with ILI who present:

• At the beginning of the influenza season
• During the peak of the influenza season
• At the end of the influenza season

Interested in Becoming a Sentinel Provider?

By reporting weekly ILI data and sending respiratory specimens to the VRDL for laboratory testing, sentinel providers play a critical role in state and national influenza and other respiratory virus surveillance. Your participation enables us to monitor the impact of influenza and other respiratory viruses and helps to guide prevention and control policies, vaccine strain selection, and recommendations for patient care.

Providers of any specialty (e.g., family practice, internal medicine, pediatrics, infectious diseases) in any type of practice (e.g., private practice, public health clinic, urgent care center, emergency room, university student health center) are eligible to be sentinel providers. In addition, sentinel providers may be physicians, nurse practitioners or physician assistants.​

Enrollment Information

Submit the Sentinel Provider Enrollment Form​ (PDF) via Fax: 510-620-3949 or Email: InfluenzaSurveillance@cdph.ca.gov

If you are having difficulty accessing documents on this page please call 510-620-3737 or email ImmunizationBranch@cdph.ca.gov to request information in an alternate format. ​​