H1N1 Flu Data and Statistics
Weekly California H1N1 Flu Summary Data
Reported Hospitalizations, ICU and Fatal Cases of 2009 H1N1 Influenza Infections in California (as of January 30, 2010)
Weekly Number of Hospitalized/Fatal 2009 H1N1 Influenza Cases in California by Week of Report, Week Ending April 28 - January 30, 2010
H1N1 Flu Graphs
For more information, see:
CDPH Enhanced Surveillance for H1N1 (2009) Influenza Virus (PDF) 
- Week ending January 30, 2010
Monthly Provisional H1N1 Flu Data Tables by Local Health Jurisdiction
Provisional Data Tables - Reported hospitalizations, ICU cases, and deaths by local health jurisdiction, plus historical data tables (updated monthly, last updated February 4, 2010) 
Provisional Maps - Historical maps of reported cases by local health jurisdiction (maps discontinued as of July 16, 2009)
Information About Data Posting on This Website
Starting September 27, H1N1 Flu Provisional Data Tables will be posted to this website on a monthly basis (for example, data for November will be posted during the first week of December). The summary statewide H1N1 Flu data (table on this page) will continue to be udpated weekly on Thursdays.
All data is considered provisional and is subject to change. Local Health Jurisdictions include the 58 California county health departments and 3 city health departments (Berkeley, Long Beach, and Pasadena). The city health department jurisdiction data are not included in the county jurisdiction totals.
Changes in H1N1 Flu Data Reporting
As the current H1N1 Flu unfolds, CDPH continues to perform surveillance and provide PCR testing for influenza, confirmatory testing for H1N1 Flu 2009, and guidance and assistance to our local public health partners. Effective July 15, 2009, local health departments were no longer asked to report outpatient cases. Effective August 12, 2009, local health departments were asked to report hospitalized cases of H1N1 Flu as weekly aggregate numbers. Intensive care unit cases and fatal cases will continue to be reported with individual case report forms. Effective September 8, 2009, CDPH changed the timeframe for reporting H1N1 Flu cases. In response to requests from local health jurisdictions (LHJs), CDPH now uses a reporting week consistent with the MMWR week, namely Sunday through Saturday, rather than the Tuesday to Tuesday reporting week previously in place. LHJs will continue to report their weekly data to CDPH every Tuesday by 12:00 pm.
The reporting changes are based on the following:
Need to focus efforts on documenting and understanding the most severe cases of disease to target our treatment and prevention efforts.
Hospitalizations and fatalities provide the most accurate measure of disease severity in California communities and serve the public health goal of tracking H1N1 Flu disease trends; and
H1N1 Flu is now widespread throughout California and reporting outpatient cases does not assist in further efforts to understand the pandemic.
The Centers for Disease Control and Prevention has also changed their reporting of data.
The reported number of cases of H1N1 Flu in California do not reflect how many actual cases there may be in the state because individuals in outpatient settings are no longer being tested for the presence of the virus and many cases go undetected due to the mild nature of disease among most people. Laboratory testing is limited to individuals with serious H1N1 Flu illness, including hospitalized patients, and those at high risk for complications. An update of the number of cases is published on a weekly basis to provide an estimate of H1N1 Flu frequency among those patients being tested.
Additional Information About H1N1 Flu Surveillance and Reporting