Kaiser Inpatient Data:
The Kaiser healthcare system provides medical care throughout the state to over one sixth of California residents. Thus, it is reasonable to
assume that influenza activity among Kaiser patients reflects the influenza activity for the entire state. Inpatient discharge diagnoses of
"pneumonia" and "influenza" (ICD-9 480-487) have been used to examine influenza trends in California; however, these data cannot be obtained
in real time. In contrast, inpatient admission diagnoses are
entered daily by text string and can be accessed the following day. For the purposes of this
project, the admission diagnoses of flu, pneumonia, and influenza
("flu admits") serve as surrogate markers for the more
accurate discharge diagnoses. Influenza activity is tracked by
dividing the number of flu admits by the total number of hospital admissions for the same day, thereby obtaining a percentage of influenza
admissions. Admissions for pregnancy, labor and delivery, birth, and outpatient procedures are excluded from the denominator.
Kaiser Pharmacy Data:
The number of prescriptions for drugs active against influenza, such as amantadine, rimantadine, zanamivir and oseltamivir, also serve as indicators of
influenza activity. This component of the project assesses the number of
influenza antiviral prescriptions filled weekly by all Kaiser outpatient
pharmacies in California.
Sentinel Physicians:
Sentinel providers (physicians, nurse practitioners, and
physician assistants) situated throughout California report the number of outpatient visits for influenza-like illness and the total number of
visits per week. This data is reported weekly as a percentage of total visits. California, through an intensive
recruitment campaign, has increased the sentinel provider enrollment
dramatically over the past few years, but has still not attained the
CDC goal of 1 sentinel provider per 250,000 population.
Virus Isolation Data and Characterization:
This component of the project involves use of data from hospital, academic, private and public health laboratories located throughout
California. These laboratories report the number of laboratory-confirmed influenza and other respiratory virus
detections and isolations on a weekly basis. A fraction of the influenza viruses isolated at
participating laboratories are forwarded to
VRDL for further antigenic and genetic characterization. Complete antigenic characterization enables detection of new strain variants and
provides a method for monitoring how well circulating influenza strains match those used in the current influenza vaccines. In addition,
sentinel physicians located throughout California submit specimens from patients with influenza-like illnesses for respiratory virus isolation at
VRDL.
Seventy-six influenza-confirmed
specimens were tested for antiviral resistance. 76% (26/34) of
influenza A/H3 specimens and 2% (1/41) of influenza A/H1
specimens had the S31N mutation consistent with adamantane
resistance. One specimen with a mixed influenza A/H1 and H3
infection also had adamantane resistance. No mutations
consistent with resistance to the neuraminidase inhibitors were
found.
Links for more facts about influenza:
Links for California
Influenza Surveillance data from 1999-2006:
