San Diego County’s latest Respiratory Virus Surveillance Report shows influenza continuing at elevated levels, with emergency department visits coded for influenza running above the county’s prior-year average.

In CDC Week 4, 4.3% of emergency department visits resulted in an influenza diagnosis, compared with a 3.7% prior-year average for the same week, according to the county’s syndromic surveillance indicators.  

The report, dated Feb. 5, 2026, with data through Jan. 31, 2026, lists 1,937 influenza cases in Week 4, slightly higher than 1,906 in Week 3. The season-to-date total stands at 11,429 influenza cases.  

Influenza-related hospitalizations remained substantial. San Diego County reported 208 influenza hospitalizations in Week 4 and 1,236 hospitalizations season-to-date; the county notes figures are preliminary and may change due to delayed reporting and additional information obtained during investigations.  

For context, the same Week 4 reporting table shows 102 COVID-19 cases and 204 RSV cases, while 0.2% of emergency department visits resulted in a COVID-19 diagnosis and 0.2% resulted in an RSV diagnosis.  

The county defines the respiratory virus “season” as CDC disease weeks 27–26 and notes it starts 2025–26, reporting on June 29, 2025.  

Subtype surveillance indicates that Influenza A has been the dominant driver of flu detections locally. In the report’s season-to-date subtype breakdown, Influenza A accounts for 85.8%, compared with 10.5% for Influenza B, with smaller shares for Influenza A H1N1pdm09 (1.0%) and Influenza A H3 (2.7%), plus trace “type unknown.”