Current Weekly Influenza Update

INFLUENZA ASSOCIATED DEATHS LOCAL, STATE AND NATIONAL

Table 1: Cumulative Influenza Associated Deaths for the 2024 - 2025 Influenza Season by Location and Age Range

INFLUENZA TYPING AT NATIONAL, REGIONAL, STATE AND LOCAL LEVELS

Figure 1 shows the cumulative distribution of influenza types from national, CDC Region 9 and California from 09/29/2024 to 03/15/2025 (week 11). CDC Region 9 includes California, Arizona, Hawaii and Nevada.²

Figure 2 shows the weekly distribution of influenza types in CDC Region 9 from 09/29/2024 to 03/15/2025 (week 11). CDC Region 9 includes California, Arizona, Hawaii and Nevada.²

Figure 3 shows the number of influenza positive tests by disease week and influenza type in Fresno County from 09/29/2024 to 03/15/2025 (week 11). The number of weekly tests changes throughout the season (figure 4). The data for figure 3 comes from both public health and clinical laboratories.⁵

Figure 4 shows the number of weekly influenza tests, and the percentage of those test that are positive for influenza in Fresno County from 09/29/2024 to 03/15/2025 (week 11). The data for figure 4 comes from both public health and clinical laboratories.⁵

INFLUENZA-LIKE-ILLNESS (ILI) AT EMERGENCY DEPARMENTS

Figure 5 shows the percent of ED visits attributed to influenza-like illness (ILI) in previous seasons and the current season as of 03/29/2025 (week 13). The baseline and alert curves provide reference points to monitor ILI activity in the current season. The baseline curve and alert thresholds are estimated using prior seasons’ data from 2018 to 2023. The baseline curve is the average expected percent of ED visits due to ILI. The alert curve is the upper 95% confidence limit based off percent ED visits due to ILI. Because COVID-19 and influenza have similar symptoms, ILI from the 2019-2020 season onward may be skewed. Data on previous seasons and current seasons is collected through EpiCenter,⁶ a syndromic surveillance system.