2024 - 2025 Weekly Influenza Update: 09/29/2024 -
10/26/2024 (Week 40 -
43)
Fresno County Department
of Public Health
The 2024 - 2025 influenza season began on 09/29/2024 (week 40). This
surveillance report monitors influenza activity and is updated weekly
through the end of the 2024 - 2025 season. Providers must report
laboratory-confirmed influenza-associated fatal pediatric cases in those
0-17 years old.1 Fresno County Public Health obtains the
number of influenza-associated fatal cases between 0 and 17 years of age
from investigations. The number of influenza-associated deaths in those
18 years and older are obtained from vital statistics records. National
death and viral surveillance data is from the CDC’s FluView2
applications. California death data is from the California Respiratory
Virus Weekly Report.3
INFLUENZA ASSOCIATED DEATHS LOCAL, STATE AND
NATIONAL
Table 1: Cumulative Influenza Associated Deaths
for the 2024 - 2025 Influenza Season by Location and Age
Range
| Fresno County4 09/29/2024-10/26/2024 |
0 |
0 |
0 |
0 |
| California3 06/30/2024-10/26/2024 |
1 |
9 |
29 |
39 |
| Nationwide2 09/29/2024-10/19/2024 |
0 |
10 |
45 |
55 |
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 10/19/2024
(week 42). 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 10/19/2024 (week 42). 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 10/19/2024 (week
42). 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 10/19/2024 (week 42). 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
10/26/2024 (week 43). 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.
INFLUENZA A CONCENTRATIONS IN
WASTEWATER
Figure 6 shows the concentration of influenza A in wastewater samples
from Fresno County as of 10/12/2024 (week 41).7 The blue dots
represent the average concentration of influenza A for all wastewater
samples collected on that date. The black line is the 10-day rolling
average of influenza A concentrations and helps to view data trends.
Samples are collected from the Fresno-Clovis Regional Wastewater
Treatment Facility. More information detailing wastewater surveillance
can be found
here.