Welcome to the 2024-2025 influenza season. Over the next several months, I will try to provide weekly updates on influenza’s passage across Wisconsin, along with updates on SARS-CoV-2, enhanced by excellent surveillance data made available by the Wisconsin Division of Public Health, the Wisconsin State Laboratory of Hygiene, the Centers for Disease Control and Prevention, and the World Health Organization. I will make predictions based on trend data and my experience in reading the seasonal patterns of influenza. I will also provide clinical guidance. Should you have any questions, please do not hesitate to contact me.
Influenza is at low levels in Wisconsin.
Across the U.S. there were 359 (0.8%) influenza detections at clinical laboratories, from the 46,025 specimens collected last week. Of detected influenza viruses at public health laboratories last week, 100% were influenza A and 0% were influenza B. Among influenza A viruses, 51.7% were H3 and 48.3% were H1. CDC has reported current match estimates between circulating and vaccine strains (H3: 79%; H1: 98%; B: 100%) for this season. The percentage of primary care patients with influenza-like illness (ILI) is at 2.1% and is well below baseline. ILI activity is minimal in all states; Wisconsin has minimal levels. No pediatric deaths have been reported for the 2024-2025 season to date.
Wisconsin has recorded 17 hospitalizations for influenza this season. This is lower than 2023-2024 (20) at this point.
The performance of rapid influenza testing is reduced because of low levels of circulating virus.
The performance of rapid SARS-CoV-2 testing is reduced because of declining levels of circulating virus.
Only 16.1% of Wisconsinites have received influenza vaccine this season.
Only 7.9% of Wisconsinites have received the COVID-19 vaccine this season.
Viruses associated with acute respiratory infections in Wisconsin primary care practices have been dominated by Rhinovirus. For the week ending 10/05/2024, 8.8% of 8,008 specimens tested across Wisconsin by the Wisconsin State Laboratory of Hygiene and clinical labs were positive for SARS-CoV-2. The most commonly identified gastopathogens are norovirus and Campylobacter.
Over the past 4 weeks the typical ARI case has been 39.3 years old. 60% of patients have been female. 20% of patients identified a sick contact 1-3 days before illness onset and they typically present to the clinic 9.6 days after illness onset. 20% of illnesses are characterized as mild, with 80% having moderate symptoms and 9% having severe symptoms.
| Viruses in Circulation | Percent* in statewide laboratory surveillance | Percent** in primary care surveillance clinics |
|---|---|---|
| Influenza A | 23.4 | 0 |
| Influenza B | 9.6 | 14 |
| Seasonal Coronavirus*** | 1.6 | 14 |
| RSV | 5.3 | 0 |
| Parainfluenza | 7.7 | 29 |
| hMPV | 7.1 | 14 |
| Rhino/Enterovirus | 18.8 | 29 |
| Adenovirus | 1.6 | 0 |
| Bocavirus | 0 | 0 |
| SARS-CoV | 24.8 | 0 |
The 7-day average for patients hospitalized for COVID-19 in Wisconsin is 132 (declining).
Across Wisconsin, 1,036,702 individuals (17.6% of the population) have received the updated 2023/2024 COVID-19 vaccine.
Across Wisconsin, 466,091 individuals (7.9% of the population) have received the updated 2024/2025 COVID-19 vaccine.
Please refer to guidance provided by Wisconsin Department of Health Services and by the U.S. Centers for Disease Control and Prevention.
* The weekly influenza update is adapted from an email from Jon Temte, MD, PhD; Chair, Wisconsin Council on Immunization Practices; Professor, Department of Family Medicine and Community Health, University of Wisconsin School of Medicine and Public Health.
