Influenza is at low levels in Wisconsin.
Across the U.S. there were 1,426 (3.1%) influenza detections at clinical laboratories, from the 46,425 specimens collected last week. Of detected influenza viruses at public health laboratories last week, 70.6% were influenza A and 29.4% were influenza B. Among influenza A viruses, 53.7% were H3 and 46.3% were H1. CDC has reported an excellent match between circulating and vaccine strains (H3: 98%; H1: 100%; B: 100%) for this season. As of 5/10/2024, CDC estimates that there have been at least 34 million illnesses, 380,000 hospitalizations, and 24,000 deaths from flu. The percentage of primary care patients with influenza-like illness (ILI) declined to 2.1% and is well below baseline. ILI activity is low to minimal in all states; Wisconsin has minimal levels. 164 pediatric deaths, due to influenza A (87), influenza B (74), and influenza A/B coinfection (3), have been reported for the 2023-2024 season to date.
Wisconsin has recorded 3,853 hospitalizations for influenza this season. This is lower than in 2019/2020 (3,998) and higher than 2022/2023 (3,555) at this point.
The performance of rapid influenza testing is reduced because of low levels of circulating virus.
RIDT(+) results may need to be confirmed using RT-PCR. RIDT(-) results can be trusted
The performance of rapid SARS-CoV-2 testing is reduced because of declining levels of circulating virus.
RSDT(+) results may need to be confirmed using RT-PCR. RSDT(-) results can be trusted
Only 35.2% of Wisconsinites have received influenza vaccine this season.
Viral causes of acute respiratory infections in Wisconsin primary care practices continued to be mixed with an abundance ofRhinovirus. For the week ending 5/4/2024, 3.2% of 7,119 specimens tested across Wisconsin by the Wisconsin State Laboratory of Hygiene and clinical labs were positive for SARS-CoV-2. About 1.0% of primary care patients are presenting with acute diarrheal illness. The most commonly identified gastopathogens are norovirus and rotavirus.
Over the past 4 weeks the typical ARI case has been 16.8 years old. 67% of patients have been female. 0% of patients identified a sick contact 1-3 days before illness onset and they typically present to the clinic 4.0 days after illness onset. 60% of illnesses are characterized as mild, with 40% 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 72 (declining), with a 7-day average of 10 (13.9%) requiring intensive care.
Across Wisconsin, 1,036,702 individuals (17.6% of the population) have received the updated 2023/2024 COVID-19 vaccine.
5.9% of all deaths during week 18 (Apr. 28 - May 4) were due to pneumonia, influenza, or COVID-19, and below the seasonal epidemic threshold.
Forecasting by the CDC indicates a low and stable level of COVID-19 hospitalization over the next four weeks.
Variants: the national proportions of variants for the week ending April 27, 2024, include: KP.2 (28.2%) JN.1 (15.7%), JN.1.7 (13.3%); JN.1.1.6 (10.0), JN.1.13.1 (8.8%), and KP.1.1 (7.1%). SARS-CoV-2 continues to be a rapidly diversifying virus.
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.
