Influenza Update

From Wisconsin Division of Public Health (March 2026):

• The DHS recommends that clinicians continue administering RSV monoclonal antibody products to eligible infants until April 30, 2026.

Influenza is at a low level and declining in Wisconsin. Rates of influenza-like illnesses (ILI) in Wisconsin outpatients are very low.

CDC estimates that there have been at least 31 million illnesses, 380,000 hospitalizations, and 23,000 deaths from flu so far this season. Across the U.S. there were 1,938 (4.7%) influenza detections at clinical laboratories, from the 41,363 specimens collected last week. Of detected influenza viruses at public health laboratories last week, 45.0% were influenza A and 55.0% were influenza B. Among influenza A viruses, 65.3% were H3, 34.7% were H1, and 0% were H5. CDC has reported current match estimates between circulating and vaccine strains for this season (H3: 2%; H1: 99%; B: 34%).

The percentage of primary care patients with influenza-like illness (ILI) is 1.9% and is at a low level. ILI activity is low in 3 states, and minimal in 47 states; Wisconsin has minimal levels. Six additional pediatric deaths have been reported. 109 pediatric deaths due to influenza A and 40 due to influenza B have been reported for the 2025-2026 season to date; with one death in Wisconsin. Among children who were eligible for influenza vaccination and with known vaccination status, approximately 85% of reported pediatric deaths this season have occurred in children who were not fully vaccinated against influenza.

5.4% of all deaths during week 14 (Apr. 5-11) were due to pneumonia, influenza, or COVID-19, and below the seasonal epidemic threshold.

Rapid influenza and COVID-19 testing is problematic at present due to low levels of viruses. Positive results need confirmation. Negative tests can be trusted.

• Only 33.8% of Wisconsinites have received influenza vaccine this season.
• See: https://www.dhs.wisconsin.gov/immunization/influenza.htm

• Only 13.2% of Wisconsinites have received the updated 2025/2026 COVID-19 vaccine.
  • See: https://www.dhs.wisconsin.gov/immunization/covid-19-vaccine-data.htm

https://www.cdc.gov/flu/hcp/antivirals/summary-clinicians.html

Antiviral treatment is recommended as soon as possible for any patient with suspected or confirmed influenza who:

• is hospitalized
• has severe, complicated, or progressive illness
• is at higher risk for influenza complications.

Decisions about starting antivirals for patients with suspected influenza should not wait for laboratory confirmation. Empiric antiviral treatment should be started as soon as possible in the above priority groups. Clinicians can consider early empiric antiviral treatment of non-higher-risk outpatients with suspected influenza based upon clinical judgment if treatment can be initiated within 48 hours of illness onset.

Antiviral Drug Options - supplies may be limited

• For hospitalized patients with suspected or confirmed influenza, initiation of antiviral treatment with oral or enterically administered oseltamivir is recommended as soon as possible.
• For outpatients with complications or progressive disease and suspected or confirmed influenza (e.g., pneumonia, or exacerbation of underlying chronic medical conditions), initiation of antiviral treatment with oral oseltamivir is recommended as soon as possible.
• For outpatients with suspected or confirmed uncomplicated influenza, oral oseltamivir, inhaled zanamivir, intravenous peramivir, or oral baloxavir may be used for treatment, depending upon approved age groups and contraindications.

The most common viral causes of acute respiratory infections in Wisconsin primary care practices are rhinovirus/enterovirus, influenza B and RSV. For the week ending April 18, 2026, 1.4% of 7,238 specimens tested across Wisconsin and compiled by the Wisconsin State Laboratory of Hygiene were positive for SARS-CoV-2. The most commonly identified gastopathogens are norovirus and rotavirus.

Over the past 4 weeks the typical ARI case has been 46.2 years old; 67% 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 4.8 days after illness onset. 33% of illnesses are characterized as mild, with 67% having moderate symptoms and 0% having severe symptoms.

*estimate based on WSLH statewide data

** estimate based on primary care patients seen at five clinics and 1 urgent care in Dane County

*** includes HKU1, NL63, 229E and OC43