The 2025-2026 winter season in the USA is coming to an end. The subclade K of Influenza A (H3N2) became the predominant strain, with the highest severity in the pediatric (0-17 y/o) population, resulting in 25 million cases, 330,000 hospitalizations, and 20,000 deaths. COVID-19 peaked in late summer with a 9.2% positivity rate and is currently below 3% nationwide, with low levels. RSV had a lower level of activity this year with onset later than usual, and hospitalizations have remained elevated through April. Respiratory virus panels have expanded revealing more hospital cases of Human Metapneumovirus (hMPV), Parainfluenza virus. and Rhinovirus.
Outbreaks of Influenza in NHs (nursing homes) are common and a major threat to our residents. An outbreak is defined as two or more cases in the same unit within 72 hours. Public Health should be notified immediately. The IDSA and CDC advise starting antiviral treatment right away for residents who are symptomatic, without waiting for laboratory confirmation. Molecular assays (like RT-PCR) are more sensitive than rapid antigen tests. All non-ill residents on the unit should be offered chemoprophylaxis with oseltamivir, if not contraindicated. This should continue for at least 14 days or until at least 7 days after the last known case. Unvaccinated staff should be offered chemoprophylaxis. Facilities should follow standard droplet and source control precautions.
Until this year, the value of chemoprophylaxis in NHs, though supported by observational trials, has lacked high-quality randomized controlled trials (RCTs). On March 30, 2026, Silva et al published in JAMA Internal Medicine a sequential target trial and randomized censor-weight approach to emulate a cluster-randomized trial of oseltamivir chemoprophylaxis in NHs. They analyzed 400 outbreaks in 318 NHs and found a 21% relative risk reduction in 14-day hospitalization risk in NHs where at least 70% of eligible residents had received oseltamivir within 2 days of the outbreak. The comparator group was facilities where 0-70% residents had received treatment within 2 days. The editors noted these impressive results may reflect other factors, such as better staffing, more staff infection prevention training, and well-resourced infection prevention teams. They recommend that facilities make timely and effective decisions during influenza outbreaks.
Immunization rates in SNFs for the 2025-2026 season for NH Residents:
- Influenza is estimated at 70-75% in the USA (78-82% in California)
- COVID-19 is 38-44% in the USA (45-52% in California)
For SNF Employees in the USA:
- Influenza is 76% if on-site vaccinations are used, but < 50% if not
- COVID-19 is 40-45% - highest for Physicians and RNs, and lowest for non-clinical staff
Immunization rates for employees are higher if strongly recommended by the employer and on-site vaccinations.