Flu season in the United States
Current flu, COVID-19, and RSV activity in the United States — based on the CDC's NHSN weekly hospital admission rates and FluView surveillance. Hospitalization signals translated into a qualitative low / moderate / high assessment.
Current situation: Influenza
In week 15 of 2026, activity of influenza (seasonal flu) in the United States is low. The trend — derived from weekly hospital admission rates — is falling. Over a four-week comparison, a clear decline is visible.
The classification is based on the CDC's NHSN weekly hospitalization data and the FluView surveillance report. Seasonally, infection waves in the United States typically peak between December and February; activity is usually markedly lower during the summer months. How severe a given season becomes depends on the circulating virus variant and the population's immune status, among other factors.
Data sources and methodology
The current picture for the United States is built on the CDC's National Healthcare Safety Network (NHSN) weekly hospital admissions data. NHSN collects laboratory-confirmed admission rates per 100,000 population for influenza, COVID-19 and RSV, submitted by participating hospitals nationwide. We rescale these hospitalization rates into a consultation-equivalent signal so the qualitative “low / moderate / high” categories are consistent with how we report other countries.
CDC NHSN (Hospital Respiratory Data)
NHSN is the CDC's national surveillance system for healthcare-associated infections. Since 2022, hospitals report weekly counts of confirmed influenza, COVID-19 and RSV admissions. We use the jurisdiction-level USA rates (admissions per 100,000 population per week), which give an unbiased picture of severe illness pressure on the healthcare system.
CDC FluView
CDC FluView is the long-running weekly flu surveillance report, drawing on outpatient ILI visits via the ILINet sentinel network, public health laboratory results, and hospitalization data. While our headline level is driven by NHSN, FluView provides the context for how a season compares to the typical seasonal curve.
Why hospitalization rates
Unlike clinic visits or self-reports, hospital admissions remain reliable across changes in testing behaviour and reporting practices. They reflect severe outcomes — the load that matters most for health-system capacity — and are reported with a roughly one-week lag.
Qualitative classification
The “low”, “moderate” and “high” categories follow seasonal reference values and epidemiological thresholds calibrated to match our classifications for other countries. Hospitalization rates are scaled to consultation-equivalent incidence using pathogen-specific conversion factors derived from typical seasonal peaks in both systems. Data refreshes weekly when the CDC publishes the latest NHSN update, typically late in the week.
Frequently asked questions
When is flu season in the United States?
Flu season in the US typically runs from October through May. Activity usually begins climbing in late October or November, peaks between December and February, and tails off through April. The exact timing and intensity vary considerably year to year and region to region, influenced by the circulating influenza subtypes and population immunity carried over from previous seasons.
How bad is the current flu season?
The overall picture is tracked by the CDC through its weekly FluView report and NHSN hospital admissions data. The CDC classifies seasonal activity on a scale from minimal to very high, based on indicators like outpatient visits for influenza-like illness (ILI), laboratory-confirmed cases, and hospitalization rates. A season is considered severe when hospital admission rates climb past the thresholds observed in past severe years.
What's the difference between the flu and a cold?
The flu (influenza) typically comes on abruptly with high fever, body aches, a dry cough, and significant fatigue. A cold develops more gradually and is usually milder, with symptoms like a runny nose, sore throat, and mild cough — rarely with fever in adults. The flu is more likely to cause serious complications, especially in older adults, young children, and people with chronic conditions.
Should I get a flu shot?
The CDC recommends an annual flu vaccine for everyone aged 6 months and older, with rare exceptions. The shot is especially important for people at higher risk of complications: adults over 65, pregnant women, young children, and those with chronic conditions like asthma, heart disease, or diabetes. The vaccine takes about two weeks to become fully effective, so getting vaccinated early in the season offers the best protection.
How do I protect myself from the flu?
Vaccination is the most effective single measure. Beyond that, frequent handwashing, avoiding close contact with visibly ill people, covering coughs and sneezes, and staying home when sick all reduce community transmission. Indoor ventilation and, in high-risk settings, well-fitted masks provide additional protection during peak season.
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