The specific illnesses circulating in your area depend on where you live and the time of year, but several infections follow predictable national patterns that likely affect your community right now. The three respiratory viruses the CDC tracks most closely are influenza, COVID-19, and RSV (respiratory syncytial virus), and all three circulate with overlapping seasonal peaks. Gastrointestinal bugs like norovirus also surge in winter months. The good news: free tools exist to check viral activity in your specific city or county, and we’ll walk you through them below.
The Big Three Respiratory Viruses
The CDC’s Respiratory Virus Hospitalization Surveillance Network monitors hospital admissions tied to influenza, COVID-19, and RSV across the country. These three viruses account for the vast majority of respiratory illness each year, and they tend to peak between late fall and early spring. COVID-19 is the least predictable of the three, with surges that can pop up in summer months as well.
RSV hits hardest in young children and older adults, typically peaking in December or January. Influenza follows a similar winter pattern but can linger well into March or April. COVID-19 waves have been more erratic, though winter remains a high-activity period.
Norovirus Peaks in Winter
If a stomach bug is tearing through your household, school, or workplace, norovirus is the most likely culprit. CDC outbreak data from the NoroSTAT network shows norovirus activity climbs sharply in late fall and peaks in winter, with the highest outbreak counts typically hitting in December. During the 2025-2026 tracking season, the week of December 5th saw 56 reported outbreaks, one of the highest single-week totals.
Norovirus spreads incredibly easily through contaminated food, surfaces, and close contact. Symptoms include sudden vomiting, diarrhea, and stomach cramps, usually lasting one to three days. It’s miserable but rarely dangerous for otherwise healthy adults. Young children, older adults, and people with weakened immune systems face higher risks of dehydration.
Walking Pneumonia in Kids
Mycoplasma pneumoniae, the bacterium behind most cases of “walking pneumonia,” surged in 2024 and remains elevated in some parts of the country. The spike was unusual because it hit very young children hard. Infections in the 2-to-4-year-old and 5-to-17-year-old age groups peaked in August 2024, and even infants saw increased rates, which historically has been uncommon.
Since early 2025, overall Mycoplasma infections have been declining, but regional pockets of activity persist. As of late January 2026, about 3.1% of pneumonia-related emergency department visits among children ages 5 to 17 involved a Mycoplasma diagnosis, compared to just 0.6% across all age groups. If your child has a lingering cough, low-grade fever, and mild fatigue but seems well enough to go about their day, walking pneumonia is worth considering.
How to Tell These Illnesses Apart
COVID-19, the flu, and RSV share a frustrating number of symptoms: fever, cough, sore throat, body aches, fatigue, and congestion. A few clues can help you narrow it down.
- Speed of onset: Flu symptoms appear fast, typically one to four days after exposure. COVID-19 takes longer, anywhere from two to 14 days.
- Loss of taste or smell: This remains more characteristic of COVID-19 than the flu, though it’s become less common with newer variants.
- Duration of contagiousness: People with COVID-19 can spread the virus for a longer window than those with seasonal flu.
- Stomach symptoms: Vomiting and nausea can occur with both flu and COVID-19 but are more common in children. If vomiting and diarrhea are the primary symptoms with little respiratory involvement, norovirus is more likely.
- Wheezing in young children: RSV often causes bronchiolitis in babies and toddlers, leading to wheezing and difficulty breathing that looks different from a standard cold.
Home COVID tests remain the quickest way to rule one virus in or out. The federal government has offered free test kits through COVIDTests.gov, shipped for free via USPS, with up to four kits per household.
How to Check What’s Spreading in Your Area
You can’t Google your way to hyperlocal illness data, but several public tools get remarkably close.
Wastewater surveillance is the fastest signal available. When people are infected, viral fragments show up in sewage before most patients even get tested. Many counties now publish wastewater dashboards that track COVID-19, flu, and RSV concentrations by sewershed, the geographic zone feeding a specific treatment plant. Santa Clara County in California, for example, monitors four treatment facilities covering 98% of the population and publishes data broken down by city. Search your county’s public health department website for “wastewater” or “respiratory virus dashboard” to find your local version. Stanford University’s WastewaterSCAN project powers many of these trackers.
The CDC’s RESP-NET dashboard lets you view hospitalization rates by surveillance site, age group, and virus type. It won’t pinpoint your zip code, but it shows regional trends that reflect what’s circulating near you.
The Walgreens Respiratory Index tracks flu and COVID-19 activity using prescription fills, testing results, and over-the-counter cold and flu product purchases from Walgreens stores nationwide. You can search by state or local market to see how your area ranks. It updates weekly.
How Well Current Vaccines Protect You
Vaccines for all three major respiratory viruses are available, and while none offers complete protection, the numbers on hospitalization prevention are meaningful. A review published in the New England Journal of Medicine found that updated COVID-19 vaccines reduced hospitalization risk by about 50% in adults and 37% in people with weakened immune systems. Flu vaccines cut hospitalization risk by 48% in adults ages 18 to 64 and by 67% in children.
These numbers mean vaccines won’t necessarily stop you from catching something, but they substantially lower the odds of ending up seriously ill. That’s especially relevant during peak respiratory season when multiple viruses circulate simultaneously and hospitals see the highest demand.