The Norovirus Tracker

This season against the last two

The CDC says norovirus outbreaks are most common from November to April. In wastewater, the 2024-25 season was the bigger of the last two, peaking in the week ending January 4, 2025. Last season peaked later, in the week ending February 21, 2026, at about 38% of that height.

Outbreaks reported to the CDC

The CDC’s NoroSTAT network counts norovirus outbreaks reported by 12 states. They reported 27 outbreaks for August 1–September 4, 2026, against 29 in the same period last season. In the CDC’s words, this season is so far “within the middle 50% of outbreaks (interquartile range) reported in the same period during the 2012–2026 seasonal years.”

Peaks as the CDC published them at the end of each season. The number of reporting states changes between seasons, so compare shapes rather than exact totals.

Which strain is going around

There are many kinds of norovirus, which is why the CDC says you can catch it many times in your life. Public-health labs in the CDC’s CaliciNet network type the virus behind confirmed outbreaks. The CDC notes that in years when there is a new strain of the virus, there can be 50% more norovirus illness.

Source: CDC CaliciNet, page updated September 3, 2026. CaliciNet shows which strains are circulating more reliably than how much illness there is.

Cruise ships

The CDC’s Vessel Sanitation Program has posted 9 gastrointestinal outbreaks on cruise ships in 2026 so far, 5 of them norovirus. By the same date last year it had posted 19; all of last year came to 23, 18 of them norovirus. The CDC posts an outbreak only when at least 3% of passengers or crew report gastrointestinal illness on a voyage it oversees, so the count moves with how many people sail as well as with the virus. The CDC says norovirus causes over 90% of diarrheal outbreaks on cruise ships, but cruise outbreaks are only a small percentage (1%) of all norovirus outbreaks.

Source: CDC Vessel Sanitation Program outbreak list, last updated July 23, 2026. Each ship links to the CDC’s notice.

Recalls and shellfish warnings

When norovirus shows up in a recall, it is almost always shellfish, usually raw or frozen oysters. The CDC advises cooking oysters and other shellfish thoroughly, to an internal temperature of at least 145°F. Recent federal actions:

Sources: FDA alerts and advisories list; FDA enforcement reports via openFDA (data through September 23, 2026). Recalls are regulatory actions, not a measure of risk. Our Gut Health Recall Tracker covers every gut-pathogen recall since 2019.

The bug itself, in the CDC’s words

• What it is. “Norovirus is a very contagious virus that causes vomiting and diarrhea. It is sometimes called the ‘stomach flu’ or the ‘stomach bug.’ However, norovirus illness is not related to the flu.” CDC
• How fast and how long. “A person usually develops symptoms 12 to 48 hours after being exposed to norovirus.” And: “Most people with norovirus illness get better within 1 to 3 days.” CDC
• How long it spreads. “You are most contagious when you have symptoms of norovirus illness or during the few days after you feel better.” But “studies have shown that you can still spread norovirus for 2 weeks or more after you feel better.” CDC
• Soap beats sanitizer. “Hand sanitizer does not work well against norovirus.” Soap and water “work to remove all types of germs from hands, while sanitizer acts by killing certain germs on the skin.” CDC
• Cleaning up. The CDC’s recipe for a disinfecting bleach solution is 5 to 25 tablespoons of household bleach (5% to 8%) per gallon of water, left on the surface for at least 5 minutes, or an EPA-registered disinfectant that works against norovirus. CDC
• How common. The CDC estimates norovirus causes 19 to 21 million illnesses in the United States each year, and about 2,500 reported outbreaks. Outbreaks “occur throughout the year but are most common from November to April.” CDC
• Where outbreaks happen. “Over half of all norovirus outbreaks reported in the United States occur in long-term care facilities.” CDC

If you are caring for someone who is sick, or you are unsure about dehydration, a clinician or pharmacist is the right person to ask.

Questions people ask

Is there a stomach bug going around right now?

As of October 1, 2026, WastewaterSCAN rated norovirus in US wastewater LOW nationally. For the week ending September 26 the national level was 19% lower than the same week last year. CDC NoroSTAT states reported 27 outbreaks for August 1–September 4, 2026, against 29 in the same period last season. Norovirus outbreaks are most common from November to April, according to CDC.

When is norovirus season?

CDC says norovirus outbreaks occur throughout the year but are most common from November to April. In wastewater, the 2024-25 season peaked in the week ending January 4, 2025, and the smaller 2025-26 season in the week ending February 21, 2026, according to WastewaterSCAN data.

How long does norovirus last?

According to CDC, a person usually develops symptoms 12 to 48 hours after being exposed to norovirus, and most people get better within 1 to 3 days. The main symptoms are vomiting and diarrhea. This is educational information, not medical advice.

How long is norovirus contagious?

CDC says people are most contagious when they have symptoms and during the few days after they feel better, but studies have shown norovirus can still spread for 2 weeks or more after someone feels better. CDC advises people who are sick not to prepare or handle food or care for others until at least 2 days (48 hours) after symptoms stop, especially if they work in a restaurant, school, daycare or long-term care facility.

Does hand sanitizer kill norovirus?

Not well. CDC says hand sanitizer does not work well against norovirus and is not a substitute for handwashing, which is best. CDC explains that soap and water work to remove all types of germs from hands, while sanitizer acts by killing certain germs on the skin, and it names norovirus among the germs soap and water remove more effectively.

What strain of norovirus is going around?

In CDC CaliciNet data for September 1, 2025 – August 31, 2026, GII.4 Sydney[P16] caused 73 of 153 genotyped outbreaks (47.7%), the largest share. The season before, GII.17[P17] caused most outbreaks. CDC notes that in years when there is a new strain of the virus, there can be 50% more norovirus illness.

How we build this page

Every Monday we pull the latest public numbers, check several of them against what each agency’s own page shows, and update this page. We do not forecast, and we do not estimate cases. Wastewater levels show how much virus is moving through sewersheds, not how many people are sick; NoroSTAT counts outbreaks, not individual illness, in the states that take part; the cruise list only includes voyages the CDC oversees.

• NoroSTAT weekly outbreaks by season (CSV)
• Every CDC-listed cruise-ship GI outbreak since 1994 (CSV)
• FDA norovirus recalls since 2012 (CSV)
• Full method, sources and checks

Wastewater readings: WastewaterSCAN (data.wastewaterscan.org), shown here as WastewaterSCAN’s own ratings and our week-on-week and year-on-year comparisons; their data are licensed CC BY-NC 4.0 and are not included in our downloads. These data were collected as part of the WastewaterSCAN / SCAN project, a partnership between Stanford University, Emory University, and Verily funded philanthropically through a gift to Stanford University. Data citation: A. B. Boehm et al., Pathogen nucleic acids data in wastewater solids from 147 treatment plants in the United States: 2024-2025, Data in Brief, 2026.

Outbreaks, strains and cruise ships: CDC NoroSTAT, CDC CaliciNet and the CDC Vessel Sanitation Program. Recalls: FDA. Our CSVs are free to reuse under CC BY 4.0 with a link to this page.