Flu Season 2026–2027: CDC Update, Flu Shot Strains and Who Needs One

The 2026–2027 flu season has started in the United States, and it has started a little early. In its FluView report for the week ending October 10, 2026, published on October 16, the Centers for Disease Control and Prevention (CDC) said influenza activity is still low nationally but has been rising since late August and early September, with the highest levels on the West Coast. A flu shot in 2026 is still the main protection, and CDC says most people should get one during September or October.

Below: what the CDC, the World Health Organization (WHO) and the UK Health Security Agency (UKHSA) report so far, this year's vaccine strains, who should get vaccinated and when, lessons from Australia, a symptom comparison, antivirals and an H5N1 update.

Flu season 2026: what the latest CDC data shows

The CDC counts each flu season by surveillance weeks. The 2026–2027 season officially began on October 4, 2026, and runs until October 2, 2027. Only two weeks in, lab positivity, doctor visits, emergency visits and hospitalizations for flu are all rising.

A few details stand out in the CDC report:

• H1N1 is leading so far. Of 300 flu viruses reported by public health labs in the latest week, 292 were influenza A and 8 were influenza B. Among the influenza A viruses that were subtyped, 96.4% were A(H1N1)pdm09 and 3.6% were A(H3N2). Since late May, about four in five influenza A viruses have been H1N1, most of them from a group the CDC calls the D.3.1.1 subclade.
• Early, but not abnormal. The CDC said early-season activity is higher than it usually is at this point of the year but still within the normal range of variation between seasons.
• Children are showing up first. In national emergency department data, flu accounted for 0.8% of visits across all ages in the latest week, but 1.8% among children under 5 and 2.0% among those aged 5 to 17.
• No pediatric deaths yet this season. The CDC said no flu-associated child deaths occurring in the 2026–2027 season had been reported as of its latest update. For context, the CDC counted 288 pediatric flu deaths in the 2024–2025 season, according to Reuters.

What WHO and UKHSA are seeing outside the US

In England, UKHSA's weekly surveillance report from October 15 put flu positivity at 6.0% for the week to October 11, roughly stable after a jump the week before. Influenza A positivity was highest among people aged 18 to 24. Between late August and October 11, UKHSA's lab genetically characterised 177 seasonal flu viruses: 111 were H1N1, 59 were H3N2 and 7 were influenza B. So the UK, like the US, is seeing more H1N1 than H3N2 in the opening weeks.

Last winter is the reason health agencies are watching closely. UKHSA notes that in the 2025–2026 season a drifted H3N2 variant known as subclade K began circulating around five weeks earlier than usual, from mid-October. The vaccines still worked against it, especially in children, and UKHSA modelling suggests flu vaccination prevented around 100,000 hospitalisations and about 7,000 deaths in England that season. When WHO met in February 2026 to pick strains for this winter, subclade K accounted for most influenza viruses reported across regions.

WHO estimates that seasonal flu causes around a billion infections worldwide each year, including 3 to 5 million cases of severe illness and an estimated 290,000 to 650,000 respiratory deaths.

Lessons from Australia's 2026 flu season

Countries in the Northern Hemisphere often look to the Southern Hemisphere's winter for clues, although it is not a reliable forecast. Australia's season in 2026 was later than last year's and more typical in size. According to the Australian Respiratory Surveillance Report covering September 21 to October 4, 2026:

• Australia recorded 195,297 notified flu cases from January 1 to October 4, 2026, far fewer than in 2025's record year.
• Activity rose in a sustained way only from late July and peaked around late August to early September, a pattern similar to pre-pandemic seasons such as 2015–2018.
• Among 1,428 viruses characterised by sentinel labs this year, 71.9% were H3N2, 18.8% H1N1 and 9.2% B/Victoria, the reverse of the H1N1-led start now seen in the US and UK.
• More than 87% of the viruses tested were a good match for the 2026 Southern Hemisphere vaccine.
• Preliminary estimates suggest vaccination cut the risk of a GP visit with flu by 58% and the risk of hospitalization with flu by 35%, with higher protection against hospitalization in adults aged 65 and older (49%).
• Only about 30.5% of Australians had been vaccinated by early October.

The lesson: a flu shot does not stop every infection, but it lowers the chance of severe illness, and low uptake leaves more people exposed. The strain mix can also differ by hemisphere, which is why the Northern Hemisphere vaccine is chosen separately.

The 2026–2027 flu vaccine: which strains it covers

WHO announced its Northern Hemisphere recommendation on February 27, 2026, and the US Food and Drug Administration's vaccine advisory committee (VRBPAC) met on March 12, 2026, and voted for the same trivalent composition for US vaccines. All US flu vaccines this season protect against three viruses: one influenza A(H1N1), one influenza A(H3N2) and one influenza B/Victoria. All three components changed from last season.

Component	Egg-based vaccines	Cell-based, recombinant or mRNA vaccines
Influenza A(H1N1)pdm09	A/Missouri/11/2025-like virus	A/Missouri/11/2025-like virus
Influenza A(H3N2)	A/Darwin/1454/2025-like virus	A/Darwin/1415/2025-like virus
Influenza B (Victoria lineage)	B/Tokyo/EIS13-175/2025-like virus	B/Pennsylvania/14/2025-like virus

The names refer to reference viruses and where and when each was isolated. Egg-based and cell-based vaccines use slightly different reference viruses for H3N2 and B because viruses can change as they grow in eggs.

There is one new type of vaccine this year. On August 5, 2026, the FDA approved Moderna's mFLUSIVA, the first mRNA-based flu vaccine, for adults aged 50 and older. It joins the existing options in the US: standard-dose shots made in eggs or cells, the high-dose and adjuvanted shots for people 65 and older, the recombinant Flublok shot, and the FluMist nasal spray, which is approved for ages 2 through 49 and can be ordered for home use through the FluMist Home program.

Who should get a flu shot in 2026, and when

CDC's interim clinical guidance for the 2026–2027 season, updated September 1, 2026, keeps routine annual flu vaccination for everyone aged 6 months and older. The agency says that, because of legal uncertainties, the flu recommendations in its July 2025 immunization schedule remain in effect this season.

Why the US guidance was in question this year

On January 5, 2026, the CDC, under Acting Director Jim O'Neill, dropped its long-standing universal recommendation that all children get a flu shot and moved it to shared clinical decision-making with a health care provider, Reuters reported. Federal officials said insurance would still cover the shots. On March 16, 2026, US District Judge Brian Murphy in Boston ruled that this change was unlawful because the CDC had acted without its Advisory Committee on Immunization Practices (ACIP), and he also found the reconstituted committee itself was improperly formed. HHS said it expected the ruling to be overturned on appeal. Several medical groups, including the American Academy of Pediatrics and the American Academy of Family Physicians, published their own 2026–2027 recommendations, and they also back annual flu vaccination.

Timing

• Most people: one dose, ideally in September or October. If you have missed that window, CDC says vaccination should continue as long as flu viruses are circulating.
• Children 6 months to 8 years who need two doses (usually those getting a flu vaccine for the first time): the first dose as soon as possible, and the second at least four weeks later, ideally by the end of October.
• Adults 65 and older: CDC preferentially recommends a high-dose, recombinant or adjuvanted vaccine. If none is available, any age-appropriate flu vaccine is better than none.
• Pregnancy: flu vaccination is recommended during pregnancy and helps protect the baby in the first months of life. CDC advises against vaccination in July and August for most adults and for women in the first or second trimester, so that protection lasts through the season.
• Egg allergy: people with egg allergy can receive any flu vaccine appropriate for their age and health, with no extra precautions beyond those for any vaccine.

In England, the adult flu programme started on October 1, 2026, with most vaccinations to be completed by the end of November. NHS eligibility covers people aged 65 and over, people with certain health conditions, pregnant women, young children and school-age children, carers and frontline health and social care workers. In Canada and Australia, provincial and state health departments run their own programmes, so check the rules where you live.

You can get a flu shot and an updated COVID-19 vaccine at the same visit. In the US, most insurers and Medicare Part B cover the flu shot with no out-of-pocket cost.

Flu vs COVID vs RSV vs norovirus: how the symptoms compare

Several viruses circulate at once in late autumn and winter, and their symptoms overlap. Flu usually hits suddenly, with fever, body aches and exhaustion. COVID-19 can look very similar. RSV often starts like a cold but can be serious in babies and older adults. Norovirus, often called the "stomach flu", is not influenza at all; it is a gut infection that causes vomiting and diarrhea. If you mainly have stomach symptoms, our guide to norovirus symptoms and when to worry is a better fit than this article.

Feature	Flu (influenza)	COVID-19	RSV	Norovirus
Onset	Sudden	Gradual or sudden	Gradual, cold-like	Sudden
Time from exposure to symptoms	About 1–4 days	About 2–14 days	About 4–6 days	About 12–48 hours
Fever	Common, often high	Common	Sometimes, usually mild	Sometimes, low-grade
Cough	Common, dry	Common	Common, can become wheezy	Rare
Body aches and fatigue	Very common, can be severe	Common	Mild	Common
Runny or stuffy nose	Sometimes	Common	Very common	No
Loss of taste or smell	Uncommon	Possible	Uncommon	No
Vomiting and diarrhea	Sometimes, more in children	Sometimes	Uncommon	Main symptoms
Typical length	Several days to under 2 weeks	Varies widely	1–2 weeks	1–3 days
Prescription treatment	Antivirals (oseltamivir, baloxavir and others)	Antivirals for higher-risk people	Supportive care	Fluids and rest

Because the overlap is large, a test is the only reliable way to know which virus you have. Many pharmacies sell combined home tests for flu and COVID-19. Norovirus spreads differently, mostly through contaminated hands, surfaces and food, and it stays contagious for days after you feel better; see how long norovirus is contagious and norovirus vs food poisoning for how to tell it apart from other stomach bugs. Our norovirus outbreak tracker follows CDC data on that virus through the winter.

Flu antivirals: oseltamivir, baloxavir and when to use them

Prescription antivirals can shorten flu illness and lower the risk of complications. CDC recommends starting treatment as soon as possible, ideally within 48 hours of the first symptoms, for anyone with suspected or confirmed flu who is hospitalized, has severe or worsening illness, or is at higher risk of complications. Doctors can also prescribe them to otherwise healthy people who are seen early.

• Oseltamivir (Tamiflu and generics): a pill or liquid taken twice a day for five days. It can be used at any age, including newborns, and is the usual choice in pregnancy and for hospitalized patients.
• Baloxavir (Xofluza): a single oral dose, approved for people aged 5 and older for treatment and also to prevent flu after close contact with an infected person. CDC does not recommend it during pregnancy or breastfeeding because there is not enough safety data.
• Zanamivir (Relenza): an inhaled medicine for ages 7 and up, not suitable for people with asthma or other airway disease.
• Peramivir (Rapivab): a single intravenous dose, for ages 6 months and older.

CDC monitors flu viruses for resistance. In the latest report, eight H1N1 viruses carried changes that reduced how well oseltamivir inhibited them, but most circulating viruses remain susceptible to the recommended antivirals. Older drugs called adamantanes (amantadine and rimantadine) are no longer recommended because resistance to them is widespread.

Higher-risk groups include adults 65 and older, children under 5, pregnant women, nursing home residents and people with chronic conditions such as asthma, heart disease, diabetes or a weakened immune system.

When to seek medical care for flu

Most people recover from flu at home with rest, fluids and fever reducers such as acetaminophen or ibuprofen. Get urgent care for difficulty breathing, chest pain or pressure, confusion, severe weakness, seizures, not urinating, a fever above 104°F (40°C), or symptoms that improve and then return worse, which can signal pneumonia. In children, also watch for fast breathing, bluish lips and dehydration. Stay home until you have been fever-free for at least 24 hours without medicine, and cover coughs to protect others. General healthy habits such as sleep and a balanced diet help; supplements such as vitamin D3 and K2 are no substitute for vaccination.

H5N1 bird flu: where things stand

H5N1 bird flu continues to circulate in wild birds and some animals, but the CDC rates the current risk to the general public as low and reports no known person-to-person spread. Since February 2024, 72 human cases of A(H5) bird flu have been reported in the United States, most linked to dairy cattle or poultry farm work, and one death occurred in Louisiana. As of October 14, 2026, no new human infections with a novel flu virus had been reported for the new season. Worldwide, the CDC counts 1,022 human H5N1 cases reported since 1997 as of June 2026, mostly after close contact with sick or dead poultry. Seasonal flu shots do not protect against H5N1.

What to watch for the rest of the 2026–2027 flu season

In the US, flu activity usually climbs through November and December and peaks between December and February, though some seasons peak as late as March. The main questions are whether H1N1 keeps its lead or H3N2 takes over later, and how well the vaccine matches. The CDC publishes FluView every Friday, and UKHSA publishes its surveillance report every Thursday. Early vaccine effectiveness estimates usually appear in winter. For anyone who has not had a flu shot yet, the advice from health agencies in all three countries is the same: now is a good time.