Flu and COVID-19 cannot be told apart by their symptoms alone, according to the Centers for Disease Control and Prevention, which says testing is needed to confirm a diagnosis. The agency says the two share many of their symptoms. The differences it describes are that a change in or loss of taste or smell is more frequent with COVID-19, and that COVID-19 symptoms can take longer to appear after infection. This page reports what the CDC states and is not personal medical advice.

The symptoms the two illnesses share

The CDC's page on the similarities and differences between flu and COVID-19 says both are contagious respiratory illnesses caused by different viruses. Flu is caused by infection with an influenza virus, and COVID-19 is caused by infection with a coronavirus, SARS-CoV-2, the page says. It lists these as common symptoms that the two share:

• Fever or feeling feverish and having chills, with a note that not everyone with flu will have a fever
• Cough
• Shortness of breath or difficulty breathing
• Fatigue (tiredness)
• Sore throat
• Runny or stuffy nose
• Muscle pain or body aches
• Headache
• Vomiting
• Diarrhea
• Change in or loss of taste or smell

Where the CDC says they differ

The differences the CDC describes are in how often a symptom occurs and when symptoms start, and it does not name a symptom that only one of the two illnesses causes.

Every row comes from the CDC's flu and COVID-19 comparison page. The same page says that a person with COVID-19 could take longer from the time of infection to experience symptoms than a person with flu.

The CDC's separate symptom pages describe the start of each illness. Its page on the signs and symptoms of flu says flu symptoms usually come on suddenly. Its page on the symptoms of COVID-19 says symptoms may appear 2 to 14 days after exposure to the virus, and that they may start as mild, with some people progressing to more severe symptoms.

How each symptom list reads

The CDC keeps one symptom page for each illness, and the lists are worded slightly differently.

The left column comes from the CDC's flu symptoms page, which says vomiting and diarrhea are more common in children than adults, and the right column comes from its COVID-19 symptoms page. For more on the flu list, see What are the symptoms of the flu?

Testing and having both at once

The CDC's comparison page says testing can also show whether someone has both flu and COVID-19 at the same time, which it describes as uncommon. The page says people with both at the same time can have more severe illness than people with either one alone.

How long each one spreads

The CDC says a person with COVID-19 could be contagious for a longer time than a person with flu.

The page says young children and people with weakened immune systems may be contagious with flu for longer periods of time. For how long flu illness lasts, see How long does the flu last?

Emergency warning signs the CDC lists for COVID-19

The CDC's COVID-19 symptoms page lists these as emergency warning signs for COVID-19:

• Trouble breathing
• Persistent pain or pressure in the chest
• New confusion
• Inability to wake or stay awake
• Lips, nail beds and skin that may appear pale, gray or blue, depending on skin tone

The CDC's emergency warning signs for flu in children and adults are listed on What are the symptoms of the flu?

For how much flu and other respiratory illness is circulating now, see Is flu and respiratory illness high in my state? For the months when flu spreads most, see When is flu season?

Flu is in general worse than the common cold, with symptoms that are typically more intense and begin more abruptly, while cold symptoms are usually milder, according to the Centers for Disease Control and Prevention. The agency says the two illnesses have similar symptoms, so it can be difficult to tell the difference between them based on symptoms alone. This page reports what the CDC states and is not personal medical advice.

How the CDC compares the symptoms

The CDC's page on the signs and symptoms of flu carries this comparison of a cold and flu:

The agency's Cold Versus Flu page says people with colds are more likely to have a runny or stuffy nose than people who have flu. For the full list of flu symptoms and the emergency warning signs the CDC names, see What are the symptoms of the flu?

Different viruses cause them

The CDC says flu and the common cold are both contagious respiratory illnesses, but they are caused by different viruses. Flu is caused by influenza viruses only. The common cold can be caused by a number of different viruses, including rhinoviruses, parainfluenza and seasonal coronaviruses.

The agency's About Common Cold page says more than 200 respiratory viruses can cause colds, and that rhinoviruses are the most frequent cause of colds in the United States. The same page says the viruses that cause COVID-19, flu and RSV can also cause cold-like symptoms but do not cause colds, and that those viruses are more likely to cause severe illness.

What the CDC says about a cold

The CDC's About Common Cold page says colds usually last less than a week. It says the signs and symptoms of a cold usually peak within 2 to 3 days of infection and can include:

• Runny nose
• Nasal congestion
• Cough
• Sneezing
• Sore throat
• Headache
• Mild body aches
• Fever, which the page says is usually low grade in older children and adults

The same page says adults in the United States have an average of two to three colds every year, and children often have more.

How serious each one can be

The CDC's Cold Versus Flu page says colds generally do not result in serious health problems, such as pneumonia, bacterial infections or hospitalizations. It says flu can have serious associated complications.

For how long flu illness runs, see How long does the flu last? For when flu circulates, see When is flu season?

How flu is diagnosed

The CDC says special tests can tell if a person is sick with flu. Its page on flu diagnosis says testing is the only way to know if a person has flu, though a health care provider may diagnose flu based on symptoms.

That page says a number of tests are available to detect influenza viruses in respiratory specimens. It says rapid influenza diagnostic tests can provide results within approximately 10 to 15 minutes but may not be as accurate as other flu tests.

The CDC's About Common Cold page tells people who have cold-like symptoms and suspect they have COVID-19 or flu to get tested. For how much flu is circulating now, see Is flu and respiratory illness high in my state?

The Centers for Disease Control and Prevention classifies the severity of the 2026-2027 flu season so far as low across all ages, according to its weekly report for the week ending Saturday, October 31, 2026. The same report says flu activity is higher than is typically observed this early in the season, and that an earlier rise does not necessarily lead to a higher peak or a more severe season overall.

The season so far in numbers

The agency estimates that the season has brought at least 1,700,000 illnesses, 25,000 hospitalizations and 1,400 deaths so far. The figures below come from the same report, which the agency published on Friday, November 6, 2026, and which covers Week 43 of the year.

The report says the hospital admission rate of 2.5 per 100,000 people rose from the week before. Clinical laboratories found flu in 4,696 of the 51,351 specimens they tested that week, which is 9.1%.

What the measures mean

The outpatient figure counts visits for influenza-like illness, which the agency defines as a fever of 100 degrees Fahrenheit or higher with a cough, a sore throat or both. Because that definition rests on symptoms and not on a test, it can include illnesses other than flu. The 2.8% reported for the week was below the national baseline of 2.9%.

The illness, hospitalization and death totals are estimates and not counts, and the agency states each one as "at least" a given number. The report also says, "All data are preliminary and may change as more reports are received."

Which virus is spreading

Influenza A(H1N1)pdm09 viruses were the ones public health laboratories reported most often, according to the report. Of the 388 influenza A viruses those laboratories subtyped in the week, 379, or 97.7%, were A(H1N1)pdm09.

Deaths of children

Three deaths of children from flu in the 2026-2027 season have been reported to the agency, according to the report. The report puts the total for the previous season, 2025-2026, at 202.

When the numbers change

The agency updates its national flu report once a week, on Fridays after 11 a.m. A flu season is counted from Week 40 of one year through Week 39 of the next. The newest report is linked from the agency's FluView page, and this page is updated at the same address after each release.

For the level of respiratory illness in one state, see Is flu and respiratory illness high in my state?

What this page is not

This page reports public health data and is not medical advice. National figures do not say whether any one person is ill or what that person should do, and questions about symptoms belong with a doctor or a local health department.

Most people who get flu recover in a few days to less than two weeks, according to the Centers for Disease Control and Prevention. The agency says some people develop complications, such as pneumonia, that can be life-threatening. This page reports what the CDC states and is not personal medical advice.

The flu timeline

The first and third rows come from the CDC's page on how flu spreads. The second and fourth rows come from its page on the signs and symptoms of flu, where the fever figure appears in a table that compares a cold with flu. That page also says flu symptoms usually come on suddenly and that not everyone with flu will have a fever.

What the symptoms are

The CDC says people who have flu often feel some or all of these signs and symptoms:

• Fever or feeling feverish, or chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue (tiredness)
• Vomiting and diarrhea in some people, which the agency says is more common in children than in adults

For the symptoms of norovirus, see What are the symptoms of norovirus?

How long a person with flu is contagious

The CDC says influenza viruses can be detected in most infected people beginning one day before symptoms develop and up to five to seven days after becoming sick. People with flu are most contagious during the first three days of their illness, according to the same page. The agency says some people, including young children and people with weakened immune systems, may be contagious for longer.

When the CDC says a person can return to normal activities

The CDC's guidance on preventing the spread of respiratory viruses says a sick person should stay home and away from others, and can go back to normal activities when both of these have been true for at least 24 hours:

• Symptoms are getting better overall.
• The person has not had a fever and is not using fever-reducing medication.

The same page says to take added precautions over the next 5 days after returning, such as steps for cleaner air, good hygiene, a well-fitted mask, physical distancing or testing. The reason the agency gives is that a person at that point is typically less contagious, but the body still needs more time to fully get rid of the virus. The page says a person who develops a fever or starts to feel worse after returning should stay home and away from others again.

Whether treatment shortens the flu

The CDC's page on flu treatment says flu antiviral drugs can lessen symptoms and shorten the time a person is sick by about a day. The agency says the drugs work best when started early, ideally within two days after flu symptoms begin.

When flu lasts longer or gets worse

The CDC lists sinus and ear infections as examples of moderate complications from flu and pneumonia as a serious one. The agency says flu can also make chronic medical problems worse, and gives asthma attacks in people with asthma as an example.

The same page gives emergency warning signs and says people who have them should get medical care right away. For adults, the signs it lists are:

• Difficulty breathing or shortness of breath
• Persistent pain or pressure in the chest or abdomen
• Persistent dizziness, confusion or inability to arouse
• Seizures
• Not urinating
• Severe muscle pain
• Severe weakness or unsteadiness
• Fever or cough that improve but then return or worsen
• Worsening of chronic medical conditions

The CDC gives a separate list for children, which includes fast breathing or trouble breathing, bluish lips or face, and any fever in a child younger than 12 weeks. The agency says its lists do not include every sign and that a medical provider should be consulted about any other symptom that is severe or concerning.

To see how much respiratory illness the CDC is reporting where you live, see Is flu and respiratory illness high in my state?

The symptoms of flu are fever or feeling feverish and chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches and fatigue, according to the Centers for Disease Control and Prevention. The agency says the symptoms usually come on suddenly, and that a person may have some or all of them. This page reports what the CDC states and is not personal medical advice.

The symptoms the CDC lists

The CDC's page on the signs and symptoms of flu gives this list:

• Fever or feeling feverish and chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue (tiredness)
• Vomiting and diarrhea in some people, which the agency says is more common in children than adults

The same page says not everyone with flu will have a fever. The CDC's About Influenza page says some people infected with an influenza virus do not develop any symptoms at all.

When symptoms start and how long they last

The first and third rows come from the CDC's About Influenza page, and the second comes from its page on signs and symptoms. The About Influenza page also says some otherwise healthy adults may be able to infect others beginning one day before symptoms develop and five to seven days after becoming sick.

For how much flu is circulating now, see Is flu and respiratory illness high in my state?

Flu, a cold or something else

The CDC says flu and the common cold are both respiratory illnesses but are caused by different viruses. Its comparison of the two describes the onset of a cold as gradual and the onset of flu as abrupt.

The agency's About Influenza page says it can be very difficult to tell flu apart from other viral or bacterial respiratory illnesses based on symptoms alone, and that tests are available to diagnose flu. For the symptoms of norovirus, see What are the symptoms of norovirus?

Emergency warning signs

The CDC says people who have these warning signs should get medical care right away. It lists these signs in children:

• Fast breathing or trouble breathing
• Bluish lips or face
• Ribs pulling in with each breath
• Chest pain
• Severe muscle pain (child refuses to walk)
• Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
• Not alert or interacting when awake
• Seizures
• Fever above 104 degrees Fahrenheit that is not controlled by fever-reducing medicine
• In children younger than 12 weeks, any fever
• Fever or cough that improve but then return or worsen
• Worsening of chronic medical conditions

It lists these signs in adults:

• Difficulty breathing or shortness of breath
• Persistent pain or pressure in the chest or abdomen
• Persistent dizziness, confusion, inability to arouse
• Seizures
• Not urinating
• Severe muscle pain
• Severe weakness or unsteadiness
• Fever or cough that improve but then return or worsen
• Worsening of chronic medical conditions

The CDC says these lists are not all inclusive and that a person should consult a medical provider for any other symptom that is severe or concerning.

What the CDC says about treatment

The CDC's page on flu treatment says antiviral drugs for flu are prescription medicines, and that they work best when started within two days of symptoms beginning. The page says antibiotics do not work against viruses such as influenza.

The same page says people with flu symptoms who are at higher risk of complications, who are very sick or who are worried about their illness should contact a health care provider. The CDC's signs and symptoms page names people 65 and older, people with certain chronic conditions such as asthma, diabetes or heart disease, pregnant women and children younger than 5 among those at higher risk.

Flu season in the United States usually occurs in the fall and winter, and flu activity most often peaks between December and February, according to the Centers for Disease Control and Prevention. The agency says seasonal flu viruses are detected year-round in the United States, and that influenza viruses typically circulate during the fall and winter.

Which month flu peaks

The CDC charts the peak month of each flu season from 1982-1983 through 2023-2024. It defines the peak month as the month with the highest percentage of respiratory specimens testing positive for influenza virus infection. February was the peak month most often.

The CDC says there was no discernible peak in flu activity during the 2020-2021 season, because the level of influenza virus circulation that season was uncharacteristically low.

How the CDC tracks the season

The CDC publishes flu activity in a weekly surveillance report called FluView and in a tool called FluView Interactive. The agency says the data it collects are used to update both on the following Friday, and it describes a week-long delay between the collection of flu surveillance data and its reporting.

Flu is not the only virus that spreads at this time of year. The CDC's flu season page says other respiratory viruses circulate during flu season too, including the virus that causes COVID-19 and respiratory syncytial virus (RSV), which it describes as the most common cause of severe respiratory illness in young children. The level of respiratory illness that the CDC reports for each state this week is on the page Is flu and respiratory illness high in my state?

When the CDC says to get a flu vaccine

The CDC says that everyone 6 months and older in the United States, with rare exception, should get a flu vaccine every season. For most people who need only one dose for the season, it says September and October are generally good times to be vaccinated, and that, ideally, everyone should be vaccinated by the end of October.

The CDC says flu vaccines cause antibodies to develop in the body about two weeks after vaccination.

The key facts at the top give CDC's national count of confirmed measles cases this year, with last year's total and the share of cases hospitalized. The table lists the count for each state and jurisdiction CDC reports, highest first.

What the count includes

CDC says its counts include only confirmed cases that jurisdictions have notified to CDC, and that it is aware of probable cases that are not in these numbers. The table lists jurisdictions as CDC does, so New York City appears separately from New York. CDC says its counts for 2025 and 2026 are preliminary and subject to change.

Why a state's own count can differ

CDC says state health departments and CDC post measles counts on different schedules, so a state's website can show a different number, and that states have the most up-to-date information about cases and outbreaks in their jurisdictions.

When it updates

CDC updates these counts once a week, with data as of noon on Thursday. This page reads CDC's data every few hours and updates at the same address after each CDC update.

The most common symptoms of norovirus are diarrhea, vomiting, nausea and stomach pain, according to the Centers for Disease Control and Prevention. The agency lists fever, headache and body aches as other symptoms. This page reports what the CDC states and is not personal medical advice.

When symptoms start and how long they last

The first two rows come from the CDC's About Norovirus page. The third comes from its page on how norovirus spreads, which also says a person is most contagious while having symptoms and during the few days after feeling better.

The CDC describes norovirus as a very contagious virus that causes acute gastroenteritis, an inflammation of the stomach or intestines. The agency says it is sometimes called the "stomach flu" or the "stomach bug" but is not related to the flu, which is caused by the influenza virus. For flu and other respiratory illness, see Is flu and respiratory illness high in my state?

Signs of dehydration

The CDC says a person with norovirus can vomit or have diarrhea many times a day, and that this can lead to dehydration, especially in young children, older adults and people with other illnesses. The agency lists these symptoms of dehydration:

• Decreased urination
• Dry mouth and throat
• Feeling dizzy when standing up
• In children, crying with few or no tears and unusual sleepiness or fussiness

The same page says there is no specific medicine to treat norovirus illness, and that antibiotics will not help because they fight bacteria, not viruses. The CDC's guidance is to drink plenty of liquids to replace fluid lost from vomiting and diarrhea. It says oral rehydration fluids sold over the counter are most helpful for mild dehydration, and that a person who thinks they or someone in their care is severely dehydrated should call a doctor.

How norovirus spreads

The CDC says norovirus spreads easily and quickly, and that a person can get it in different ways, including:

• Having direct contact with someone who has norovirus, such as caring for them, sharing food or eating utensils with them, or eating food they handled.
• Eating food or drinking liquids that are contaminated with norovirus.
• Touching contaminated objects or surfaces and then putting unwashed fingers in the mouth.

The agency's page on how the virus spreads says it takes only a few norovirus particles to make a person sick. Its prevention page says the virus can be found in vomit or feces even before a person starts feeling sick.

What the CDC says about prevention

The CDC's prevention page gives these steps:

• Wash hands often with soap and water for at least 20 seconds, especially after using the toilet or changing diapers and before eating, preparing or handling food. The agency says hand sanitizer does not work well against norovirus and is not a substitute for handwashing.
• Do not prepare or handle food or care for others while sick, and wait at least 2 days (48 hours) after symptoms stop.
• Wash fruits and vegetables well, and cook oysters and other shellfish thoroughly to an internal temperature of at least 145°F.
• After someone vomits or has diarrhea, clean and disinfect the entire area. The CDC says to use a chlorine bleach solution of 1,000 to 5,000 ppm, which it gives as 5 to 25 tablespoons of household bleach (5% to 8%) per gallon of water, or a disinfecting product registered with the Environmental Protection Agency against norovirus, and to leave bleach on the area for at least 5 minutes.
• Wash clothes or linens that may have vomit or feces on them with detergent and hot water at the maximum cycle length, then machine dry them at the highest heat setting.

Medicare open enrollment ends on December 7. The Centers for Medicare and Medicaid Services said the period runs from October 15 to December 7 every year, and Medicare.gov said a plan must get a request to join by December 7. On November 11, 2026, the Medicare.gov home page said open enrollment was under way through December 7 and that 2027 health and drug plans could be compared.

The dates

The dates in this table come from the Joining a plan page on Medicare.gov.

What can be changed before December 7

The agency said October 15 to December 7 is when all people with Medicare can change their Medicare health plans and prescription drug coverage for the following year. Medicare.gov lists three kinds of change for the period:

• Join, drop or switch to another Medicare Advantage Plan, with or without drug coverage.
• Switch from Original Medicare to a Medicare Advantage Plan, or from a Medicare Advantage Plan to Original Medicare.
• Join, drop or switch to another Medicare drug plan, for people in Original Medicare.

People whose current plan is still offered and still meets their needs do not need to do anything, the agency said.

After December 7

Two other periods on the same Medicare.gov page fall outside this window. The Medicare Advantage Open Enrollment Period, from January 1 to March 31, is only for people already in a Medicare Advantage Plan. They can switch to another Medicare Advantage Plan or drop the plan and return to Original Medicare, and those who return can also join a separate Medicare drug plan.

A Special Enrollment Period is available only in certain situations, such as moving to a new address or getting Extra Help to pay drug costs, and its timing varies, the page says.

This deadline is separate from the one for Marketplace plans, which is covered in When is the HealthCare.gov open enrollment deadline?

Open enrollment for 2027 health coverage on HealthCare.gov runs through January 15, 2027, the Centers for Medicare and Medicaid Services said in a fact sheet, and December 15 is the last day to enroll for coverage that starts January 1, according to the dates and deadlines page on HealthCare.gov. The federal government operates the Health Insurance Marketplace, available at HealthCare.gov, for most states, and some states run their own Marketplaces, the site's glossary says.

The dates for 2027 coverage

The agency said in the fact sheet, dated October 30, 2026, that the open enrollment period for 2027 HealthCare.gov coverage "begins on November 1, 2026, and runs through January 15, 2027." The HealthCare.gov schedule gives these steps.

What happens after the deadline

After January 15, a person can enroll in or change Marketplace plans only by qualifying for a Special Enrollment Period, HealthCare.gov says. The site describes that as a period outside open enrollment when a person can enroll because of a life event, such as getting married, having a baby, moving or losing health coverage. It also says people can apply for Medicaid or the Children's Health Insurance Program at any time.

States with their own Marketplace

These dates are the ones HealthCare.gov publishes. HealthCare.gov says that how a person applies depends on whether their state has its own Marketplace, and it directs people to pick their state to find out how to get coverage.

Find your state in the table above to see the level the Centers for Disease Control and Prevention reports for the most recent week. The key facts at the top count how many places fall at each level.

What the level measures

The agency rates each state with a measure it calls acute respiratory illness. In its description of the data, the agency says the measure "captures a broad range of diagnoses from emergency department visits for respiratory illnesses, from the common cold to severe infections like influenza, RSV and COVID-19." The level therefore describes all of those illnesses together and is not a count of flu cases alone.

How to read the table

The first column of levels is the most recent week the agency has published, and the date of that week is in the line under the key facts. "No data" means the agency reported no level for that place for the week.

The agency publishes only the current week, so the comparison with last week comes from the record this page keeps of each weekly release. Where that record has no level for a place for the week before, the table says "not in our history" and gives the direction as "new".

When it updates

The agency says the data are updated once a week, on Fridays. This page is updated at the same address after each release.

What this page is not

This page reports public health data and is not medical advice. The level for a state does not say whether any one person is ill or what that person should do, and questions about symptoms belong with a doctor or a local health department.