Seasonal Influenza (Flu): Symptoms and Prevention With Annual Vaccination
Each year, the flu spreads quickly through schools, workplaces, and families. Knowing how to spot symptoms early, when to seek care, and how to protect yourself with an annual flu vaccine can lower your risk of severe illness and protect people around you.
Understanding Flu Symptoms
Common symptoms of the flu include:
- Fever or chills
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches
- Fatigue
- Some may experience vomiting and diarrhea, though this is more common in children than adults.
When to Seek Medical Care
If you or someone you know is experiencing severe symptoms such as difficulty breathing, chest pain, sudden dizziness, confusion, or persistent vomiting, it is important to seek medical attention immediately. Additionally, individuals at higher risk for complications should contact their healthcare provider promptly if flu symptoms develop.
Preventive Measures
Alongside vaccination, consider these preventive strategies:
- Practice good hand hygiene by washing hands frequently with soap and water.
- Avoid close contact with sick individuals.
- Cover your mouth and nose with a tissue or your elbow when coughing or sneezing.
- Stay home when feeling unwell to prevent spreading the virus.
Frequently Asked Questions (FAQs)
1. Who should get the flu vaccine?
Everyone aged 6 months and older is recommended to receive the flu vaccine, especially those at higher risk for complications, including young children, the elderly, pregnant women, and individuals with chronic health conditions.
2. When is the best time to get vaccinated?
The flu vaccine is best administered in the fall, ideally before the end of October, to ensure adequate protection before the flu season peaks.
3. Can I get the flu from the vaccine?
No, you cannot get the flu from the flu vaccine. Some people may experience mild side effects, such as soreness at the injection site or low-grade fever, but these are not symptoms of the flu.
4. What should I do if I get sick with the flu?
If you suspect you have the flu, rest, stay hydrated, and consider over-the-counter medications to alleviate symptoms. If symptoms worsen or if you are in a high-risk category, contact your healthcare provider for guidance.
Staying informed and proactive about seasonal influenza can greatly enhance your health and the well-being of those around you. Make sure to prioritize your annual flu vaccination and stay alert for any symptoms during flu season.
Seasonal influenza affects people of all ages and can lead to missed work or school, clinic visits, and hospital stays—especially for young children, older adults, pregnant people, and those with chronic conditions. Seasonal influenza continues to cause millions of cases annually, making annual flu vaccination a key preventive strategy. Timely information matters because starting antiviral treatment early, and getting vaccinated before flu activity rises, can prevent complications and save lives.
What Is Seasonal Influenza?
Seasonal influenza (the “flu”) is a contagious respiratory infection caused by influenza viruses, mainly types A and B. It affects the nose, throat, and lungs. Unlike a common cold, the flu often hits suddenly and can make even healthy people very sick.
Influenza viruses are always changing through a process called antigenic drift. Small genetic changes help the virus escape the immune system. This is why immunity from last year’s infection or vaccine may not fully protect you this year, and it is also why the flu vaccine is updated annually.
In many countries, the flu peaks in the fall and winter months, when people spend more time indoors and the air is drier. In tropical regions, flu can circulate year-round with several peaks. Flu activity can vary widely from year to year.
“Stomach flu” is a misleading term. True influenza is a respiratory illness. While some people—especially children—may have nausea or vomiting with the flu, most stomach symptoms are caused by other viruses, not the influenza virus.
The flu causes a significant health burden. In a typical U.S. season, there are millions of illnesses, hundreds of thousands of hospitalizations, and tens of thousands of deaths. The impact is higher in bad seasons or when certain strains spread easily.
Because the virus changes and spreads quickly, public health experts recommend annual flu vaccination for nearly everyone aged 6 months and older. Vaccination reduces your risk of getting sick, and it makes illness milder if you do get the flu.
Signs and Symptoms
The flu often starts suddenly. Most people feel fine one day, then develop symptoms over several hours the next. The incubation period is typically 1–4 days after exposure (about 2 days on average). People can spread the virus about one day before symptoms begin.
Common flu symptoms include:
- Fever or feeling feverish with chills
- Cough and sore throat
- Runny or stuffy nose
- Headache and muscle or body aches
- Marked fatigue (tiredness)
- Sometimes vomiting or diarrhea (more common in children)
Symptoms can overlap with other respiratory infections, such as COVID-19 or RSV. Compared with a cold, the flu usually brings higher fever, stronger body aches, and severe fatigue. A cold tends to come on more slowly with milder symptoms.
Older adults may not always have a high fever; they might show confusion, weakness, or a sudden decline in function. Children can develop high fevers and may have ear pain or croup-like symptoms. People with asthma may notice wheezing or shortness of breath.
Most people begin to feel better within 3–7 days, but cough and fatigue can last two weeks or longer. Returning to normal activity too quickly can delay recovery and increase the chance of spreading the virus to others.
Pay attention to symptoms that get worse after a few days of improvement, as this pattern can suggest a secondary bacterial infection, such as pneumonia or sinusitis. Seek medical advice if you are in a higher-risk group or feel very unwell.
Causes and Transmission
Seasonal flu is caused by influenza A and B viruses. Influenza A subtypes (like H1N1 and H3N2) and influenza B lineages change over time. Seasonal changes (drift) are common; major genetic shifts (which can cause pandemics) are different events and not part of typical seasonal flu.
The flu spreads mainly through respiratory droplets and aerosols produced when an infected person coughs, talks, sneezes, or breathes. These particles can be inhaled by people nearby. The virus can also land on surfaces; touching a contaminated surface and then your eyes, nose, or mouth can lead to infection.
People are typically contagious from about one day before symptoms start to 5–7 days after they begin. Children and people with weakened immune systems can spread the virus for longer.
Environments with close contact—households, daycare centers, schools, college dorms, long-term care facilities, and crowded workplaces—are common settings for spread. Cold, dry air and poor ventilation help the virus travel farther and last longer.
Influenza viruses have animal reservoirs, including birds and pigs, and new strains can emerge. Seasonal influenza in people, however, is usually spread from person to person. You cannot get the flu from eating properly cooked poultry or pork.
Layered protections—annual vaccination, staying home when sick, masking in high-risk settings, hand hygiene, and improved ventilation—reduce transmission. Vaccination also lowers the amount of virus you shed if you do get infected.
Risk Factors
Anyone can get the flu, even healthy teens and adults. But some groups are more likely to develop severe illness, need hospital care, or have complications. Knowing your risk can help you act quickly if symptoms start.
Age plays a big role. Children under 5 years—especially under 2—and adults 65 years and older are at higher risk for complications such as pneumonia or dehydration.
Chronic medical conditions raise risk: asthma, COPD, heart disease, diabetes, kidney or liver disease, neurologic conditions, and metabolic disorders. People with a body mass index (BMI) ≥ 40 are also at higher risk of severe flu.
People with weakened immune systems—due to cancer treatment, transplants, advanced HIV, or immune-suppressing medications—are more likely to have severe or prolonged illness. Pregnant people and those up to two weeks postpartum also face higher risk.
Residents of nursing homes or other long-term care facilities are at elevated risk because of age, close living quarters, and existing health conditions. American Indian and Alaska Native communities have experienced higher rates of severe flu outcomes.
Work and living conditions matter too. Healthcare workers, teachers, childcare providers, and people in crowded housing face more exposures. Tobacco smoke and poor indoor air quality can worsen symptoms and lung irritation.
Skipping the annual flu vaccine increases your risk of infection and serious illness. Children 6 months through 8 years who have never been vaccinated need two doses the first season they are vaccinated for best protection.
Diagnosis and Testing
During flu season, clinicians often make a clinical diagnosis based on symptoms and local flu activity, especially when many people in the community have similar illness. Testing can help confirm the diagnosis and guide treatment, particularly for high-risk patients.
Rapid antigen tests, called rapid influenza diagnostic tests (RIDTs), can give results in minutes. They are easy to use but less sensitive, so false negatives can occur—especially later in the illness. They work best in the first 3–4 days of symptoms.
More accurate molecular tests detect viral genetic material, often by PCR (polymerase chain reaction) or other NAAT (nucleic acid amplification) methods. These tests are more sensitive and specific and can identify influenza A or B, and sometimes the subtype. A nasopharyngeal swab is commonly used.
Testing is most useful for people who are hospitalized, have severe or progressive disease, are at higher risk of complications, or when it will affect treatment decisions (for example, starting antivirals). Testing can also help distinguish flu from COVID-19 or RSV during periods when these viruses co-circulate.
If pneumonia is suspected, clinicians may order a chest X-ray, blood tests, and oxygen level measurements. These help assess severity and guide treatment, especially in older adults or those with underlying conditions.
Some FDA-authorized at-home combination tests can detect COVID-19 and influenza. If you use a home test, follow instructions exactly and contact your healthcare provider to interpret results and discuss treatment if you are at high risk or very sick.
Treatment and Home Care
Most people with uncomplicated flu can recover at home. Rest, fluids, and symptom relief are key. People at higher risk of complications, or anyone who is very sick, should contact a healthcare provider promptly—ideally within 48 hours of symptom start.
Prescription antiviral medications can shorten illness and lower the risk of complications, especially if started within 48 hours. Options include oral oseltamivir, inhaled zanamivir (not recommended for people with asthma or COPD), single-dose oral baloxavir, and IV peramivir for hospitalized patients. Starting antivirals later can still help if you are hospitalized or have severe or progressive disease.
At-home care and symptom relief:
- Drink plenty of fluids; use oral rehydration if needed.
- Use acetaminophen or ibuprofen for fever and aches (avoid aspirin in children and teens due to risk of Reye’s syndrome).
- Use a humidifier, warm fluids, and saline sprays for cough and congestion; honey can soothe cough in children over 1 year and adults.
- Rest and pace activity; avoid strenuous exercise until you are recovering.
- Use over-the-counter cold medicines carefully; ask your provider about safe choices for children, pregnancy, or chronic conditions.
Stay home while you are sick. Return to work or school after you are fever-free for at least 24 hours without fever-reducing medicine and your symptoms are improving. Consider wearing a mask for a few days after returning, especially around high-risk people.
Antibiotics do not treat the flu because it is caused by a virus. They are only needed if a bacterial infection develops, such as pneumonia or a severe sinus infection. Watch for fever or cough that returns or worsens after initial improvement.
Special situations need tailored care. Pregnant people should seek early treatment with oseltamivir, which is considered safe in pregnancy. Use weight-based dosing for children. Older adults and people with chronic illnesses may need closer monitoring and help with fluids and nutrition.
Prevention: Annual Flu Vaccination and Everyday Protection
Annual flu vaccination is the best way to prevent influenza and its complications. The CDC recommends vaccination for everyone aged 6 months and older, unless there is a specific contraindication. Vaccines include inactivated (IIV), recombinant (RIV), and live attenuated nasal spray (LAIV). Flu vaccines cannot give you the flu.
Get vaccinated by the end of October if possible, but vaccination later still helps. It takes about two weeks after the shot for protective antibodies to build. Children 6 months through 8 years who have never had a flu vaccine, or whose history is unclear, need two doses at least four weeks apart in the first season.
Vaccine effectiveness varies by year and by person, but vaccination consistently reduces the risk of infection, hospitalization, and death. Even if you get sick, you are likely to have a milder illness. Vaccination in pregnancy protects both the parent and the newborn for the first months of life through passive immunity.
Special vaccine options exist. Adults 65 and older should receive a higher-dose or adjuvanted flu vaccine if available. People with egg allergy can receive any flu vaccine; no extra safety steps are needed beyond standard precautions. The nasal spray (LAIV) is for non-pregnant, generally healthy people ages 2–49 and is not recommended for certain medical conditions. A history of Guillain-Barré syndrome within 6 weeks of a prior flu vaccine is a precaution—discuss risks and benefits with your provider.
In some situations—like outbreaks in nursing homes or after a household exposure—clinicians may recommend antiviral medicine to prevent flu (post-exposure prophylaxis). This is usually started within 48 hours of exposure for high-risk people.
Everyday protection tips:
- Wash hands often with soap and water or use hand sanitizer.
- Cover coughs and sneezes; wear a well-fitting mask in high-risk settings.
- Improve airflow: open windows, use exhaust fans, or consider HEPA filtration.
- Stay home when sick; keep distance from people who are ill.
- Clean high-touch surfaces regularly.
- Keep up with sleep, nutrition, and exercise to support your immune system.
Possible Complications
The most common serious complication is pneumonia. This can be caused directly by the flu virus or by bacteria (like Streptococcus pneumoniae or Staphylococcus aureus) taking advantage of the weakened lungs. Pneumonia can cause chest pain, shortness of breath, and low oxygen levels.
Influenza can worsen chronic illnesses. It can trigger asthma attacks, worsen COPD, and strain the heart in people with heart failure. The risk of a heart attack rises in the week after flu infection, especially in older adults and those with heart disease.
Other complications include sinus infections, ear infections (especially in children), severe dehydration, myositis (muscle inflammation), and rarely rhabdomyolysis (breakdown of muscle). Children can also have febrile seizures with high fever.
Inflammation can affect the heart (myocarditis) or the lining around the heart (pericarditis), and the brain (encephalitis). Guillain-Barré syndrome (GBS) is a rare nerve condition that can follow infections, including influenza. The risk of GBS after flu illness is higher than the small risk after flu vaccination.
Severe cases can lead to sepsis, acute respiratory distress syndrome (ARDS), and multi-organ failure. These emergencies require hospital care and sometimes intensive care.
Giving aspirin to children and teens with viral illnesses can lead to Reye’s syndrome, a rare but life-threatening condition affecting the liver and brain. Use acetaminophen or ibuprofen instead, and ask your provider about safe dosing.
When to Seek Medical Care or Emergency Help
If you are at higher risk for complications or feel very unwell, contact a healthcare provider as soon as flu symptoms begin. Early evaluation can confirm the diagnosis and start antiviral treatment quickly.
Adults should seek urgent or emergency care for:
- Trouble breathing, chest pain, or blue lips/face
- Confusion, fainting, seizures, or severe weakness
- Dehydration (very dry mouth, not urinating, dizziness)
- Persistent or very high fever (for example, 103°F/39.4°C or higher)
- Severe muscle pain, worsening cough, or coughing up blood
- Symptoms that improve but then return with worse fever or cough
Infants and children need urgent care for:
- Fast or labored breathing, ribs pulling in, or wheezing
- Blue or gray skin color; not waking, not interacting, or irritability
- Not drinking fluids, no tears when crying, or fewer wet diapers
- Fever in babies under 3 months (100.4°F/38°C or higher)
- Seizures, severe neck stiffness, or a rash with fever
- Symptoms that improve then worsen again
Pregnant people should call their obstetric provider promptly if they have flu symptoms. Watch for shortness of breath, chest pain, dehydration, or reduced fetal movement. Early antiviral treatment is recommended and safe in pregnancy.
Be alert for a second wave of symptoms. If you feel better and then develop high fever, worse cough, or chest pain, this may signal secondary bacterial pneumonia. Seek care quickly.
If you’re unsure about the best setting for care, start with telehealth or an urgent care clinic. Bring a list of your medications and conditions. Let the clinic know if you are immunocompromised or care for someone who is at high risk.
FAQ
Can the flu vaccine give me the flu?
No. Inactivated and recombinant vaccines do not contain live virus. The nasal spray uses a weakened virus that does not cause flu in healthy people. Mild side effects like soreness or low fever are possible.
When should I get the flu shot, and is it too late after October?
Get vaccinated by the end of October if you can. It’s still worthwhile to get vaccinated later, even in January or beyond, as long as flu viruses are circulating.
How effective is the flu vaccine?
Effectiveness varies each season. Even in years with lower match, vaccination reduces the risk of severe illness, hospitalization, and death. It can also make illness milder if you get sick.
Who should not get certain flu vaccines?
People with a severe allergy to a vaccine component or a previous severe reaction to a flu vaccine should not receive that vaccine. The nasal spray is not for pregnant people or those with certain chronic conditions. Discuss your situation with your provider.
I’m allergic to eggs. Can I get the flu vaccine?
Yes. People with egg allergy can receive any flu vaccine that is otherwise appropriate for their age and health. No special precautions are needed beyond routine ones.
Do antivirals really help, and when should I start them?
Yes. Antivirals work best if started within 48 hours of symptom onset, but they can still help later if you are very sick or hospitalized. Call your provider right away if you’re at higher risk.
What’s the difference between flu, a cold, and COVID-19?
Colds are usually milder and come on slowly. Flu often starts suddenly with high fever, aches, and fatigue. COVID-19 can look similar to flu; loss of taste or smell is more specific to COVID-19. Testing is the best way to know.
If I had the flu already this season, do I still need a vaccine?
Yes. You may have been infected by one strain, but the vaccine can protect against other strains that may circulate later.
Can I get the flu and COVID-19 shots at the same visit?
Yes. Co-administration is acceptable. You may have mild side effects like soreness or fatigue, but getting both is safe and convenient.
More Information
Centers for Disease Control and Prevention (CDC) – Seasonal Influenza: https://www.cdc.gov/flu
Mayo Clinic – Influenza (flu): https://www.mayoclinic.org/diseases-conditions/flu
MedlinePlus – Flu: https://medlineplus.gov/flu.html
Healthline – Flu: https://www.healthline.com/health/flu
WebMD – Influenza (Flu): https://www.webmd.com/cold-and-flu/flu
Thanks for reading. If this article helped you, please share it with friends and family, and talk with your healthcare provider about your personal flu risks and vaccination plan. For related health topics and local providers, explore more resources on Weence.com. Stay well and take good care.
