What is the Flu? Symptoms, Causes, & Treatment

The flu is a contagious respiratory illness caused by influenza viruses that infect your nose, throat, and sometimes your lungs. Unlike a common cold, the flu typically hits you suddenly and can make you feel quite sick for several days to weeks.

Most people recover completely from the flu, but it's worth understanding what you're dealing with. The flu spreads easily from person to person and tends to circulate more during fall and winter months, though you can catch it any time of year.

What are the symptoms of the flu?

Flu symptoms usually appear suddenly, often within one to four days after you've been exposed to the virus. You might wake up feeling fine and then feel terrible by afternoon, which is one way the flu differs from a cold that develops gradually.

The most common symptoms you might experience include:

• Fever (usually 100°F or higher)
• Body aches and muscle soreness
• Headache
• Extreme tiredness and weakness
• Dry cough
• Sore throat
• Runny or stuffy nose
• Chills

Some people, especially children, may also experience nausea, vomiting, or diarrhea, though these symptoms are more common with stomach flu (which isn't actually influenza). Your fever typically lasts three to four days, but you might feel tired and weak for several weeks as your body fully recovers.

What causes the flu?

The flu is caused by influenza viruses, which are tiny germs that invade the cells in your respiratory system. There are four main types of influenza viruses, but types A and B are the ones that cause seasonal flu outbreaks each year.

These viruses spread primarily through tiny droplets that infected people release when they cough, sneeze, or talk. You can catch the flu by breathing in these droplets or by touching a surface that has the virus on it and then touching your mouth, nose, or eyes.

What makes the flu tricky is that people can spread it to others starting about one day before symptoms appear and up to seven days after becoming sick. This means someone might pass the flu to you before they even know they have it.

What are the types of flu?

There are four types of influenza viruses, but you'll mainly encounter two of them during flu season. Understanding these types can help you make sense of why you need a new flu shot each year.

Influenza A is the most common type and causes the seasonal flu outbreaks that happen every year. This type can infect humans, birds, and pigs, and it's constantly changing, which is why scientists have to update the flu vaccine annually.

Influenza B also causes seasonal outbreaks but tends to be milder than type A. It only infects humans and seals, so it doesn't change as rapidly as type A, but it still mutates enough to require yearly vaccine updates.

Influenza C causes only mild respiratory symptoms and doesn't lead to epidemics. Influenza D primarily affects cattle and isn't known to infect humans, so you don't need to worry about these last two types.

When should you see a doctor for the flu?

Most healthy people can recover from the flu at home with rest and supportive care. However, you should contact your doctor if you develop certain warning signs or if you're at higher risk for complications.

Seek medical attention right away if you experience:

• Difficulty breathing or shortness of breath
• Persistent chest pain or pressure
• Sudden dizziness or confusion
• Severe or persistent vomiting
• Flu symptoms that improve but then return with fever and worse cough
• High fever (over 103°F) that doesn't respond to fever reducers

You should also call your doctor if you're in a high-risk group, even if your symptoms seem mild. High-risk individuals include adults over 65, pregnant women, young children under 5, and people with chronic conditions like asthma, diabetes, or heart disease.

What are the risk factors for the flu?

Anyone can catch the flu, but certain factors can increase your chances of getting sick or developing serious complications. Age plays a significant role, with children under 5 and adults over 65 being at higher risk.

Your overall health status matters too. People with chronic conditions face greater risks:

• Asthma or other lung diseases
• Heart disease
• Diabetes
• Kidney or liver disorders
• Weakened immune system from medications or illness
• Extreme obesity (BMI of 40 or higher)

Pregnant women are also at increased risk, particularly during the second and third trimesters. Living or working in crowded environments like nursing homes, schools, or military barracks can increase your exposure risk.

What are the possible complications of the flu?

While most people recover from the flu without lasting problems, complications can occur, especially in high-risk individuals. Understanding these possibilities can help you know when to seek additional medical care.

The most common complication is bacterial pneumonia, which can develop when bacteria infect your lungs while they're weakened by the flu virus. You might notice worsening symptoms after initially feeling better, including increased coughing, chest pain, or difficulty breathing.

Other complications can include:

• Sinus infections
• Ear infections
• Worsening of chronic conditions like asthma or diabetes
• Heart problems, including heart attacks (rare)
• Brain inflammation (extremely rare)
• Muscle breakdown leading to kidney problems (very rare)

Most complications are treatable when caught early, which is why it's important to stay in touch with your healthcare provider if you're at higher risk or if your symptoms worsen after initially improving.

How can the flu be prevented?

The good news is that you can take several effective steps to protect yourself and others from the flu. The annual flu vaccine is your best defense, reducing your risk of getting the flu by 40-60% when the vaccine is well-matched to circulating viruses.

You should get vaccinated by October if possible, though getting vaccinated later still provides protection. The vaccine is recommended for everyone 6 months and older, with rare exceptions for people with severe allergies.

Daily preventive actions can also help protect you:

• Wash your hands frequently with soap and water for at least 20 seconds
• Avoid touching your eyes, nose, and mouth
• Stay away from people who are sick when possible
• Clean and disinfect frequently touched surfaces
• Maintain good general health through adequate sleep, physical activity, and nutritious foods

If you do get sick, stay home for at least 24 hours after your fever is gone to avoid spreading the flu to others.

How is the flu diagnosed?

Your doctor can often diagnose the flu based on your symptoms and the time of year, especially during flu season when the virus is circulating widely in your community. The sudden onset of fever, body aches, and respiratory symptoms typically points to influenza.

Sometimes your doctor might want to confirm the diagnosis with a rapid flu test, which involves swabbing your nose or throat. These tests can provide results in about 15 minutes, though they're not always 100% accurate.

More sensitive tests are available that can detect flu viruses more reliably, but results may take a few days. Your doctor will usually only order these if the results would change your treatment plan or if there's an outbreak they need to track.

What is the treatment for the flu?

Treatment for the flu focuses on helping you feel more comfortable while your body fights off the virus. Most people recover with supportive care at home, though antiviral medications can help in certain situations.

Antiviral drugs like oseltamivir (Tamiflu) or baloxavir (Xofluza) can shorten your illness by about one day if started within 48 hours of symptom onset. Your doctor might prescribe these if you're at high risk for complications or if you're severely ill.

For symptom relief, you can use:

• Acetaminophen or ibuprofen for fever and aches
• Throat lozenges or warm salt water gargles for sore throat
• Humidifiers or steam to ease congestion
• Plenty of fluids to prevent dehydration

Avoid giving aspirin to children or teenagers with flu symptoms, as this can lead to a rare but serious condition called Reye's syndrome.

How can you take care of yourself at home during the flu?

Taking care of yourself at home is often the best approach for flu recovery. Your body needs time and energy to fight off the virus, so rest is absolutely essential during the first few days when you feel worst.

Stay hydrated by drinking plenty of fluids like water, herbal teas, or clear broths. Warm liquids can be especially soothing for your throat and may help loosen congestion. Avoid alcohol and caffeine, which can contribute to dehydration.

Create a comfortable environment for recovery:

• Keep your room at a comfortable temperature
• Use extra pillows to elevate your head while sleeping
• Run a humidifier or breathe steam from a hot shower
• Eat light, nutritious foods when you feel up to it
• Take time off work or school to rest properly

Monitor your symptoms and don't rush back to normal activities too quickly. Even after your fever breaks, you might feel tired for several days or weeks as your body fully recovers.

How should you prepare for your doctor appointment?

If you need to see your doctor for flu symptoms, a little preparation can help make your visit more productive. Write down when your symptoms started and how they've progressed, as this timeline can help your doctor assess your condition.

Make a list of all your symptoms, even ones that might not seem related to the flu. Include your temperature readings if you've been checking your fever, and note any medications you've tried and whether they helped.

Bring important information with you:

• List of current medications and supplements
• Your vaccination history, including when you last got a flu shot
• Any chronic health conditions you have
• Recent travel or exposure to sick people

Don't forget to mention if you're pregnant, planning to become pregnant, or breastfeeding, as this affects treatment recommendations. Arrive a few minutes early and consider wearing a mask to protect others in the waiting room.

What's the key takeaway about the flu?

The flu is a common but potentially serious illness that affects millions of people each year. While it can make you feel quite sick for several days, most healthy people recover completely with proper rest and supportive care.

Your best protection is getting an annual flu vaccine and practicing good hygiene habits. If you do get sick, listen to your body, rest when you need to, and don't hesitate to contact your doctor if you're at high risk or if your symptoms worsen.

Remember that the flu is highly contagious, so staying home when you're sick protects not just your own recovery but also your community's health. With the right care and precautions, you can get through flu season safely and help protect those around you too.