Influenza (Flu)

Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. Influenza is commonly called the flu, but it's not the same as stomach "flu" viruses that cause diarrhea and vomiting.

For most people, influenza resolves on its own. But sometimes, influenza and its complications can be deadly. People at higher risk of developing flu complications include:

• Young children under age 5, and especially those under 12 months

• Adults older than age 65

• Residents of nursing homes and other long-term care facilities

• Pregnant women and women up to two weeks postpartum

• People with weakened immune systems

• People who have chronic illnesses, such as asthma, heart disease, kidney disease, liver disease and diabetes

• People who are very obese, with a body mass index (BMI) of 40 or higher

Though the annual influenza vaccine isn't 100 percent effective, it's still your best defense against the flu.

Symptoms

Initially, the flu may seem like a common cold with a runny nose, sneezing and sore throat. But colds usually develop slowly, whereas the flu tends to come on suddenly. And although a cold can be a nuisance, you usually feel much worse with the flu.

Common signs and symptoms of the flu include:

• Fever over 100.4 F (38 C)

• Aching muscles

• Chills and sweats

• Headache

• Dry, persistent cough

• Fatigue and weakness

• Nasal congestion

• Sore throat

When to see a doctor

Most people who get the flu can treat themselves at home and often don't need to see a doctor.

If you have flu symptoms and are at risk of complications, see your doctor right away. Taking antiviral drugs may reduce the length of your illness and help prevent more-serious problems.