By Mayo Clinic Staff

Call your healthcare professional if you think you have the flu and you or someone you're caring for is at high risk of serious flu illness, or flu-related complications.

Unlike a cold, the flu tends to come on suddenly and makes you feel much worse than a cold. Common symptoms of the flu often include a fever but not always, as well as headache, aching muscles, and chills and sweats.

Other symptoms include:

• Dry, persistent cough.
• Shortness of breath.
• Tiredness and weakness.
• Runny or stuffy nose.
• Sore throat.
• Eye pain.

Vomiting and diarrhea also are symptoms of the flu but this is more common in children than adults.

Factors that can raise your risk of getting serious flu or flu-related complications include:

• Age. Seasonal flu tends to be more serious in young children, especially those age 12 months or younger, and adults older than age 65.
• Living or working conditions. People who live or work in facilities with many other residents, such as nursing homes, are more likely to develop the flu. People who are staying in the hospital also are at higher risk.
• Weakened immune system. Some treatments, medications and diseases make it easier to catch the flu and may raise the risk of complications from the flu. Examples are cancer treatments, organ transplant medications, long-term use of steroids and HIV/AIDS.
• Chronic illnesses. Conditions such as asthma and other lung diseases, diabetes, heart disease, nervous system diseases, metabolic disorders, problems with an airway, and kidney, liver or blood disease increase the risk of flu complications.
• Race. In the United States, American Indian or Alaska Native people, Black people and Latino people all may have an increased risk of influenza complications.
• Aspirin use under age 20. People who are younger than 20 years of age and are receiving long-term aspirin therapy are at risk of developing Reye's syndrome if infected with influenza.
• Pregnancy. Being pregnant or giving birth during flu season raises a person's risk for flu complications.
• Obesity. People with a body mass index (BMI) of 40 or higher have an increased risk of flu complications.

Complications of flu include pneumonia, sinus or ear infections, bronchitis, and acute respiratory distress syndrome. The flu also can lead to inflammation of the heart, brain or muscles.

And flu infection can worsen chronic health problems such as asthma and congestive heart failure. These illnesses may need to be treated in the hospital and, rarely, may lead to death.

Treating flu for people at high risk

If you're in one of these groups or you have serious symptoms linked to flu infection, your doctor may prescribe an antiviral medicine. Examples include oseltamivir (Tamiflu), baloxavir (Xofluza), zanamivir (Relenza) or peramivir (Rapivab). These medicines may shorten your illness by a day or so and help prevent serious complications.

Not at high risk?

Most people with the flu have a mild illness and don't need to see a healthcare professional. With some rest and self-care measures at home, the average healthy person can expect to feel better within a week, although a dry cough may last for several weeks.

No matter your risk, if you have emergency symptoms of the flu, get medical care right away. For adults, emergency symptoms can include:

• Difficulty breathing or shortness of breath.
• Chest pain.
• Ongoing dizziness.
• Seizures.
• Worsening of existing medical conditions.
• Severe weakness or muscle pain.

Emergency symptoms in children include all of the symptoms seen in adults, as well as:

• Fast breathing or ribs that pull in with each breath.
• Gray or blue lips or nail beds.
• No tears when crying and a dry mouth, along with not needing to urinate.
• Symptoms, such as fever or cough, that get better but then come back or get worse.

These are just some of the emergency symptoms of flu. If you are worried about any symptom, contact a healthcare professional and get care right away.