Flu (Influenza)

People who have the flu often experience

• Fever
• Feeling feverish/chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle aches
• Headaches
• Fatigue (tiredness)
• Vomiting and diarrhea (more common in children than adults)

Certain symptoms of the flu may signal an emergency and should be assessed by a medical professional.

In children, these include

• Fast breathing or trouble breathing
• Bluish skin color
• Not drinking enough fluids
• Not waking up or not interacting
• Irritability even when being held
• Improvement of flu-like symptoms followed by return of symptoms with fever and worse cough
• Fever with a rash

In infants, additional symptoms that could signal an emergency include

• Being unable to eat
• No tears when crying
• Significantly fewer wet diapers than normal

In adults, watch out for

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Sudden dizziness
• Confusion
• Severe or persistent vomiting
• Improvement of flu-like symptoms followed by return of symptoms with fever and worse cough

Flu is unpredictable. Its severity can vary widely from one season to the next depending on many factors, including

• What flu viruses are spreading
• How much flu vaccine is available
• When the vaccine is available
• How many people get vaccinated
• How well the flu vaccine matches the flu viruses that are causing illness

One study found that during the 1990s, flu-related deaths in the United States ranged from an estimated 17,000 during the mildest season to 52,000 during the most severe season, averaging 36,000 per year. Over a period of 31 flu seasons between 1976 and 2007, estimates of flu-associated deaths in the United States ranged from a low of about 3,000 to a high of about 49,000 people. During a typical flu season, about 90 percent of deaths occur in people age 65 and older.

Most people who get influenza will recover in less than two weeks, but some people will develop complications, some of which can be life-threatening or fatal. Complications can include bacterial pneumonia, ear or sinus infections, dehydration, and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes.

Complications usually appear after a person starts feeling better. After a brief period of improvement, the following symptoms may suddenly appear:

• High fever
• Shaking chills
• Chest pain with each breath
• Coughing that produces thick, yellow-greenish colored mucus

Reye's syndrome, a condition that affects the nerves, sometimes develops in children and teens who are recovering from the flu. Reye's syndrome begins with nausea and vomiting, but the progressive mental changes, such as confusion or delirium, cause the greatest concern.

The syndrome often begins in young people after they take aspirin to reduce fever or pain. Acetaminophen does not seem to be connected with Reye's syndrome.

Certain people are at greater risk for serious complications if they get the flu. These groups include

• Children younger than 5, especially children younger than 2 years old
• Newborn babies recently out of intensive care units
• Adults age 65 or older
• Pregnant women
• American Indians and Alaska Natives
• Those who are obese (Body Mass Index of 40 or greater)
• People younger than age 19 who are receiving long-term aspirin therapy
• People with certain medical conditions, including
  • Asthma, even if it's controlled or mild
  • Weakened immune function, including those with HIV/AIDS or cancer
  • Neurological conditions, including disorders of the brain, spinal cord, peripheral nerves, and muscle
  • Chronic lung disease, such as Chronic Obstructive Pulmonary Disease (COPD) and cystic fibrosis
  • Heart disease, such as congenital heart disease, congestive heart failure, and coronary artery disease
  • Blood disorders, such as sickle cell disease
  • Diabetes
  • Certain kidney, liver, and metabolic disorders