Flu Symptoms & Severity

Influenza Symptoms

Content Source: Centers for Disease Control and Prevention

Influenza (also known as the flu) is a contagious respiratory illness caused by flu viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly. People who have the flu often feel some or all of these symptoms:

• Fever* or feeling feverish/chills
• Cough
• Sore throat
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue (tiredness)
• Some people may have vomiting and diarrhea, though this is more common in children than adults.

* It's important to note that not everyone with flu will have a fever.

Flu Complications

Most people who get influenza will recover in a few days to less than 2 weeks, but some people will develop complications (such as pneumonia) as a result of the flu, some of which can be life-threatening and result in death.

Pneumonia, bronchitis, and sinus and ear infections are three examples of complications from flu. The flu can make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.

People at Higher Risk from Flu

Anyone can get the flu (even healthy people), and serious problems from influenza can happen at any age, but some people are at higher risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant women, and young children are more likely to get complications from influenza.

Flu Severity

Flu is unpredictable and how severe it is can vary widely from one season to the next depending on many things, including:

• what flu viruses are spreading,
• how much flu vaccine is available
• when vaccine is available
• how many people get vaccinated, and
• how well the flu vaccine is matched to flu viruses that are causing illness.

One study found that during the 1990s, flu-related deaths ranged from an estimated 17,000 during the mildest season to 52,000 during the most severe season (36,000 average). Over a period of 31 seasons between 1976 and 2007, estimates of flu-associated deaths range from a low of about 3,000 to a high of about 49,000 people. During a regular flu season, about 90 percent of deaths occur in people 65 years and older. During 2009-2010, a new and very different flu virus (called 2009 H1N1) spread worldwide causing the first flu pandemic in more than 40 years. It is estimated that the 2009 H1N1 pandemic resulted in more than 12,000 flu-related deaths in the U.S. In contrast to seasonal flu, nearly 90 percent of the deaths occurred among people younger than 65 years of age. Overall, people between the ages of 50 and 64 were the most hard hit by 2009 H1N1 with about 80 percent of these people having one or more underlying health conditions.