Colds and influenza have some common symptoms, such as coughing and sneezing. Individuals with the flu, however, usually feel worse, take longer to fully recover and may experience other symptoms, such as:
- Chills and sweats
- Fever of 101 to 106 F
- Fever that lasts up to a week
- Loss of appetite
- Muscle aches (especially in the back, arms and legs)
- Sore throat
- Stuffy nose
Symptoms of the virus usually appear one to four days after exposure to the virus. Individuals generally feel better in one week to 10 days. Flu can lead to serious lung infections, such as pneumonia or swelling of the lining of the airways in the lungs (bronchitis).
Causes and Risk Factors
Influenza is caused by three types of viruses:
Influenza A, which was responsible for the deadly worldwide epidemic in 1918. These serious epidemics usually strike every 10 to 40 years.
Influenza B, which causes smaller epidemics that are limited to specific localities. These types of epidemics usually appear every three to 15 years. Because global travel is so much more accessible today, this type of influenza can quickly spread to other places.
Influenza C, which is rare and causes mild symptoms. It is fairly stable and unchanging.
Types A and B are continually changing, making it difficult to create a vaccine that protects against the flu from one year to the next.
After having a strain of influenza virus, a person's body develops antibodies to the virus that protect from getting that particular strain again. However, because the strains change so often, people tend to get the flu more than once.
People who are at greatest risk of complications from influenza include:
- Infants and children with chronic health problems, including asthma. These children may be more likely to have a severe illness if they contract the flu. It is especially important that they receive the vaccine.
- Adults 65 and older.
- Pregnant women.
- People who have medical conditions that put them at higher risk for influenza-related complications. This includes people with asthma, diabetes, heart disease and cancer.
Individuals who suspect that they have the flu should see their doctor as soon as possible, especially if they're at high risk. People with serious symptoms, such as difficulty breathing, severe sore throat, coughing that produces a lot of green or yellow fluid or feelings of being faint, should see a doctor quickly. Other serious signs include severe cough, high fever and sharp pain when breathing deeply.
Having a flu shot each year may help lower your risk of catching influenza. The vaccine can be given to anyone who is 6 months or older.