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 from one day up to one 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 contracting influenza are those who:
- Are between the ages of six months and two years
- Are children with asthma or other chronic lung conditions
- Are in the fourth to ninth month of pregnancy
- Are older than 50
- Have a chronic disease, such as diabetes, heart disease or kidney or lung conditions (People with diabetes are more likely to have complications from influenza, such as pneumonia, and are three times more likely to die of flu than are other people.)
- Have a weakened immune system from HIV or AIDS, leukemia, chemotherapy or from taking anti-rejection medications after an organ transplant
- Have sickle-cell anemia
- Live in a nursing home or long-term care facility
Individuals who suspect that they have the flu should see their doctor as soon as possible, especially if 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 because these may be signs of bacterial pneumonia. 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 six months or older. Children who are not at risk but who spend a great deal of time with someone who is, such as a grandparent, may need to be vaccinated to prevent the spread of flu.