Influenza (Flu)

Influenza, commonly called "the flu," is an illness caused by viruses that infect the respiratory tract. Compared with most other viral respiratory infections, such as the common cold, influenza (flu) infection often causes a more severe illness.

At least 20 million people, including 500,000 U.S. citizens, died in the 1918 influenza pandemic. Today, as many as 36,000 Americans continue to die each year of what's commonly known as the flu, and more than 200,000 are hospitalized. Most outbreaks in North America occur between October and May. The peak season is usually late December to early March.

Anyone can get influenza, a viral infection that attacks your respiratory system, including your nose, throat, bronchial tubes and lungs. You're especially at risk if you are an older adult, have diabetes , chronic heart or lung disease, or an impaired immune system.

Signs and Symptoms

The flu virus attacks your respiratory system. This leads to the symptoms you commonly experience with the flu. Some signs and symptoms, such as a runny nose, sneezing and sore throat, may initially seem like a common cold. But if you are an adult and have a fever of 101 F or more, you may have influenza. Your fever may last from one day to as long as a week and, in rare cases, may reach as high as 106 F.
You're also likely to feel much worse with the flu than with a cold. Although you can probably carry on with a cold, the flu can knock you flat. Even after you've recovered, you may still feel tired.
Other signs and symptoms of influenza include:

• Chills and sweats
• Headache
• Dry cough
• Muscular aches and pains, especially in your back, arms and legs
• Fatigue and weakness
• Nasal congestion
• Loss of appetite

Children with the flu tend to have higher fevers than infected adults have — often 103 to 105 F. Influenza may also cause children to feel nauseous and experience vomiting and diarrhea.
The flu virus typically has an incubation period of one to four days, although symptoms usually come on suddenly. In most cases, you should feel better in about a week to 10 days unless you develop a serious post-flu lung infection, such as bacterial pneumonia or subacute bronchitis — an inflammation of the lining of your bronchial tubes.
If you've been infected with the flu, you can spread the disease to others before you realize you're sick and for as long as a week after your symptoms appear.

Distinguishing flu from other ailments.
Although other viral infections, especially colds and intestinal ailments such as gastroenteritis — a condition that causes diarrhea, nausea and vomiting — are often referred to as the flu, they're not. Real influenza usually doesn't affect your intestines. And while you may cough and sneeze with the flu, you're also likely to have a high fever, chills and body aches — signs and symptoms you won't typically have with a cold.

More about Flu

Causes

Responsible for epidemics of respiratory illness that occur almost every winter and are often associated with increased rates of hospitalization and death. Influenza type C differs from types A and B in some important ways. Type C infection usually causes either a very mild respiratory illness or no symptoms at all; it does not cause epidemics and does not have the severe public health impact that influenza types A and B do. Efforts to control the impact of influenza are aimed at types A and B.

Once you've had the flu, you develop antibodies to the virus that caused it, but those antibodies won't protect you from new strains. And although outbreaks in different regions generally vary in their duration and severity, the fact that millions of people travel every day means that regional strains of flu can show up just about anywhere.

Risk Factors

Children ages 6 months to 2 years and people older than 65 are considered at high risk of complications from influenza. You're also at increased risk of influenza or its complications if you:

• Are a resident of a nursing home or other chronic-care facility.
• Have a chronic disorder such as diabetes or heart, kidney or lung conditions. People with diabetes are at greater risk of complications of flu, such as pneumonia, and are three times more likely to die of flu than are people without diabetes.
• Have a weakened immune system from infection with the human immunodeficiency virus (HIV), leukemia or medications you take following an organ transplant.
• Will be in your second or third trimester of pregnancy during flu season.
• Work in a health care facility where you're more likely to be exposed to the flu virus.
• Are in regular, close contact with children age 2 or younger.

Children are at high risk if they:

• Have asthma or another chronic lung condition.
• Have cardiovascular disease. Children with cardiovascular disease may have a passive congestion of their lungs, which makes them more susceptible to viral illnesses.
• Are taking medications to suppress their immune systems.
• Have sickle cell anemia, HIV infection, diabetes, chronic kidney disease, chronic metabolic diseases or are on long-term aspirin therapy
• Aspirin therapy puts children age 16 and under at risk of Reye's syndrome, a rare but potentially fatal disease.
  

Diagnosis
Your health care provider will probably be able to diagnose your case of flu from a physical examination and a description of your symptoms. He or she may take a chest X ray if there is concern about complications such as pneumoniaTreatment Approach
The most important aspect of treatment is rest and fluids. Taking mild pain medication, available without a prescription, can help relieve muscle aches and pains. If you are at high risk for complications (see Risk Factors), then antiviral medications (drugs that fight the virus) may shorten the duration of your symptoms, but they need to be started within 48 hours of the start of the illness.
Medications

Influenza (Flu) Medications

• Tamiflu