Influenza by Rosalyn Carson-DeWitt, MD

En Español (Spanish Version) More InDepth Information on This Condition

| Definition | Causes | Risk Factors | Symptoms | Diagnosis | Treatment | Prevention

Causes

The flu is caused by the influenza virus. Each winter, the virus spreads around the world. The strains are usually different from one year to the next. It is possible to get the flu even when it is not flu season although it is less likely.

The two main kinds of influenza virus are Type A and Type B.

Someone infected with the virus may sneeze or cough. This releases droplets into the air. If you breathe in infected droplets, you can become infected. You can also become infected through touch. If you touch a contaminated surface, you may transfer the virus from your hand to your mouth or nose.

Risk Factors

Factors that increase your chance of the flu include:

• Living or working in crowded group conditions, such as:
  • Nursing homes
  • Schools
  • Military forces
  • Daycare centers
• Being physically or mentally disabled—People with disabilities may not be able to easily communicate their symptoms or may have trouble practicing preventive measures against the flu, putting them more at risk.

Certain groups of people are at a higher risk of developing complications from the flu. Risk factors for complications include:

• Being 6 months to 4 years old
• Being 50 years old and older
• Having certain conditions, including chronic lung condition (eg, asthma ); cardiovascular disease; kidney, liver, neurological, blood, or metabolic condition (eg, diabetes)
• Having a suppressed immune system (eg, HIV )
• Being pregnant during the flu season
• Being 6 months to 18 years old and receiving long-term aspirin therapy (may be at risk for Reye's syndrome )
• Living in nursing homes or other long-term care facilities
• Being American Indian/Alaska Native
• Being severely obese

Symptoms

If you have the flu, you might infect others one day before symptoms start and up to five days (sometimes more) after you become sick. This means you may be infecting others even before you know you are sick.

Symptoms usually start abruptly. They may include:

• High fever and chills
• Severe muscle aches
• Severe fatigue
• Headache
• Decreased appetite or other gastrointestinal symptoms like nausea, vomiting, and diarrhea (more common in children than adults)
• Runny nose, nasal congestion
• Sneezing
• Watery eyes, conjunctivitis
• Sore throat
• Cough (can last for two or more weeks)
• Swollen lymph nodes in the neck

You may start to feel better in 7-10 days, but you may still have a cough and feel tired.

Diagnosis

The doctor will ask about your symptoms and medical history. Diagnosis of the flu is usually based on symptoms.

In some cases, your doctor may take samples from your nose or throat to confirm the diagnosis.

Treatment

Treatment may include:

Antiviral Prescription Medicines

Most people with the flu do not need antiviral medicine. If you have the flu, check with your doctor to see if you need antiviral medicine. You may need it if you are in a high-risk group or if you have a severe illness (like breathing problems).

Antiviral medicines generally may help relieve symptoms and shorten the time you are sick. They must be taken within 48 hours of the first symptoms.

Antiviral medicines include:

• Zanamivir (Relenza)—This may worsen asthma or chronic obstructive pulmonary disease (COPD).
• Oseltamivir (Tamiflu)—Some kinds of seasonal influenza virus are resistant to this drug.
• Amantadine (Symmetrel)—Some kinds of seasonal influenza virus are resistant to this drug.
• Rimantadine (Flumadine)—Some kinds of seasonal influenza virus are resistant to this drug.

Oseltamivir (and perhaps zanamivir) may increase the risk of self-injury and confusion shortly after taking, especially in children. Children should be closely monitored for signs of unusual behavior.

Rest

It is important to get plenty of rest when your body is fighting the flu.

Fluids

Drink a lot of liquids. This can include water, juice, and caffeine-free tea.

Over-the-Counter Pain Relievers

These medications are used to control fever and to treat aches and pains. Adults can use:

• Acetaminophen
• Ibuprofen

Decongestants

Decongestants are available as pills or nasal sprays. If you use a nasal spray, don't use it longer than 3-5 days. You may experience an increase in congestion when you stop using the spray. This is called rebound.

Cough Medicines

These include:

• Over-the-counter (OTC) cough and cold medicines, including decongestants, expectorants, antihistamines, and cough suppressants
  • OTC cough and cold products should not be used to treat infants or children less than two years old. Rare but serious side effects have been reported. They include death, convulsions, rapid heart rates, and decreased levels of consciousness. Serious side effects have also been reported in children aged 2-11 years. Research is still going on for the safety of OTC products for this age group.
• Prescription cough medicines
• Cough drops

Herbal Treatment

Elderberry extract may reduce flu symptoms. Researchers found that products containing elderberry, like Sambucol and ViraBLOC, decreased symptoms in some studies. But be aware that herbal remedies are not regulated by the government. So the herbal supplements that you buy may not have the same ingredients as those studied and they may contain impurities (things that should not be in the product).

If you are diagnosed with the flu, follow your doctor's instructions .

Prevention

Ways to Avoid Getting the Flu

The best way to prevent getting the flu is to get vaccinated. You will need to get vaccinated each year since the virus changes every season. Two forms of the vaccine are available: a flu shot (injection) and a nasal spray. You should get vaccinated between September and January (or later since the flu season can last much longer). The nasal spray is currently approved for healthy, non-pregnant people aged 2-49 years old.

People who care for those with severely weakened immune systems should not get the nasal spray. Instead they should get the flu shot.

The Centers for Disease Control and Prevention (CDC) recommend that anyone aged six months and older should get a flu vaccine.

It takes about two weeks for the vaccination to protect you against the flu.

There are people, however, who should not be vaccinated:

• Those who are severely allergic to chicken eggs
• Those who had a severe reaction to vaccination in the past
• Children less than six months old
• Those who are very sick and have a fever should discuss vaccination with a medical provider.

There are general measures you can take to reduce your risk of getting the flu:

• Wash your hands often, especially when you come in contact with someone who is sick. Wash your hands for 15-20 seconds with soap and water. Rubbing alcohol-based cleaners on your hands is also helpful.
• Avoid close contact with people who have respiratory infections. The flu can spread starting one day before and ending seven days after symptoms appear. If have to be in close contact with a sick person, wear a face mask or a disposable respirator.
• Cover your mouth and nose with a tissue when you cough or sneeze. Throw away the tissue after you use it. Coughing or sneezing into your elbow or upper sleeve is also helpful.
• Do not spit.
• Do not share drinks or personal items.
• Do not bite your nails or put your hands near your eyes, mouth, or nose.
• Keep surfaces clean by wiping them with a household disinfectant.

Sometimes it is beneficial to take antiviral medications to prevent the flu. You may want to talk with your doctor about taking antiviral medications to lower your risk of getting the flu if you are exposed to the flu and:

• Are at high risk for complications of the flu
• Are a healthcare worker, public health worker, or first responder

If you have the flu and live with someone who is at risk for complications (eg, elderly, babies, someone with cancer), that person may need to take antiviral medications to prevent getting the flu from you.

Remember that these medications are not a substitute for getting vaccinated. Vaccination is still the best way of preventing the flu.

Ways to Avoid Spreading the Flu

If you have the flu, take these steps to avoid spreading it to others:

• Avoid close contact with people. Before you can return to school or work, your fever should be gone for at least 24 hours without the help of fever-reducing medicine. This could take up to seven days after symptoms first appear. It is important to stay home if you have the flu, leaving your house only to see your doctor.
• If you cannot avoid close contact, cover your mouth and nose with a face mask.
• Wash your hands for 15-20 seconds with soap and water. Even if someone in your house has the flu, you may be able to avoid getting sick by washing your hands. Using a hand sanitizer is also helpful.
• Cover your mouth and nose with a tissue when you cough or sneeze. Throw away the tissue after you use it. Coughing or sneezing into your elbow or upper sleeve will also keep you from spreading the flu with your hands. Do not spit.
• Do not share drinks or personal items.
• Wash eating utensils with hot water and soap.
• Do not bite your nails or put your hands near your eyes, mouth, or nose.
• Keep surfaces clean by wiping them with a household disinfectant.
• Use the hot setting on your washing machine when washing infected laundry.