Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs. Influenza, commonly called the flu, is not the same as stomach “flu” viruses that cause diarrhea and vomiting.
For most people, influenza resolves on its own, but sometimes, influenza and its complications can be deadly. People at higher risk of developing flu complications include:
- Young children under 5, and especially those under 2 years
- Adults older than 65
- Residents of nursing homes and other long-term care facilities
- Pregnant women
- People with weakened immune systems
- People who have chronic illnesses, such as asthma, heart disease, kidney disease and diabetes
- People who are very obese, with a body mass index (BMI) of 40 or higher
Your best defense against influenza is to receive an annual vaccination.
Symptoms
Common signs and symptoms of the flu include:
- Fever over 100 F (38 C)
- Aching muscles, especially in your back, arms and legs
- Chills and sweats
- Headache
- Dry, persistent cough
- Fatigue and weakness
- Nasal congestion
- Sore throat
When to see a doctor
Most people who get the flu can treat themselves at home and often don’t need to see a doctor.
If you have flu symptoms and are at risk of complications, see your doctor right away. Taking antiviral drugs within the first 48 hours after you first notice symptoms may reduce the length of your illness and help prevent more-serious problem
Causes
Flu viruses travel through the air in droplets when someone with the infection coughs, sneezes or talks. You can inhale the droplets directly, or you can pick up the germs from an object — such as a telephone or computer keyboard — and then transfer them to your eyes, nose or mouth.
People with the virus are likely contagious from the day or so before symptoms first appear until about five days after symptoms begin, though sometimes people are contagious for as long as 10 days after symptoms appear. Children and people with weakened immune systems may be contagious for a slightly longer time.
Risk factors
Factors that may increase your risk of developing influenza or its complications include:
- Seasonal influenza tends to target young children and older adults.
- Living conditions. People who live in facilities along with many other residents, such as nursing homes or military barracks, are more likely to develop influenza.
- Weakened immune system. Cancer treatments, anti-rejection drugs, corticosteroids and HIV/AIDS can weaken your immune system. This can make it easier for you to catch influenza and may also increase your risk of developing complications.
- Chronic illnesses. Chronic conditions, such as asthma, diabetes or heart problems, may increase your risk of influenza complications.
- Pregnant women are more likely to develop influenza complications, particularly in the second and third trimesters.
- People with a BMI of 40 or more have an increased risk of complications from flu.
Treatments and drugs
Usually, you’ll need nothing more than bed rest and plenty of fluids to treat the flu. But in some cases, your doctor may prescribe an antiviral medication, such as oseltamivir or zanamivir. If taken soon after you notice symptoms, these drugs may shorten your illness by a day or so and help prevent serious complications.
Oseltamivir is an oral medication. Zanamivir is inhaled through a device similar to an asthma inhaler and shouldn’t be used by anyone with respiratory problems, such as asthma and lung disease.
Antiviral medication side effects may include nausea and vomiting. These side effects may be lessened if the drug is taken with food. Oseltamivir has also been associated with delirium and self-harm behaviors in teenagers.
Lifestyle and home remedies
If you do come down with the flu, these measures may help ease your symptoms:
- Drink plenty of liquids. Choose water, juice and warm soups to prevent dehydration.
- Get more sleep to help your immune system fight infection.
- Consider pain relievers. Use an over-the-counter pain reliever, such as acetaminophen or ibuprofen to combat the achiness associated with influenza. Don’t give aspirin to children or teens because of the risk of Reye’s syndrome, a rare, but potentially fatal disease.
Prevention
The Centers for Disease Control and Prevention recommends annual flu vaccination for everyone over the age of 6 months.
Each year’s seasonal flu vaccine contains protection from the three or four influenza viruses that are expected to be the most common during that year’s flu season. The vaccine is typically available as an injection or as a nasal spray.
Controlling the spread of infection
The influenza vaccine isn’t 100 percent effective, so it’s also important to take measures such as these to reduce the spread of infection:
- Wash your hands. Thorough and frequent hand-washing is an effective way to prevent many common infections. Or use alcohol-based hand sanitizers if soap and water aren’t readily available.
- Contain your coughs and sneezes. Cover your mouth and nose when you sneeze or cough. To avoid contaminating your hands, cough or sneeze into a tissue or into the inner crook of your elbow.
- Avoid crowds. Flu spreads easily wherever people congregate — in child care centers, schools, office buildings, auditoriums and public transportation. By avoiding crowds during peak flu season, you reduce your chances of infection. And, if you’re sick, stay home for at least 24 hours after your fever subsides so that you lessen your chance of infecting others.