Influenza

Influenza Vaccination

Infectious disease

Hand Hygiene

Influenza is a viral infection that attacks your respiratory system — your nose, throat and lungs.

Influenza, commonly called the flu.

For most people, influenza resolves on its own.

But sometimes, influenza and its complications can be deadly.

Your best defense against influenza is to receive an annual vaccination.

Symptoms

Initially, the flu may seem like a common cold with a runny nose, sneezing and sore throat.

But colds usually develop slowly, whereas the flu tends to come on suddenly.

Flu develop worse symptoms than colds.

Common signs and symptoms of the flu include:

Fever over 100.4 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

Causes

Flu is a viral infection.

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.

Influenza viruses are constantly changing, with new strains appearing regularly. If you've had influenza in the past, your body has already made antibodies to fight that particular strain of the virus. If future influenza viruses are similar to those you've encountered before, either by having the disease or by vaccination, those antibodies may prevent infection or lessen its severity.m But antibodies against flu viruses you've encountered in the past can't protect you from new influenza subtypes that can be very different immunologically from what you had before.

Risk factors

Factors that may increase your risk of developing influenza or its complications include:

Age. Seasonal influenza tends to target young children and older adults.

Living or working conditions. People who live or work 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.

Pregnancy. Pregnant women are more likely to develop influenza complications, particularly in the second and third trimesters. Women who are two weeks postpartum are also more likely to develop influenza-related complications.

Obesity. People with a BMI of 40 or more have an increased risk of complications from the flu.

Complications

If you're young and healthy, seasonal influenza usually isn't serious. Although you may feel miserable while you have it, the flu usually goes away in a week or two with no lasting effects. But high-risk children and adults may develop complications such as:

Pneumonia
Bronchitis
Asthma flare-ups
Heart problems
Ear infections

Pneumonia is the most serious complication. For older adults and people with a chronic illness, pneumonia can be deadly.

Prevention

Influenza vaccination is available globally and it is recommended 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.

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 hygiene 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.

Diagnosis

Your doctor will conduct a physical exam, look for signs and symptoms of influenza, and possibly order a test that detects influenza viruses.

There are sensitive flu tests available in some specialized hospitals and labs. Your doctor may diagnose you with influenza based on symptoms

Treatment

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 (Tamiflu) or zanamivir (Relenza).