FLU season has arrived!

Seasonal influenza is an acute viral infection caused by an influenza virus.

Signs and symptoms
Seasonal influenza is characterized by a sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and runny nose. Most people recover from fever and other symptoms within a week without requiring medical attention. But influenza can cause severe illness or death in people at high risk (see below). The time from infection to illness, known as the incubation period, is about two days.

Who is at risk?
Yearly influenza epidemics can seriously affect all age groups, but the highest risk of complications occur among children younger than age two, adults age 65 or older, and people of any age with certain medical conditions, such as chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes), or weakened immune systems.

Transmission
Seasonal influenza spreads easily and can sweep through schools, nursing homes or businesses and towns. When an infected person coughs, infected droplets get into the air and another person can breath them in and be exposed. The virus can also be spread by hands infected with the virus. To prevent transmission, people should cover their mouth and nose with a tissue when coughing, and wash their hands regularly.

Treatment
Antiviral drugs for influenza are available and effectively prevent and treat the illness. There are two classes of such medicines, 1) adamantanes (amantadine and remantadine), and 2) inhibitors of influenza neuraminidase (oseltamivir and zanamivir). Some influenza viruses develop resistance to the antiviral medicines, limiting the effectiveness of treatment.

Sesonal
Influenza epidemics occur yearly during autumn and winter in temperate regions. Illnesses result in hospitalizations and deaths mainly among high-risk groups (the very young, elderly or chronically ill). Worldwide, these annual epidemics result in about three to five million cases of severe illness, and about 250 000 to 500 000 deaths. Most deaths associated with influenza in industrialized countries occur among people age 65 or older.

Prevention
The most effective way to prevent the disease or severe outcomes from the illness is vaccination. Safe and effective vaccines have been available and used for more than 60 years. Among healthy adults, influenza vaccine can prevent 70% to 90% of influenza-specific illness. Among the elderly, the vaccine reduces severe illnesses and complications by up to 60%, and deaths by 80%.

Vaccination is especially important for people at higher risk of serious influenza complications, and for people who live with or care for high risk individuals.