What is seasonal influenza?

Seasonal influenza (or “flu”) is most often caused by type A or B influenza viruses. Symptoms include sudden onset of fever, cough (usually dry), headache, muscle and joint pain, sore throat, and a runny nose. The cough can be severe and can last 2 or more weeks. Most people recover from fever and other symptoms within a week without requiring medical attention. However, influenza can cause severe illness or death in high-risk groups.

Seasonal epidemics occur mainly during winter, from October to March in the northern hemisphere and April to September in the southern hemisphere. In tropical and subtropical countries, seasonal influenza can happen all year round.

How can I avoid getting the flu?

The best way to avoid getting the flu is to get the flu vaccine every year. Influenza viruses evolve constantly, and twice a year WHO makes recommendations to update the vaccine compositions. For the 2016-2017 northern hemisphere influenza season, the vaccine formulation was updated in February 2016 to contain two type A viruses (H1N1 and H3N2), and a type B virus.

WHO recommends annual vaccination for high-risk groups including health care workers. People should ideally get vaccinated just before the influenza season begins for the most effective coverage, although getting vaccinated at any time during the influenza season can still help prevent flu infections.

How is it treated?

People with the flu should drink plenty of water and rest. Most people will recover within a week. Antiviral drugs for influenza can reduce severe complications and deaths although influenza viruses can develop resistance to the drugs. They are especially important for high-risk groups. Ideally these drugs need to be administered early (within 48 hours of onset of symptoms). Antibiotics are not effective against influenza viruses.