WHO fact sheet on influenza: includes key facts, definition, symptoms, transmission, seasonal epidemics, effects, prevention, WHO response.

Seasonal influenza (‘the flu’) is an acute respiratory infection caused by influenza viruses that circulate globally and year-round. It can cause illness ranging from mild to severe, sometimes resulting in hospitalization or death. Seasonal influenza activity has increased globally in recent months, with an increased proportion of seasonal influenza A(H3N2) viruses being detected. This ...

Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. It is characterized by a sudden onset of fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and a runny nose. The cough can be severe and can last two or more weeks.

Influenza is an acute viral infection that primarily attacks the upper respiratory tract, including the nose, throat, bronchi and, less frequently, the lungs. The disease occurs worldwide and spreads very quickly in populations, especially in crowded circumstances. In the northern hemisphere, annual influenza epidemics occur during autumn and winter affecting approximately 5-15% of the ...

Influenza is sweeping across the European Region earlier than usual, with a newly dominant virus strain placing health systems under significant pressure in some countries. The public is recommended to take simple protective action to keep themselves and others safe this winter.

Influenza, or the flu, is both a seasonal and a pandemic virus. Every year, mainly during the winter season, seasonal influenza infects as many as 1 billion people. This makes it one of the most common infectious respiratory viruses, after the common cold. Thankfully, the WHO Global Influenza Surveillance and Response System, or GISRS, monitors what viruses are circulating and twice a year ...

Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness. The virus is transmitted easily from person to person via droplets. Influenza tends to spread rapidly in seasonal epidemics. Infection usually lasts for about a week, and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive ...

The World Health Organization (WHO) today announced recommendations for the viral composition of influenza (or “flu”) vaccines for the 2026-2027 northern hemisphere influenza season. The announcement was made following a 4-day consultation examining global influenza surveillance data.

Since the official start of the seasonal influenza epidemic in late November 2024, indicators of respiratory infections have continued to rise across the WHO European Region. While the magnitude of the influenza season is within the expected range, it is important for health authorities and individuals to remain active in limiting the spread and protecting the most vulnerable, which includes ...

概述 季节性流感（流感）是由流感病毒引起的急性呼吸道感染。季节性流感在世界各地都很常见。大多数人不治而愈。 当人们咳嗽或打喷嚏时，流感很容易在人与人之间传播。接种疫苗是预防这种疾病的最佳方法。 流感的症状包括急性发烧、咳嗽、喉咙痛、身体疼痛和乏力。 治疗应以缓解症状为 ...