Influenza B is a type of virus that causes seasonal flu, primarily affecting humans. Unlike Influenza A, which can infect various animals, Influenza B is more specific to humans and is generally less severe. It can lead to symptoms such as fever, cough, sore throat, and body aches. There are two main lineages of Influenza B: B/Yamagata and B/Victoria. Vaccines are available to help protect against Influenza B and are updated annually to match circulating strains. Preventive measures, such as handwashing and vaccination, are essential to reduce the spread of this virus.