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Dive into the world of influenza viruses with CDC's in-depth guide. Learn about flu strains, mutations, and how they impact public health. Stay informed with the latest research.
Influenza, commonly known as flu, is caused by influenza viruses that affect the respiratory tract. These viruses are categorized into three types: A, B, and C. Type A is known for causing seasonal epidemics and pandemics, with its subtypes determined based on two proteins on the virus surface, hemagglutinin (H) and neuraminidase (N). Type B viruses circulate among humans and are usually less severe than Type A, yet they can also cause illness. Type C viruses are milder and not known to cause epidemics. Understanding these viruses and their subtypes is crucial for the development of effective vaccines and treatments each flu season.