How are influenza viruses classified?

What causes it? • Influenza virus. • Can be caused by a virus, bacteria, or fungi. What are the symptoms? What is the flu? · How does the flu spread? · Does your child need a flu vaccine every year? · Are some children more likely to have serious health problems caused ... Influenza viruses cause the flu. There are four types of flu viruses: influenza A, B, C and D.6 The viruses tend to change in two ways: antigenic drift and ... Oct 2, 2017 ... The flu is a highly contagious disease caused by the influenza virus. The virus enters your body through your nose, eyes or mouth. Jan 15, 2019 ... Colds and the flu are both caused by viruses, but not the same virus. They have similar symptoms and both affect the respiratory system. Oct 1, 2006 ... Colds and the flu cause many of the same symptoms. But colds are usually mild, while the flu tends to be more severe. Mar 21, 2025 ... The most severe influenza outbreak of the 20th century and, in terms of total numbers of deaths, among the most devastating pandemics in human history. Influenza is a respiratory illness caused by a virus. Any kind of infection, including the flu, can cause sepsis, the body's life-threatening response to ... The inflammation is caused by your immune system's response to a viral infection. “Some of the most common viruses associated with stomach flu are rotavirus and ... Jul 8, 2019 ... Equine influenza is a highly contagious respiratory disease of horses caused by subtypes of the influenza A virus.