Which type of influenza virus is considered the most lethal?

The most lethal type of influenza virus is Type A. This strain is known for its ability to cause severe illness and can lead to pandemics, as it is highly variable and can mutate easily. Type A viruses infect a wide variety of animals, including birds and pigs, which allows for the mixing of genetic material and the emergence of new strains. This zoonotic potential and adaptability make Type A particularly dangerous, as seen during significant outbreaks like the 1918 pandemic. In contrast, Type B and Type C viruses tend to cause milder illness and do not exhibit the same level of virulence or widespread impact on global health. Type B primarily affects humans and is generally not associated with pandemics, while Type C typically produces mild respiratory symptoms and is not known to cause epidemics. Therefore, the lethality of Type A and its capacity to cause widespread outbreaks solidify its status as the most dangerous among the influenza virus types.