Influenza type B viruses are not classified by subtype and do not cause pandemics. Different strains of the flu virus mutate over time and replace the older strains. This is why it's important to ...
(NEXSTAR) – The flu is spreading far and wide ... about 97% have turned up positive for influenza A. Influenza A is further divided into subtypes. You may have heard of H1N1 or H3N2 – those ...
A subtype of bird flu caused by avian influenza A (H5) virus has been spreading worldwide in wild birds with a few outbreaks in poultry, dairy cows and other mammals across the United States ...