H7N9 is the designation for one subtype of influenza viruses that is sometimes found in birds, but does not normally infect humans. Like all influenza-A viruses, there are also different strains of H7N9. Beginning at the end of March 2013, China reported human and bird (poultry) infections with a new strain of H7N9 that is very different from previously seen H7N9 viruses. Note how this image diagrams the recombination of genes, which takes place leading to the creation of this new strain of the H7N9 influenza virus.