Influenza A (H2N2) virus
H2N2 is a subtype of the type influenzavirus A. H2N2 has mutated into various strains including the Asian flu strain (now extinct in the wild), H3N2, and various strains found in birds. It is also suspected of causing a human pandemic in 1889. The geographic spreading of the 1889 Russian flu have been studied and published.
Notable H2N2 Incidents and Outbreaks
Russian flu (1889 - 1890)
Some believe that the 1889 - 1890 Russian flu was caused by the influenzavirus A virus subtype H2N2, but the evidence is not conclusive. It is the earliest flu pandemic for which detailed records are available. "The 1889 pandemic, known as the Russian Flu, began in Russia and spread rapidly throughout Europe. It reached North America in December 1889 and spread to Latin America and Asia in February 1890. About 1 million people died in this pandemic.
Asian flu (1957-1958)
The "Asian Flu" was a category 2 flu pandemic outbreak of influenzavirus A that originated in China in early 1956 lasting until 1958. Some authors believe it originated from mutation in wild ducks combining with a pre-existing human strain. The virus was first identified in Guizhou. It spread to Singapore in February 1957, reached Hong Kong by April, and US by June. Death toll in the US was approximately 69,800. Estimates of worldwide deaths caused by this pandemic varies widely depending on source; ranging from 1 million to 4 million, with WHO settling on "about 2 million". Asian Flu was of the H2N2 subtype (a notation that refers to the configuration of the hemagglutinin and neuraminidase proteins in the virus) of type A influenza, and an influenza vaccine was developed in 1957 to contain its outbreak.