Influenza A virus subtype H2N2 (A/H2N2) is a subtype of '' Influenza A virus''. H2N2 has mutated into various strains including the " Asian flu" strain (now extinct in the wild),

H3N2 Influenza A virus subtype H3N2 (A/H3N2) is a subtype of viruses that causes influenza (flu). H3N2 viruses can infect birds and mammals. In birds, humans, and pigs, the virus has mutated into many strains. In years in which H3N2 is the predomina ...

, and various strains found in

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s. It is also suspected of causing a human pandemic in 1889. The geographic spreading of the 1889 Russian flu has been studied and published.

Russian flu

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 An influenza pandemic is an epidemic of an influenza virus that spreads across a large region (either multiple continents or worldwide) and infects a large proportion of the population. There have been six major influenza epidemics in the las ...

for which detailed records are available. More recently, there are speculations that it might have been caused by one of the coronaviruses first discovered in the 1960s.

Asian flu

The "Asian Flu" was a category 2

outbreak of

influenzavirus A '' A virus'' (''IAV'') causes influenza in birds and some mammals, and is the only species of the genus ''Alphainfluenzavirus'' of the virus family ''Orthomyxoviridae''. Strains of all subtypes of influenza A virus have been isolated from wild ...

that originated in Singapore in early 1957 lasting until 1958. The first cases were reported in Singapore in February 1957. In February 1957, a new influenza A (H2N2) virus emerged in East Asia, triggering a pandemic (“Asian Flu”). This H2N2 virus was composed of three different genes from an H2N2 virus that originated from an avian influenza A virus, including the H2 hemagglutinin and the N2 neuraminidase genes. It was first reported in Singapore in February 1957, Hong Kong in April 1957, and in coastal cities in the United States in summer 1957. Some authors believe it originated from mutation in wild ducks combining with a pre-existing human strain. Other authors are less certain. It reached

Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delta i ...

by April, and US by June. Estimates of US and worldwide deaths caused by this pandemic varies widely depending on source; ranging from approximately 69,800 to 116,000 in the United States, and worldwide from 1 million to 4 million, with the

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...

(WHO) settling on "about 2 million," with an overall mortality rate of 0.6%. Asian Flu was of the H2N2 subtype (a notation that refers to the configuration of the

hemagglutinin In molecular biology, hemagglutinins (or ''haemagglutinin'' in British English) (from the Greek , 'blood' + Latin , 'glue') are receptor-binding membrane fusion glycoproteins produced by viruses in the '' Paramyxoviridae'' family. Hemagglutinins a ...

and

neuraminidase Exo-α-sialidase (EC 3.2.1.18, sialidase, neuraminidase; systematic name acetylneuraminyl hydrolase) is a glycoside hydrolase that cleaves the glycosidic linkages of neuraminic acids: : Hydrolysis of α-(2→3)-, α-(2→6)-, α-(2→8)- glyc ...

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

s in the virus) of type A influenza, and an influenza vaccine was developed in 1957 to contain its outbreak. The Asian Flu strain later evolved via antigenic shift into

which caused a milder pandemic from 1968 to 1969. Both the H2N2 and H3N2 pandemic strains contained avian influenza virus RNA segments. Influenza subtypes

Test kits

From October 2004 to February 2005, approximately 3,700 test kits of the 1957 H2N2 virus were accidentally spread around the world from the

College of American Pathologists The College of American Pathologists (CAP) is a member-based physician organization founded in 1946 comprising approximately 18,000 board-certified pathologists. It serves patients, pathologists, and the public by fostering and advocating ...

(CAP). CAP assists laboratories in accuracy by providing unidentified samples of

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsk ...

es; private contractor Meridian Bioscience in

Cincinnati Cincinnati ( ) is a city in the U.S. state of Ohio and the county seat of Hamilton County. Settled in 1788, the city is located at the northern side of the confluence of the Licking and Ohio rivers, the latter of which marks the state line wit ...

U.S. The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, chose the 1957 strain instead of one of the less deadly

avian influenza virus Avian influenza, known informally as avian flu or bird flu, is a variety of influenza caused by viruses adapted to birds.Pandemic preparedness: lessons learnt from H2N2 and H9N2 candidate vaccines
*
New Scientist: Bird Flu

Pandemic-causing 'Asian flu' accidentally released

Persistence of Q strain of H2N2 influenza virus in avian species: antigenic, biological and genetic analysis of avian and human H2N2 viruses

External links

Influenza Research Database
Database of influenza sequences and related information. {{DEFAULTSORT:Influenza A Virus Subtype H2n2 H2N2 1957 in Hong Kong 1889–1890 flu pandemic de:Asiatische Grippe es:Gripe asiática it:Influenza asiatica pt:Gripe asiática sv:Asiaten zh:亚洲流感