TY - JOUR AU - Ellis, Joanna S. AU - Alvarez-Aguero, Adriana AU - Gregory, Vicky AU - Lin, Yi Pu AU - Hay, A. AU - Zambon, Maria C. T1 - Influenza AH1N2 Viruses, United Kingdom, 2001–02 Influenza Season T2 - Emerging Infectious Disease journal PY - 2003 VL - 9 IS - 3 SP - 304 SN - 1080-6059 AB - During the winter of 2001–02, influenza AH1N2 viruses were detected for the first time in humans in the U.K. The H1N2 viruses co-circulated with H3N2 viruses and a very small number of H1N1 viruses and were isolated in the community and hospitalized patients, predominantly from children <15 years of age. Characterization of H1N2 viruses indicated that they were antigenically and genetically homogeneous, deriving the hemagglutinin (HA) gene from recently circulating A/New Caledonia/20/99-like H1N1 viruses, whereas the other seven genes originated from recently circulating H3N2 viruses. Retrospective reverse transcription-polymerase chain reaction analysis of influenza A H1 viruses isolated in the U.K. during the previous winter identified a single H1N2 virus, isolated in March 2001, indicating that H1N2 viruses did not widely circulate in the U.K. before September 2001. The reassortment event is estimated to have occurred between 1999 and early 2001, and the emergence of H1N2 viruses in humans reinforces the need for frequent surveillance of circulating viruses. KW - influenza KW - H1N2 KW - reassortment KW - evolution KW - surveillance KW - diagnosis KW - research KW - United Kingdom DO - 10.3201/eid0903.020404 UR - https://wwwnc.cdc.gov/eid/article/9/3/02-0404_article ER - End of Reference