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What is At present following types of influenza viruses are circulating in the world, except- and explain in detail?
At present three types of influenza viruses are circulating in the world : A (H1N1), A (H3N2) and B virus. WHO global surveillance activities have identified human infection with a new influenza viruse called A (H5N1) in Hong Kong in mid 1997. However, the possibility that the outbreak heralded a global influenza pandemics did not materialize. Ref: PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE , 23rd edition , Page :153