Influenza H3N2 — United States
According to the International Health Regulations (IHR), human infection caused by a novel influenza A virus subtype is an event that has the potential for high public health impact. A novel influenza A virus is considered to have the potential to cause a pandemic if:
(1) the virus has demonstrated the capacity to infect and transmit efficiently among humans; and
(2) differs from currently-circulating seasonal human influenza viruses such that the hemagglutinin (HA) gene (or protein) is
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