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Requirements for Pandemic Influenz
| A pandemic strain must be… | H5N1 strains… |
|---|---|
| … antigenically novel | … have an H5 HA to which humans |
| have no pre-existing immunity | |
| … virulent enough to cause severe | …have killed ~60% of all humans |
| disease and some mortality | proven to be infected |
| …able to transmit easily from | …have shown only limited |
| human to human | transmission by close contact |
