What is a novel influenza?

Novel influenza describes an influenza A virus subtype or virus strain that has not previously circulated among humans, and to which most people do not have immunity. Novel influenza outbreaks are often caused by the emergence or re-emergence of a new strain of avian or swine influenza virus. Transmission of the virus to humans can occur through contact with infected wild animals or domesticated animals, or through human to human transmission.

To be classified as a novel influenza, the virus must meet several criteria:

- No prior or limited human circulation: The virus must not have been previously recognized in the past 12-24 months, or it may be a virus that is already in circulation but is experiencing a significant antigenic shift.

- Ability to cause widespread infections in humans: The virus must be able to efficiently transmit between humans, establishing and sustaining human-to-human transmission of the virus.

- Pandemic potential: The virus has the potential to cause a pandemic, characterized by widespread and rapid spread of the virus across countries or regions, potentially affecting a large portion of the population.

Novel influenza viruses are often more virulent and can cause more severe disease compared to seasonal influenza viruses. They can pose a significant threat to public health, as populations have little or no pre-existing immunity against them. As a result, novel influenza outbreaks require close monitoring and rapid response from public health authorities, including vaccine development and implementation of infection prevention and control measures, such as antiviral treatments and social distancing.