The effective reproductive number (Reff) of different locations

The change in effective reproduction number (Reff) from the early and late phase of the virus.

The early-phase of the virus (ie. the "before") approximately corresponds to less strict public health measures in most locations (ie. alert levels 1 and 2). The late-phase of the virus approximately corresponds to stricter public health measures in most locations (ie. alert levels 3 and 4).

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A value of Reff > 1 means an outbreak is likely (the larger the value, the faster the increase in the number of infections). A sustained value of Reff < 1 means the virus will be eliminated from the community.

The alert levels correspond to interventions equivalent to (but not perfectly aligned with) New Zealand’s alert levels 1 to 4. The levels are: level 1 – prepare, level 2 – reduce, level 3 – restrict, and level 4 – eliminate.