Table 1 Definitions used for dates of interest in the outbreak timeline

Onset

For diseases of which one case constitutes a potential outbreak, the date of onset of symptoms of the primary case.

For diseases that are normally endemic but are considered epidemic when an unusual increase in burden is observed, the date on which the outbreak threshold was crossed, according to the authors.

If investigation revealed previous undetected outbreaks of the same health event, this was also noted.

Detection

The date a report of a possible outbreak was sent to the highest appropriate level of authority. This could be the date of initial detection, if no authorities were required to be notified.

Confirmation

The date on which the aetiologic agent of the outbreak was confirmed.

Investigation

The date an investigation team arrived to the outbreak-affected community.

Declaration

The date the outbreak was officially declared as such by health authorities of the country concerned.

Control

The first day of a reactive vaccination campaign (we only computed the date of this event for diseases for which vaccination was the main control intervention available, since the date of implementation of other control interventions, such as water and sanitation, is difficult to define).