Overview of the Phase 3 surveillance strategy
Alert system
The alert system is a mechanism to detect and report alerts to those responsible for surveillance. An alert is
a condition that meets a very broad (sensitive) definition that aims to identify all signals that could potentially
be an EVD case or death (or other conditions). Alerts can be generated by the community, at healthfacilities,
or picked-up in the media. Alerts are reported to those in charge of surveillance through various
means, including, but not restricted to, a telephone hotline, texting, emails, etc. Alerts go through a screening
and verification process until they are eventually tested for EVD. The alert system underpins various
approaches to surveillance and must be closely tied to the response.
The systems and processes currently in place in the 3 countries have been designed and implemented
largely to respond to the EVD outbreak. These EVD alert systems must be now expanded to cover the other
diseases and conditions requested by the IDSR.
Live alerts and suspect cases (See figure 1)
Identification
Live alerts or suspect cases can be identified through several mechanisms:
• the community itself identifies an alert (community-based surveillance)
• the patient seeks health care, is identified as an alert or suspect case and is reported (health-facility
based surveillance and routine reporting, including immediate notification and zero reporting)
• surveillance officer actively looks for alerts or suspect cases in health facilities and registers (active case
search in health facilities)
• surveillance officers actively look for alerts or suspect cases in the community through follow-up of
contacts or door-to-door search (active case search in the community)
Community-based and facility-based surveillance are the backbone of surveillance within the IDSR
framework, must be enhanced and pursued indefinitely.
Active case search in the community and health facilities are to complement the above as part of an
investigation of a probable or confirmed case or in places with active transmission chains, and should be
discontinued once there is no more active transmission chain.