Phases of COVID-19

Characteristics

Contact tracing

Phase 0: No Case

No reported cases in country/ Region/ Zone/ Districts

Aim: Preparedness

Sensitize the population to the idea of outbreak control measures including contact tracing, quarantine, individual and community social distancing

Phase 1: Early stage of outbreak

One or more imported cases

Limited local transmission related to imported cases

Aim: Prevent sustained transmission

Conduct contact tracing (contact identification for all confirmed cases, contact listing and classification, choose contact follow-up approach and do daily contact follow-up)

Phase 2: Expanding outbreak

Increasing number of imported cases

Increased local spread but all cases linked to known transmission chains

Outbreak clusters with a known common exposure

Aim: Contain and slow transmission

Intensify contact tracing and adherence to quarantine as much as possible.

If resources reach limit, priorities contacts follow-up with the highest risk exposures, particularly health workers and vulnerable populations

Phase 3: Early stage of outbreak

One or more imported cases

Limited local transmission related to imported cases

Aim: Prevent sustained transmission

Conduct contact tracing (contact identification for all confirmed cases, contact listing and classification, choose contact follow-up approach and do daily contact follow-up)

Phase 4: Large outbreak with nationwide transmission

Widespread sustained community transmission

Multiple generation transmission chains can be identified but most cases occurring outside of chains

Community-wide transmission throughout all or nearly all of the country

Aim: Contain and slow transmission

Intensify contact tracing and adherence to quarantine as much as possible.

If resources reach limit, prioritize contact follow-up with the highest risk exposures, particularly health workers and vulnerable populations