The COVID-19 outbreak remains at the centre of attention, given that more and more countries report of positively confirmed cases. Thus, the World Health Organization (WHO) issued four transmission scenarios to help people be aware of the situation and know how to deal with the situation.
The table above presents the four transmission scenarios. Accordingly, the four scenarios are:
- Countries with no cases (No Cases);
- Countries with 1 or more cases, imported or locally detected (Sporadic Cases);
- Countries experiencing cases clusters in time, geographic location and/or common exposure (Clusters of cases);
- Countries experiencing larger outbreaks of local transmission (Community transmission).
Countries could experience one or more of these scenarios at the sub-national level and should adjust and tailor their approach to the local context.
#1 Transmission scenario: No reported cases
Aim: Stop transmission and prevent spread.
Priority areas of work: Activate emergency response mechanisms
Risk communication and public engagement: Educate and actively communicate with the public through risk communication and community engagement
Case finding, contact tracing and management: Conduct active case finding, contact tracing and monitoring; quarantine of contacts and isolation of cases
Surveillance: Consider testing for COVID-19 using existing respiratory disease surveillance systems and hospital-based surveillance.
Public health measures: Hand hygiene, respiratory etiquette, practice social distancing.
Laboratory testing: Test suspect cases per WHO case definition, contacts of confirmed cases; test patients identified through respiratory disease surveillance
Case management Prepare to treat patients, Ready hospitals for potential surge and Promote self-initiated isolation of people with mild respiratory symptoms to reduce the burden on health systems
IPC: Train staff in IPC and clinical management specifically for COVID-19 / Prepare for surge in health care facility needs, including respiratory support and PPE
Societal response: Develop all-of-society and business continuity plans
#2 Transmission scenario: One or more cases, imported or locally acquired
Aim: Stop transmission and prevent spread.
Priority areas of work: Enhance emergency response mechanisms
Risk communication and public engagement: Educate and actively communicate with the public through risk communication and community engagement
Case finding, contact tracing and management: Enhance active case finding, contact tracing and monitoring; quarantine of contacts and isolation of cases
Surveillance: Implement testing for COVID-19 using existing respiratory disease surveillance systems and hospital-based surveillance.
Public health measures: Hand hygiene, respiratory etiquette, practice social distancing.
Laboratory testing: Test suspect cases per WHO case definition, contacts of confirmed cases; test patients identified through respiratory disease surveillance
Case management: Treat patients and ready hospitals for surge; develop triage procedures
Promote self-initiated isolation of people with mild respiratory symptoms to reduce the burden on health system
IPC: Train staff in IPC and clinical management specifically for COVID19 / Prepare for surge in health care facility needs, including respiratory support and PP
Societal response: Implement all-of-society, repurpose government and ready business continuity plan
#3 Transmission scenario: Most cases of local transmission linked to chains of transmission
Aim: Stop transmission and prevent spread.
Priority areas of work: Scale up emergency response mechanisms
Risk communication and public engagement: Educate and actively communicate with the public through risk communication and community engagement
Case finding, contact tracing and management: Intensify active case finding, contact tracing and monitoring; quarantine of contacts and isolation of cases
Surveillance: Expand testing for COVID-19 using existing respiratory disease surveillance systems and hospital-based surveillance.
Public health measures: Hand hygiene, respiratory etiquette, practice social distancing.
Laboratory testing: Test suspect cases per WHO case definition, contacts of confirmed cases; test patients identified through respiratory disease surveillance
Case management: Treat patients and ready hospitals for surge; enhance triage procedures; activate surge plans for health facilities
Activate surge plans for health facilities (designate referral hospitals, defer elective procedures)
IPC: Train staff in IPC and clinical management specifically for COVID-19 / Advocate for home care for mild cases, if health care systems are overwhelmed, and identify referral systems for high risk groups
Societal response: Implement all-of-society resilience, repurpose government, business continuity, and community services plans
#4 Transmission scenario: Outbreaks with the inability to relate confirmed cases through chains of transmission for a large number of cases, or by increasing positive tests through sentinel samples (routine systematic testing of respiratory samples from established laboratories
Aim: Slow transmission, reduce case numbers and end community outbreaks.
Priority areas of work: Scale up emergency response mechanisms
Risk communication and public engagement: Educate and actively communicate with the public through risk communication and community engagement / Continue contact tracing where possible, especially in newly infected areas, quarantine of contacts, & isolation of cases; apply self-initiated isolation for symptomatic individuals
Surveillance: Adapt existing surveillance systems to monitor disease activity (e.g. through sentinel sites)
Public health measures: Hand hygiene, respiratory etiquette, practice social distancing.
Laboratory testing: Test suspect cases per WHO case : Test suspect cases per WHO case definition and symptomatic contacts of probable/confirmed cases; test patients identified through respiratory disease surveillance. If testing capacity is overwhelmed prioritize testing in health care settings and vulnerable groups. In closed settings test only the first symptomatic suspect cases.
Case management: Prioritize care and activate triage procedures. Scale up surge plans for health facilities (designate referral hospitals, defer elective procedures) / Implement self-initiated isolation of people with mild respiratory symptoms to reduce the burden on health systems
IPC: Retrain staff in IPC and clinical management specifically for COVID-19/ Implement health facilities surge plans
Societal response: Implement all-of-society resilience, repurpose government, business continuity, and community services plans
