Chen Shen and Yaneer Bar-Yam

For effective outbreak response identify Green, Yellow, Orange and Red Zones dynamically to help monitor the situation, to increase response effort where needed, and to release areas from constraints when possible. Individual Yellow, Orange and Red Zones should be as small as practical (neighborhoods, urban areas, counties/precincts, states) so that borders, checkpoints and travel restrictions are established to other even equal color zones.

GREEN ZONES: Countries or localities without confirmed cases or with a few infected travelers arriving from other countries

• Raise public awareness, including disease transmission mechanisms and avoidance (social distancing, hand washing, masks).

• Develop rapid response process to test domestic citizens for related symptoms.

• Perform quick tests at borders of individuals traveling from Yellow or Orange Zones to identify symptomatic individuals (fever, cough). Passengers entering from the same vehicle (airplane, train, bus, car) should be detained for the result. If positive, enforce 14 day quarantine of the confirmed case, and of other passengers and crew (individually or in small groups). Inform the region of origin for corresponding actions.

• Enforce 14 day quarantine for at-risk individuals, including all travelers from Red Zones.

YELLOW ZONES: Countries or localities with a few cases of local transmission, but without clusters of community transmission (e.g. Singapore, Germany)

• All the responses of Green Zones

• Identify contacts of confirmed cases (contact tracing), and test, monitor and/or self-isolate them.

• Promote personal protection including social distancing, hand washing, sneeze etiquette.

• Frequently monitor the health condition of a selected group of people with frequent social contact, especially in the area where local transmission is detected, for early case and outbreak detection 

• Urge citizens to avoid nonessential gatherings, especially in confined spaces

• Provide maximum protection for medical staff

ORANGE ZONES: Countries or localities adjacent to Red Zones or with small clusters (e.g. Japan)

• All the responses of Yellow Zones

• Promote personal protection including facial masks

• Postpone/cancel nonessential gatherings and events

• Disinfect public places

• Actively test everyone with symptoms

• Increase test capacity and speed

RED ZONES: Countries or localities that have sustained community transmission (e.g. China, South Korea, Italy)

• All the responses of Orange Zones

• Suspend schools, places of worship and businesses

• Restrict travel only for essential purposes

• Lockdown (quarantine) infected communities keeping people in their homes and delivering necessities to them without contact

• Quarantine contacts of cases

• Galvanize national resources (medical, logistical...) for the quarantined areas

• Separate facilities for infection cases from other health services

• Create different tiers of hospitals to separate and treat cases of different severity

For more information on medical and social response, see:

• WHO Technical Guidance

• Singapore Guidelines