Map of Covid-19 spread
Alert color codes
For effective outbreak response, Green, Yellow, Orange and Red Zones can be continually identified and updated 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).
Types of Zones
- Green Zones: Regions without confirmed cases or with a few infected travelers arriving from other regions
- Yellow Zones: Regions with a few cases of local transmission, but without clusters of community transmission
- Orange Zones: Regions adjacent to Red Zones or with small clusters
- Red Zones: Regions that have sustained community transmission
| Response Protocol | Green | Yellow | Orange | Red |
|---|---|---|---|---|
| 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 travelling 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) | ✓ | ✓ | ✓ | ✓ |
| Enforce 14 day quarantine for individuals who are likely to have had contact with infected individuals, including all travellers from Red 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 non-essential gatherings, especially in confined spaces | ✓ | ✓ | ✓ | |
| Provide maximum protection for medical staff | ✓ | ✓ | ✓ | |
| Promote personal protection including facial masks | ✓ | ✓ | ||
| Postpone/cancel non-essential gatherings and events | ✓ | ✓ | ||
| Disinfect public places | ✓ | ✓ | ||
| Actively test everyone with symptoms | ✓ | ✓ | ||
| Increase test capacity and speed | ✓ | ✓ | ||
| Suspend schools, places of worship and businesses | ✓ | |||
| Restrict travel only for essential purposes | ✓ | |||
| Lock-down (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 | ✓ |
This color-coded zone-based scheme is based on the idea that in areas in which the virus is spreading within the community, the social connectivity must be lowered to the point where each individual infected will infect less than one other person on average. This decreased social connectivity will result in an exponential decrease in the number of new cases (although, due to the incubation period, there may be a time-delay before this is observed).
Travel restrictions/reduction allow for the more extreme social distancing measures (e.g. those in orange and red zones) to be implemented only in places currently experiencing significant local transmission rather than everywhere in the world at once.
For areas with only imported cases or a very small amount of local transmission (green and yellow zones), contact tracing may be sufficient to prevent the outbreak from growing, and thus the main goal is to avoid large social gatherings that allow for ‘super-spreader’ events. But if it becomes clear that the outbreak has not been contained to just a few cases (in which case it is very likely that there are additional unknown infected individuals), the number of new infections will continue to exponentially increase unless the measures for orange or red zones are immediately implemented.
The goal of both red and orange zone restrictions is to reduce general social connectivity to the point where there is an exponential decrease in the number of cases over time. In red zones, due to the higher numbers of cases (and therefore also the increased chances of exporting a case), stricter social distancing measures and travel restrictions are recommended.
For more information on medical and social responses, see:
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