This is the CodeSystem that contains all the codes in US Public Health Usage Context (http://hl7.org/fhir/us/ecr/CodeSystem/us-ph-usage-context) and US Public Health Usage Context (http://hl7.org/fhir/us/ecr/CodeSystem/us-ph-usage-context). E.g. what you have to deal with if you get resources containing codes in either of them
Generated Narrative: CodeSystem 53cc55e8-dbef-45a8-8e72-fd29f2324ee1-23
This code system http://hl7.org/fhir/comparison/CodeSystem/53cc55e8-dbef-45a8-8e72-fd29f2324ee1-23
defines codes, but no codes are represented here