This is the ValueSet that contains all the codes in ActClassTransmissionExposure (http://terminology.hl7.org/ValueSet/v3-ActClassTransmissionExposure) and ActClassTransmissionExposure (http://terminology.hl7.org/ValueSet/v3-ActClassTransmissionExposure). E.g. what you have to deal with if you get resources containing codes in either of them