Background: Per the US Core specification Each CareTeam must have: a patient a participant role for each careteam members names of careteam members which can be: a practitioner or practitioner type (doctor, nurse, therapist)* the patient a relative or friend or guardian an organization *See the next section for how practitioner members are represented in this Profile. Each Condition must support: a status code   Reasoning: US Core is purposefully silent on the period element because it was not considered to   sets minimum expectations for the  CareTeam  resource for identifying the Care Team members associated with a patient .   The status of "active" is determined by the individual business rules imposed by the systems.  Implementers using US Core and implementation guides derived from US Core may further constrain the CareTeam Profile and provide further guidance to specify the relationship be the status and the period.  Suggestion: Feel free to submit a Jira issue to update the FHIR Core specification and provide your comments/feedback directly there.