The concepts are similar. All are measures to prevent possible spread of disease. Quarantine refers to separating those exposed to a communicable disease to assess for symptoms. Isolation refers to separating those believed to be infected by a communicable disease until they are no longer communicable. Shelter in place initially referred to taking shelter wherever you are located (for example, your home, a nearby building or business, or even your vehicle) in anticipation of some imminent emergency. See CDC information on sheltering in place here. The “shelter in place” concept has been expanded in the current coronavirus epidemic to include orders from health officials to remain in one’s home unless performing certain “essential activities.” See a sample “shelter in place” order enacted on March 16 in the San Francisco Bay area here.
Health care providers may be put under different types of restrictions including self-monitoring where the provider checks for fever or respiratory symptoms several times each day and reports abnormal findings, self-monitoring with delegated supervision where the healthcare facility at which a provider works checks for fever or symptoms prior to the provider’s shift, and active monitoring where a government health authority regularly checks on a provider to inquire about fever or other symptoms.