Isolation is not needed for measles due to -
Transmission directly from person to person by droplet infection from 4 days before onset of rash until 4days thereafter. REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 21ST EDITION. PAGE NO - 147
There are healthy carriers
Carriers are convalascents
The infectivity in diseased is low
There are incubatory carriers
Communicable diseases