Pulau Jerejak is a smaller island lying off the south-eastern corner of the main island of Penang. It was said to have been inhabited by fisher folk from the maniland state of Kedah long before the British Settlement of Penang was established in 1786.

The original buildings on Pulau Jerejak became known as Camps A and B or later Camps 1 and 2, when other "Camps" 3, 4, and 5 were also constructed in other parts of the island. There were quarters for the medical, administrative and other subordinate staff, as well. Other wards were also added in the course of the years, some by the Kedah State government for its patients.

From the time when Pulau Jerejak segregation centre began operating as a general segregation centre for the Singapore Straits, most male patients from Singapore and the other Straits Settlements territories were sent to Pulau Jerejak, while Singapore only operated collecting centres.

Textual and historical references to this asylum