From the 1882 edition of
The international code of signals for the use of all nations American Edition, by United States Navy BUREAU OF NAVIGATION. (
https://archive.org/details/bub_gb_NfwsAAAAYAAJ/mode/2up ):
DKL = Crew ill
DLK = Passenger or passengers ill with infectious complaint
DSO Quarantine. In Quarantine.
DSH Quarantine officers.
DSJ Are you in quarantine?
DSK Do you come from any port putting you in quarantine?
DSL Have you a clean bill of health?
DSM What quarantine shall I get?
DSN Have you had any communication with infected vessels?
DSP Am (or, is) in quarantine (number of days to be indicated.)
DSQ Out of quarantine.
DSR Quarantine at (place indicated) is ___ days for vessels from ___ (place indicated).
DST Pratique*.
DSV Broke the quarantine laws; breaking quarantine laws.
DSW Clean bill of health from ___.
DTB Ships from ___ did not get pratique* at ___ when I left.
DTC You will get quarantine.
DTF When I am out of quarantine.
* pra·tique /praˈtēk/ - noun historical
permission granted to a ship to have dealings with a port, given after quarantine or on showing a clean bill of health.