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Quarantine flag

Posted to Maritime Musings (by on July 13, 2020

A visible warning to stay clear.

  • Quebec
  • Lima

By Dennis Bryant and Rob Murray

There is no signal in the International Code of Signals for ‘quarantine’ (indeed the word ‘quarantine’ does not appear in the code). Today ships signal either ‘ My vessel is “healthy” and I request free pratique’ with a single Q (Quebec) flag or ‘I require health clearance’ with the double signal QQ (Quebec Quebec). Either is correct for a vessel yet to be cleared for pratique (pratique is permission to do business at a port, granted to a ship that has met quarantine or other health regulations). The Q (Quebec) flag is square in shape and pure yellow. Continuing to fly either of these signals indicates a vessel is yet to receive clearance (and is thus effectively in quarantine). Once the local authorities have determined that the ship’s health problems have been resolved and removed a quarantine order, the ship may strike the signal and raise the national ensign for the port they are entering.

In years gone by, editions of the International Code of Signals (ICOS) did contain signals for vessels that suspected they harbored, or could be harboring, contagious diseases. In Brown’s 1916 edition the L (Lima) flag (black and yellow squares) signified ‘I have or had some dangerous, infectious disease on board.’ And this meaning was continued in the 1923 and 1931 editions. When the ICOS was radically overhauled in 1965 to recognize the then-widespread use of radio communications (relatively rare when the earlier editions were published) the ICOS shrank from a nearly 600 page tome to a comparatively svelte 160 pages, and the meaning of the L (Lima) flag was simplified to mean only ‘You should stop your vessel instantly’ to eliminate any possible confusion. This meaning has persisted through current versions. Mariners can find a copy of the current (1969, revised 2003) edition of the ICOS for free download here.

In an interesting nod to past practice, some local ordinances were enacted to re-use the old meaning of the Lima flag for the 2020 COVID-19 pandemic, notably in Alaska and Newport, R.I.

The concept of quarantine is ancient and is mentioned in the Old Testament. The term itself is derived from the practice of the city-state of Venice during the Middle Ages of requiring ships arriving from locations known to being experiencing diseases such as the plague to anchor or moor off the port for 40 days (quaranta giorni) so that any disease on board might run its course. The practice of quarantine has varied over the centuries, but the concept of protecting the public health by restricting the movements of individuals who are suspected of possibly harboring serious disease has remained constant.

The World Health Organization (WHO) provides guidelines on how and when quarantine should be used, but its actual implementation is left to the discretion of individual nations. In the United States, the Center for Disease Control and Prevention (CDC) administers the federal quarantine program, but the separate states and local communities also have broad powers. Ships arriving in a US port with serious disease on board are required to provide advance notification. The ship may be required to undertake certain sanitary measures and to exercise various controls over all persons on board to prevent them from serving as disease vectors potentially infecting the local populace. The closest we have come recently (pre-COVID-19) to a general quarantine affecting the maritime industry was during the 2002 SARS epidemic, which heavily impacted southeast Asia. The COVID-19 pandemic, declared March 11 2020 was the first to have truly widespread impact. A future pandemic, whether the result of avian flu or otherwise, may see widespread implementation of quarantine measures.

(This article was originally published on January 6, 2012, but was updated on July 13, 2020)