Caldea IV was a Class M planet in the Caldean system, near the edge of the Typhon Expanse and distant from the United Federation of Planets. The Federation had a colony on the planet's surface. A supply station also orbited the planet. The colony's leader in 2372 was named Marquez.
At some time between the colony's creation and 2372, a Starfleet starship visited the colony. A Starfleet officer became infected with Caldean Acute Cardiopulmonary Syndrome (CACS), an untreatable condition, and inadvertently spread CACS to the colonists. On attempt to beam the officer aboard the ship, the transporter's biofilters rejected the signal, and an emergency system diverted him to the orbiting supply depot. He and a vast majority of the infected colonists died within a twelve-week period after infection.
In 2372, the USS Cantabrian crew responded to a distress call to assist the colony in a medical emergency. Once there, Noah Wrightson was infected with a CACS variant and was isolated aboard the same supply depot. Drs. Marie and Helena Bourget were successful in finding a treatment for this CACS variant, and no colonists were infected with CACS. (Star Trek: The Cantabrian Expeditions: "Isolation")