The dock landing ship Fort McHenry has apparently been avoiding port calls for months after 25 sailors and Marines aboard were diagnosed with a viral disease in December.

In a statement, U.S. 5th Fleet confirmed that the service members, including sailors deployed on the ship and members of the 22nd Marine Expeditionary Unit, were diagnosed with parotitis, a disease similar to mumps. CNN was first to report the outbreak Wednesday.

According to the Centers for Disease Control, the disease involves swelling of one or both salivary glands. CDC literature indicates infections may be on the rise, with several hundred reported cases of acute parotitis during the 2014-2015 flu season in the U.S., the largest number of reported cases in history.

The first case was detected Dec. 22, officials said, and affected service members were quarantined and treated while they displayed symptoms. To date, 24 of the 25 have returned to duty, according to a statement, and there have been no active cases since March 9.

Fifth Fleet officials said none of the cases was life-threatening and full recoveries are expected in all cases. To minimize the spread of the disease, all living and working spaces affected were cleaned and disinfected, and the entire population aboard Fort McHenry received measles, mumps and rubella booster vaccinations.

"Fort McHenry's operational schedule has been modified while the ship's medical team monitors crew health to ensure the readiness of her Sailors and Marines," officials said. " ... Routine unit-level training and operations have continued."

Officials with 5th Fleet did not immediately respond to questions about specific modifications to the ship's operational schedule, but releases tracking the deployment indicate the Fort McHenry has not made a port stop since early January.

The ship left its homeport in Mayport, Florida, in December for a seven-month deployment with the Kearsarge Amphibious Ready Group and the 22nd MEU to support operations in Europe and the Middle East.

The ship made a scheduled port visit in Constanta, Romania, on Jan. 7, according to military news releases. Following the port stop, the ship spent time in the Mediterranean before moving into the 5th Fleet area of operations in the waters surrounding the Middle East.

The Fort McHenry transited the Suez Canal on Jan. 15.

In addition to multiple replenishments-at-sea and a variety of onboard training evolutions, the troops aboard conducted a passing exercise, or PASSEX, on Feb. 14 with a guided-missile frigate from the Egyptian Navy in the Northern Arabian sea, and a burial-at-sea Feb. 19 for 36 military veterans. The ship transited the Strait of Hormuz, between the Persian Gulf and Gulf of Oman, on March 11.

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at @HopeSeck.