After several days at sea, the Celebrity Mercury seems finally free of a stomach bug that afflicted nearly 1,000 passengers on its previous three voyages from Charleston.

This most recent Caribbean-bound cruise departed a day late, following an intensive, three-day cleaning. The U.S. Centers for Disease Control and Prevention had issued a "no-sail recommendation" after the third consecutive outbreak of suspected norovirus.

CDC spokesman Ricardo Beato said investigators with his agency inspected the ship Sunday with the option of extending the disinfection another day. The agency is awaiting test results of samples it sent to a laboratory to identify the illness conclusively as norovirus.

Norovirus symptoms include nausea, vomiting, diarrhea and stomach cramps, sometimes accompanied by a low-grade fever. The highly contagious illness usually lasts a day or two and spreads through food, water or person-to-person contact.

Norovirus generally affects confined communities, such as cruise ships, schools and hospitals. The state Department of Health and Environmental Control has investigated twice the usual number of gastrointestinal illness clusters across South Carolina this year.

Celebrity brought an extra 50 crew members to help sanitize the ship, according to Cynthia Martinez, corporate communications manager for parent company Royal Caribbean Cruises.

She said Celebrity contracted with one company to steam-clean the carpet in all state rooms and public areas and with another company to bring 12 technicians onboard with electrostatic sprayers that use a charge to evenly distribute cleaning solutions.

Celebrity let passengers on the current sailing cancel their trips and claim a full refund, plus a future cruise certificate equal to 15 percent of their fares. Each person who opted to sail Sunday received an onboard credit for two days of his or her fare, according to Martinez, plus a future cruise certificate for 25 percent of the fare.

Although the ship can carry 1,886 passengers, 1,076 people sailed out Sunday, according to Martinez.

She said the next cruise, which departs Monday after the current voyage returns, brings the ship back to its original schedule. The Mercury kicked off the Port of Charleston's 2010 cruise season Feb. 15.