Plague Ship by Clive Cussler

Captained by the rakish, one-legged Juan Cabrillo and manned by a crew of former military and spy personnel, the Oregon is a private enterprise, available for any government agency that can afford it. They've just completed a top secret mission against Iran in the Persian Gulf when they come across a cruise ship adrift at sea. Hundreds of bodies litter its deck, and, as Cabrillo tries to determine what happened, explosions rack the length of the ship. Barely able to escape with his own life and that of the liner’s sole survivor, Cabrillo finds himself plunged into a mystery as intricate – and as perilous – as any he has ever known and pitted against a cult with monstrously lethal plans for the human race . . . plans he may already be too late to stop