Recent outbreaks of norovirus and Legionnaires’ disease on cruise ships over the past 12 months have reinforced the importance of effective water system management, with CM Technologies (CMT) urging operators to align with updated CDC sanitation rules and adopt the same condition-monitoring discipline used in fuel management.
The US Centers for Disease Control and Prevention (CDC) updated its Vessel Sanitation Programme standards in Nov 2025, marking a significant shift in cruise ship public health. For the first time, all vessels calling at US ports are required to monitor for Legionella.
“The revision represents a strengthening of environmental surveillance obligations,” said Uwe Krüger, joint managing director of CMT, a specialist in marine condition monitoring and onboard testing equipment.
“This is a major regulatory shift, moving the focus beyond acute gastroenteritis caused by norovirus towards structured environmental pathogen control and auditable, data-driven performance verification. The revised standards significantly tighten expectations around potable water system integrity.”
All cruise ships calling at US ports with 13 passengers or more must now carry out documented risk assessments covering potable and recreational water systems, define monitoring frequencies, implement clear remediation protocols where issues are detected, and maintain verifiable records of corrective action.
The ruling follows several recent incidents meeting the CDC’s reporting threshold of 3% or more of passengers reporting gastrointestinal symptoms during a voyage. Over the past year, multiple vessels have reported norovirus outbreaks, while cases of Legionnaires’ disease have also been identified among passengers travelling on two cruise ships.
“While gastrointestinal outbreaks are typically driven by person-to-person transmission, the Legionella cases highlight the importance of maintaining strict temperature control, disinfectant management and circulation stability within potable and recreational water systems,” Krüger added.
David Fuhlbrügger, joint managing director of CMT, further noted: “Pools, spa areas and whirlpools can be breeding grounds, but it is not enough to measure chlorine levels and assume the water is safe. Operators must demonstrate that disinfectant residuals are maintained within defined limits. Filtration performance and overall system effectiveness must also be verified through structured cleaning, monitoring and documentation.”
He added that showers are often overlooked despite presenting a specific risk. “Legionella transmission occurs through inhalation of aerosolised warm water. In many cases, operators sanitise systems after a positive test result but fail to remove limescale from shower heads. Limescale can harbour bacteria, allowing recolonisation. Effective control requires both chemical sanitisation and physical maintenance.”
To support compliance with enhanced monitoring requirements, CMT offers portable potable water testing kits capable of measuring chlorine residuals and dosing, as well as indicators for coliforms, enterococci and other bacteria. Dedicated Legionella testing kits are also available to support structured surveillance programmes, enabling onboard verification rather than relying solely on periodic laboratory analysis.
“In today’s regulatory environment, the ability to demonstrate system performance is just as important as achieving it,” said Fuhlbrügger.
The CDC requirements will be enforced through port inspections, documentation reviews, sampling and outbreak investigations.
All images courtesy of CMT.
