Every ship that carries 13 or more passengers and has a foreign or international itinerary with United States ports is under the jurisdiction of the Vessel Sanitation Program (VSP). This program is monitored by the CDC. These vessels are inspected (unannounced) twice a year, and are subject to reinspection, when necessary.
Inspections focus on:
The ship's water supply (to determine how water is stored, distributed, protected, and disinfected)
The ship's pools and spas (to ensure proper filtration and disinfection)
The ship's food (to determine how food is protected during storage, preparation, and service)
The potential for contamination of food and water (to determine what interventions are needed for surveillance)
The practices and personal hygiene of the ship's staff (to ensure use of appropriate hygienic practices and cleanliness)
The general cleanliness and physical condition of the ship (to ensure cleanliness and the absence of insects and rodents)
The ship's ventilation systems (to ensure appropriate maintenance and cleaning of air handling systems)
The ship's medical facilities (to ensure appropriate gastrointestinal illness surveillance documentation and medical logs)
The ship's hotel accommodations (to evaluate cleaning sequences and procedures for infection control)
The ship's training programs in general environmental and public health practices (to determine the scope and effectiveness of this training)
Ships are given a score based on a 100-point scale. To pass inspection, a ship must score 85 or above. If a ship fails inspection, it will generally be reinspected within 30 to 45 days. However, if the reason for failure poses an imminent public health risk, the VSP may recommend that the ship not sail.
Inspection reports, scores, and additional information can be seen on the VSP website. A report referred to as the "green sheet" can also be viewed on the website, which is a listing of all current inspection scores for active vessels in the program.
Generally, the lower the score, the lower the level of sanitation. However, a low score does not mean passengers will suffer gastrointestinal problems or other illnesses. Ships are required to maintain a standardized gastrointestinal illness report for each cruise, with the number of cases of illnesses by dates of onset and total numbers of passengers and crew members affected.
If at least two percent or more of the passengers and/or crew members have gastrointestinal illness on a given cruise, the VSP may conduct an investigation to determine if an outbreak has occurred.
Given the number of persons who enjoy cruises each year, the rate of gastrointestinal illnesses on cruise ships is very low. There was an increase in the number of norovirus outbreaks in 2006 and 2007. This occurred at the same time as the appearance of two new types of norovirus, which were identified as being responsible for 79 percent of those outbreaks. The CDC reports that it is not clear if the increase in outbreaks is directly related to how these new types of norovirus were spread, to their ability to cause illness, or to another unknown factor.