Researchers call for better air flow in cruise-ship dining areas to help prevent disease outbreaks

Diamond Princess cruise ship

junce / iStock

In Science of the Total Environment, a University of Surrey–led research team that measured indoor air quality (IAQ) on board a large cruise ship in August 2023 identifies crowded dining areas as priorities for improved air circulation and the prevention of disease outbreaks.

The investigators, working on the European Union's (EU's) HEALTHY SAILING project, monitored 24-hour indoor carbon dioxide (CO2) levels to evaluate temperature, humidity, ventilation, airborne infection risk, and energy efficiency by monitoring IAQ in three cabins and the buffet, gym, bar, restaurant, pub, and theater of a 5,000-passenger cruise ship traveling between UK and EU ports.

Airborne infection risk was calculated based on the assumption that the air contains doses of virus and that occupants are infected by inhaling a single dose. "The infected person breathes out virus-laden particles at a constant rate, and the infectious dose of the virus can be removed when it decays, falls onto a surface, or is diluted by ventilation," the study authors wrote.

'Hotspots for super-spreading events'

To illustrate disease risk on board cruise ships, the researchers noted the outbreak on the Diamond Princess cruise ship early in the COVID-19 pandemic. The ship was placed under quarantine at Yokohama in Japan for nearly a month, with quarantine of passengers and crew members except to perform essential tasks. The outbreak killed 13 people and resulted in 712 infections.

"The COVID-19 pandemic brought unprecedented challenges to the cruise industry, with passenger ships often labelled 'hotspots' for super-spreading events," corresponding author and Prashant Kumar, PhD, MTech, founding director of the University of Surrey's Global Centre for Clean Air Research (GCARE), said in a university news release

"While significant progress has been made with indoor air quality management across the sector, there remains a clear need for targeted ventilation strategies in high-occupancy areas and energy optimisation in over-ventilated spaces," he added.

A roadmap for cruise operators

In general, IAQ was good (less than 1,000 parts per million [ppm]), with CO2 ranging from 400 to 1,200 ppm. The estimated air change and ventilation rates implied that most ship areas were sufficiently ventilated. Using CO2 levels as a proxy for exhaled breath, the researchers estimated that the likelihood of airborne-disease transmission under normal speaking conditions was under 3%, mainly due to sufficient ventilation relative to occupancy in most areas. 

The insights from this study will serve as a valuable guide for cruise operators, many of whom have firsthand experience with the challenges of viral transmission. 

Ho Yin Wickson Cheung

But in crowded areas in which people raise their voices to be heard (ie, the pub and restaurant), CO2 levels were high (greater than 2,000 ppm), suggesting a risk of disease transmission and the need for better ventilation. In contrast, low temperatures (22.3°C [72.1°F]) and relative humidity levels (68.2%) in cabins and the theater implied over–air conditioning, suggesting energy inefficiency.

Elevated CO2 levels in berths and dining areas reflected the effects of pollution from marine traffic and port operations. While the ship maintained stable air-conditioning levels during docking, the ventilation systems couldn't eliminate the pollution from coming indoors, showing the need for improved air filtration and adaptive ventilation at sea and in port.

Lead author and GCARE PhD student Ho Yin Wickson Cheung said, "The insights from this study will serve as a valuable guide for cruise operators, many of whom have firsthand experience with the challenges of viral transmission. These simple measures, backed by science, provide practical solutions to help ensure the wellbeing of everyone onboard."

This week's top reads

Our underwriters