Reasons for outbreaks of mass infections on cruise ships

As soon as the COVID-19 had spread in several vessels, the scientific community started to analyze the cases. Here we share some of the findings from the paper "An emergency responding mechanism for cruise epidemic prevention—taking COVID-19 as an example," written by Xiaofei Liu and Yen-Chiang Chang and published in the Marine Policy journal. The paper was submitted in March and published in June 2020. The hyperlink is the following: https://www.sciencedirect.com/science/article/pii/S0308597X20302451

We do not delve into the conclusions since those are very much framed in the Chinese health and safety regulations. Instead, we prefer to focus on the second section of the paper--Reasons for outbreaks of mass infections on cruise ships--since those comments are more relevant for a global discussion that goes farther than the boundaries of the Far East. If some experts from the cruise industry could react to these excerpts, it would be ideal because, in that way, the readers could read the different perspectives about each particular issue and draw their conclusions.

The authors argue that there are five main reasons why cruises are prone to the outbreaks of mass infections. The first one has to do with how airtight structures stagnate internal microclimates. "A cruise ship is a highly airtight place, with its internal cabins being divided into passenger accommodation and public spaces, in addition to the areas required for the various operations of the ship. The internal environment of a cruise ship is narrow with varying cabin spaces. Some cabins, even with large accommodating spaces have no windows for ventilation and have only natural light. Such cabins solely rely on air conditioning to maintain the air quality, which can lead to microclimate stagnation (...) small cabins and the long gathering time in the dining and entertainment rooms led to a high probability of contact infection. Besides, inadequate cabin air replacement would increase the risk of spread by aerosol, so gathering epidemics of respiratory infections are more likely to occur on cruise ships."

The second reason is that central air-conditioning does not help to keep effective quarantines. "The internal ventilation of cruise cabins is mostly regulated by central air-conditioning. The circulation of central air-conditioning is divided into an external circulation system and an internal circulation system (...) Although air-conditioning has an air filter, it is ineffective in removing COVID-19; thus, the internal circulation system of central air-conditioning can neither guarantee the freshness or cleanliness of the air, nor effectively support any quarantine requirements."

The third reason is the inadequacy of the cruise ship's prevention measures (at least until COVID-19). "In terms of routine infection prevention and disinfection, the implementation of self-quarantine on a ship can be lacking, including efforts regarding the effectiveness and pertinence of disinfection action. To combat the spread of infection, it would be necessary to increase the frequency and intensity of the disinfection of public places, and sites with poor ventilation would require additional attention." Of course, this is the area where one would expect that the cruise companies have advanced the most since nothing in the magnitude of the COVID-19 had affected the industry before.

The fourth reason had to do with limitations by the cruise companies concerning the health of their passengers. "Since the large groups of passengers inhabit limited spaces, the density of personnel is extremely high (...) cruise passengers are frequently middle-aged or elderly with a relatively higher vulnerability to common medical conditions and less resistance to diseases. Thus, they are more susceptible to epidemic induced afflictions. Although liners are equipped with medical facilities and medical personnel, there are limitations to the medical care which can be provided, implying that the capacity to deal with outbreaks is not that which would be expected ashore."

The fifth and last reason is the lack of capacity by port authorities to handle large outbreaks of infections. "There is no emergency plan for the prevention and control of infections in cruise ships. The United States occupies the core of international cruise tourism market and is the largest source of tourists. It has accumulated rich experience in the process of cruise operation and management (...) When the ship encounters disasters such as fire, reef, and security threat, the United States Coast Guard launches corresponding cruise emergency rescue plans. However, this mechanism does not have an emergency plan for the outbreak of infections and gathering-related epidemics. While the CDC focuses on the prevention and control of intestinal infections for passenger vessels, there is no targeted plan for respiratory infections. Furthermore, other countries with developed cruise tourism industry also have similar issues relating to epidemic management (...) Although cruise lines and berthing ports are relatively fixed, different ports have different emergency response capabilities. The lack of international cruise emergency drill may also lead to failure in responding quickly and effectively during an emergency."

We have no doubt that the cruise industry has taken stock regarding the third and fourth reasons and improved substantially its protocols and that regarding the fifth reason one could also expect improvements and better coordination between port authorities and cruise companies (any feedback on that would be quite useful, of course). However, what about the first and second reasons? We know that designing a cruise could take many months and that not just the best naval architects, architects, and designers put their best ideas in place. Besides, we know the aviation industry has been able to cope with similar problems. Are those two flaws--stagnation of microclimates due to airtight structures, and the inability of central air-conditioning to help with quarantines--a problem that the cruise industry has not been able to solve, or do the authors of the study, make generalizations that do not correspond to the latest technologies used on the cruise industry?

Gliese Foundation

October 19th, 2020