Last year, a report by the Cruise Lines International Association (CLIA) predicted, “Intent to cruise is higher than it was in December 2019 – continuing a trend that began in the last quarter of 2020.” Earlier they also communicated that the global cruise capacity was forecast to grow 19% to more than 746K lower berths from 2022 to 2028.

According to CLIA, attracting 4 million new-to-cruise travellers is the key to meeting the increase in global cruise capacity projected from 2023 to 2025. Every 1% increase in first-time cruise travellers (international travellers who have never cruised and are open to cruise) is equivalent to 4 million new-to-cruise travellers.

In the post-covid era, the industry has put its utmost effort to facilitate growth of the industry. According to a recent market research study published by Custom Market Insights, the demand analysis of Global Cruise Tourism Market Size & Share Revenue was valued at approximately USD 5,298.9 Million in 2022 and is expected to reach USD 14,645.4 Million by 2032, at a CAGR of 11% between 2023 and 2032.

As per the report, there are multiple factors boosting the growth of the industry. Changing consumer preferences, including a growing interest in experiential travel, adventure tourism, and luxury experiences, are significantly impacting the cruise market. Economic stability and disposable income levels are influencing travellers’ decisions to embark on cruise vacations. So, apparently there is no reason to slow down the growth momentum of the industry.

Unfortunately, since 2023, norovirus outbreaks on cruise ships have started growing at an unprecedented scale. Although it is not a new or unknown pathogen, the cause of concern originated when in the mid of the previous year the number of cases exceeded that of any year over the past decade.

As per a cautionary statement by the Wyoming Department of Health (WDH), US, “Commonly described as ‘stomach flu’ or ‘food poisoning,’ norovirus is spread when people eat contaminated food or touch contaminated surfaces, or through close contact with someone already sick.”

Readers may think – then what is the relation between norovirus and ventilation? To be precise, I would like to draw everyone’s attention on a statement issued by the National Services Scotland (NSS). They say – although norovirus primarily spreads through contact, at times it is airborne too. Thus, in this article, I will concentrate on how improved ventilation can help in controlling the spread of norovirus – and the ideas gained from a recent research work.

Why to take norovirus seriously?

According to a CDC report, “Worldwide, about one out of every five cases of acute gastroenteritis (inflammation of the stomach or intestines) that leads to diarrhea and vomiting is caused by norovirus.”

This is the most common cause of acute gastroenteritis, annually causing an estimated 685 million cases. About 200 million cases are seen among children under 5 years old, leading to an estimated 50,000 child deaths every year, mostly in developing countries. However, norovirus illness is a problem in both low- and high-income countries. Every year, norovirus is estimated to cost $60 billion worldwide due to healthcare costs and lost productivity.

Norovirus illnesses and outbreaks are usually more common in cooler winter months. Most outbreaks occur from November to April in countries above the equator, and from May to September in countries below the equator. However, in places closer to the equator, norovirus may be less seasonal.

Why is controlling spread of virus in cruise ships important?

According to NSS, “Norovirus spreads very easily in public places such as hospitals, nursing homes and schools. You can catch it if small particles of vomit or stools (poo) from an infected person get into your mouth through close contact with someone with norovirus who may breathe out small particles of the virus that you then inhale.”

They explain – when COVID-19 began to spread across the globe, its effects were significantly pronounced on cruise ships. Indeed, compared to other population segments, cruise ship passengers became disproportionately infected and often, ironically, stranded on board to quarantine. That’s why focus has been directed at addressing the need for improved ventilation on cruise ships dispersing fresh air in cabins and other enclosed spaces is critical for mitigating viral spread.

What did the scientists from Cyprus found?  

In Physics of Fluids, by AIP Publishing, a group of researchers from Cyprus examined how ventilation can affect transmission of airborne viruses in a typical cruise ship cabin based on guidelines developed before and after the pandemic.

Commenting on their observation, Author Dimitris Drikakis said, “The most recent standards and regulations on room safety regarding the airborne transmission of viruses focus on high rates of air exchange. But this can be inefficient in terms of energy consumption, can compromise passenger comfort as it generates strong air drafts, and most importantly, can spread saliva droplets up to five times more when passengers cough.”

Drikakis and his team conducted simulations for virus droplets from a cough in a typical cruiser cabin that accommodates two or more people, with different ventilation rates and different positions of the person emitting the cough. Computational fluid dynamics testing ranged from 1.5 to 15 Air Changes per Hour (ACH) to capture all possible scenarios, from minimal ventilation to rates exceeding the most recent recommendations.

He further added, “The study reveals that a higher ventilation rate is not the best strategy to avoid spreading airborne diseases. Complete evaporation of the saliva droplets may not necessarily mean all viruses or bacteria become instantly inactive. Therefore, we should aim at minimum droplet spreading inside the cabin and different ventilation strategies for occupied cabins.”

After analyzing the results, the team has determined the ideal use of ventilation systems to operate at medium flow rates of around 3 ACH when a cabin is occupied, to increase to 15 ACH for at least 12 minutes after it has been vacated. In this way, the air would be completely refreshed for the next occupants. They also recommend the same minimum time of 12 minutes as a ‘clearance wait time’ for similar-sized rooms with a minimum of 15 ACH.

Pointing to their primary argument, Drikakis said, “Our main argument for the proposed values is the necessity to minimize droplet spreading while maintaining good ventilation levels, comfort and energy consumption. Keeping ventilation at the proposed values reduces energy consumption and improves passenger comfort in contrast to the use of higher ventilation rates.”


According to a recent report of Statista, by the year 2024, the (expected) revenue in the cruises market will reach US$105.20m in India. Also, it is expected to display an annual growth rate (CAGR 2024-2028) of 6.35%, resulting in a projected market volume of US$134.60m by 2028. The number of users in the Indian cruises market is expected to amount to 256.20k users by 2028.

Already around one year ago, we found the outbreak of norovirus at a school in Kerala’s Ernakulam. There are other instances too. Thus, at this juncture when keeping abreast with the growth of the global cruise business, Indian cruise companies are also charting growth, they have to be careful to control the highly contagious norovirus. Although, mostly the virus spreads through consuming contaminated food or touching contaminated surfaces, it also gets transmitted through contaminated air. Thus, all cruise companies have to follow the ways to improve their ventilation practices & procedures to mitigate the chance of spread of norovirus through air.

By P. K. Chatterjee (PK)

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