Only around 1% of all norovirus outbreaks in the US are believed to occur on cruise ships, yet when they do happen, they can affect a number of people, and they become a prime topic for media coverage.
There have been three incidents on cruise ships in the last couple of weeks that you may have heard of (two confirmed as norovirus outbreaks, and one where norovirus is suspected), which are highlighted here. To put these into some perspective, several of the other norovirus-related happenings in that time span are also presented. (Fair warning, there were a lot of them!)
A few days ago, the Balmoral docked in Portland, Maine, for investigation of a norovirus outbreak that occurred during a 34-night cruise that began on April 16 from Southampton, England. According to the CDC’s Vessel Sanitation Program (VSP), 30% of the passengers (277 out of 915 passengers), as well as nine of its 520 crew members had been sick with norovirus symptoms. It has been suggested that there were sick passengers on the preceding voyage, which the Fred. Olsen Cruise line confirmed as a smaller outbreak and tried to manage with extra sanitation measures and professional cleaners. Of note, the company says they use a longer quarantine time for ill passengers of 48 hours, rather than 24 hours, and only had six passengers in quarantine in their rooms when they arrived in Portland, Maine. Once the ship reached Canada, it went under the jurisdiction of the Public Health Agency of Canada.
Around the beginning of the month and in another part of the ocean, the Disney Wonder was also experiencing an outbreak of gastrointestinal illness. That outbreak ultimately sickened 131 of the passengers (about 5% of the total 2680 passengers) and fourteen of the 991 crew members, as was recently reported by the CDC VSP, and you can see details of their investigation on their website.
Last week, the Carnival Adonia, made famous because it was the first US cruise ship to sail to Cuba in 50 years, had a small number of ill passengers when it arrived back in the US a few days ago. These fourteen passengers were recovering, and it is believed they may have had norovirus. (The number of cases was too low to initiate an official VSP investigation on the ship.)
But what about the other >98% of norovirus outbreaks?
Noroviruses like to be where we are, and are no strangers to schools and universities. There was a possible norovirus outbreak involving at least 30 people at the University of Oregon last week, and investigators are working to determine the source of the illnesses on campus. At the beginning of May in Minnesota, about 20 students at Carleton College had norovirus-like illness, which may have been connected with a nearby restaurant. At the very end of April, a middle school in Buffalo, New York had to close early for a weekend of cleaning. About a quarter of the students were absent, and with a dozen teachers sick, it amounted to hundreds of people. On the other shore in California, another elementary school had 90 students and six employees out with gastrointestinal illness, thought to stem from a student who vomited in a classroom. (On an especially sad note, the outbreak may cause them to cancel a school musical performance.)
Food service establishments were not been spared either in the last couple of weeks, and a few days ago, a Carrabba’s in Michigan may have experienced a small outbreak of norovirus that made over a dozen people sick. It led to the entire restaurant being closed for cleaning and all of their opened food to be discarded. The restaurant even tossed out all of its menus, realizing they could be a fomite because many people handle them. A couple of weeks ago, a restaurant on Carnegie Mellon’s campus had to also temporarily close when about forty people became sick after eating soup or sandwiches at the location. Two employees at the facility had also been sick (but it is unclear from the articles if they were sick before or after the other cases).
Lastly, noroviruses love a good party, and there was an outbreak of gastrointestinal disease following a wedding reception at the end of April in New Jersey (42 of the 150 attendees became sick). It is believed to be norovirus, and the investigation is ongoing. And in a slightly interesting case, about a third of 210 attendees to a Democratic party function in Nebraska in March contracted what turned out to be norovirus. Person-to-person contact was recently identified as the most likely cause, and in particular hand shaking was implicated. The county health department did not find evidence that it was transmitted by food at the banquet or an environmental cause.