More than 100 passengers and crew members on a luxury cruise ship were infected with norovirus, the U.S. Centers for Disease Control and Prevention announced on its website last week.

The incident was reported onboard the AIDAdiva cruise ship, which began its ongoing voyage on November 10, 20 days before the outbreak was reported to the CDC's Vessel Sanitation Program. A total 101 people were reported to be ill, which includes 95 of the 2,007 passengers (4.8%) and six of the 640 crew members (0.9%), according to the CDC.

Diarrhea and vomiting were reported to be the predominant symptoms among the infected individuals. AIDA Cruises is reported to have increased cleaning and disinfection procedures, collected stool specimens from infected individuals for testing, isolated the infected passengers and crew members and consulted with VSP about sanitation cleaning procedures and reporting positive cases in relation to the outbreak.

VSP confirmed that it was remotely monitoring the situation and would review AIDA's outbreak response and sanitation procedures moving forward. Cases of the highly contagious norovirus are reported to have doubled in the United States in recent months, according to data shared by the U.S. Centers for Disease Control and Prevention.

Nearly 14% of tests conducted during the most recent week ending November 15 were reported to have yielded positive cases for norovirus, which was twice as much as tests conducted three months prior at 7%. Test positivity measures how many people are confirmed to have norovirus after an illness is suspected, though health experts have acknowledged that it's imperfect, like other forms of measurement, and depends on the number of tests that are ordered, which may vary.

The U.S. had previously seen a record-breaking rate of norovirus cases reported last December at 25%, though cases had been trending down before seeing another spike in recent weeks, according to CDC data. Alabama, Nebraska, Oklahoma, Texas and Wyoming are among the states currently facing the highest number of norovirus cases, with emergency department visits spiking since July, according to electronic health records data from Epic Research.

Norovirus is the most common cause of viral gastroenteritis, an inflammation in the lining of the gastrointestinal tract, and has several common symptoms including nausea, vomiting, stomach pain and diarrhea, though patients are also reported to experience fever, headaches and body aches less commonly. The contagious virus is the leading cause of foodborne illness nationally at 58% annually, with around 2,500 outbreaks reported each year, according to data shared by the CDC.

The Herd with Colin Cowherd