The COVID-19 Travel Health Notice level has been raised to Level 4, the highest level, by the CDC, to reflect an increase in cases on cruise ships since the discovery of the Omicron variant.
On ships, even if you've been fully vaccinated and have had a COVID-19 vaccine booster dosage, the virus that causes COVID-19 spreads rapidly among people in close quarters, according to CDC officials.
Airborne transmission certainly accounted for more than half of COVID-19 transmission aboard the Diamond Princess cruise ship, according to Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York.
"As we manage the highly transmissible variant Omicron, the unpleasant lessons learned during the early months of the pandemic involving cruise ships are now coming home to roost," Glatter told Healthline.
The possibility of a superspreader incident, according to Glatter, is an ongoing concern because certain cruise ships may transport up to 3,000 people.
According to him, the three C's — poor ventilation, crowded venues, and close contact — are the most important considerations when hosting a superspreader event.