Carnival shares were off nearly 6%, while Royal Caribbean fell nearly the same amount as of 10:30 a.m. ET, after reports this weekend that two passengers aboard Royal Caribbean’s Adventure of the Seas ship tested positive for COVID-19.

The guests, who were unvaccinated and under the age of 16, were disembarked in The Bahamas and were sent home to Florida after the virus was detected in a routine test on board the ship.

Carnival, last Thursday, also said it expected to lose $2.1 billion in the second quarter, though it’s unclear if that’s affecting traders’ thinking Monday.

The incident fanned fears among investors for the cruise industry, which sat in dry dock for 15-months due to the pandemic. It was on board a Princess Cruises ship—the Diamond Princess—that 712 people became infected in one of the first major outbreaks outside of China. Passengers were quarantined on the ship beginning Feb. 1 and many who were not infected were not permitted to leave their cabins until Feb. 17 or Feb. 19.

The cruise industry has made several changes to how it handles passengers, ranging from reduced capacity to changes to the buffets. Still, bookings are currently slow, even as Americans begin venturing out and actively vacationing in 2021.

Carnival and Royal Caribbean aren’t the only cruise lines suffering Monday. Norwegian Cruise Line was off 5% in early trading as well.