VILANO BEACH, Fla. -

More dead dolphins were found along the coast of northeast Florida on Monday.

About a dozen bottlenose dolphins have washed up dead in the last two weeks. Biologists believe they're dying from a measles-like disease called morbillivirus, which has killed more than 800 dolphins off the East Coast from New York to Florida since July and is likely to continue.

Marineland Dolphin Adventure in St. Johns County is taking extra precautions to make sure its dolphins don't get infected.

IMAGES: Dead dolphins wash up on area beaches

One dolphin about a month old washed up dead at Anastasia State Park on Monday. Another bottlenose dolphin washed up on Ponte Vedra Beach.

Recovery crews prepared to perform necropsies on both to determine how they died.

"We come out here and it's one of our favorite things to watch is the dolphins play in the surf, and it's just really sad to watch," said Debbie Varnes, who's visiting the area for Thanksgiving.

Another popular place to watch dolphins play is Marineland, but Varnes and her 7-year-old daughter likely wouldn't be allowed in right now because they've been watching the recovery process so close. As part of precautionary measures Marineland is taking to make sure its dolphins don't get infected, it's asking people who have been near dolphin strandings to come back another time.

Staff like Georgia Aquarium field coordinator Matthew Denny also can't go into the park anytime soon because morbillivirus is highly contagious.

"There are no documented cases of humans contracting cetacean morbillivirus, but we can serve as a carrier or a vector and transfer it to these healthy dolphins that reside at Marineland or any sort of marine park like that," Denny said.

Federal wildlife officials have declared this deadly dolphin outbreak an unusual mortality event that happened once before in the 1980s. Researchers are hoping they use what they learn to prevent something similar from happening in the future.

One volunteer on Monday pulled out a few of one dead dolphin's teeth. It's just one of many samples that they'll use to determine the cause of death and any diseases the dolphin may have had.

"Every sample that we can obtain is very critical, whether it be samples for genetics, blubber samples for contaminant load, teeth samples for aging," Denny said. "Because they actually lay down a layer of enamel every year so you can almost count like tree rings to get an age estimate, but every sample is critically important to get the root of what type of diseases they might be contending with."

That information will hopefully help conserve and protect the creatures and ultimately humans.

"This outbreak is not necessarily isolated to just dolphin populations, it's a barometer for the health of the ecosystem, which we all depend on," Denny said.