A measles-like virus is the culprit in 333 dolphin deaths across the East coast; it belongs to an RNA family that also causes distemper in dogs.
The virus, called morbillivirus, hit the dolphin population once before in the 1980s, killing 700, NBC reported.
"We are now calling it a morbillivirus outbreak," Teri Rowles of the National Oceanic and Atmospheric Administration's Marine Mammal Health and Stranding Response Program said, according to NBC.
Out of 33 dolphins that have been tested all but one was found to be infected with the deadly virus.
Experts have warned untrained people to steer clear of dead dolphins because a secondary infection could be dangerous, the Washington Post reported.
"For people not trained in working with these animals and who don't understand the risk, it's much better . . . to stay away from them, particularly if you have open wounds," Rowles told the Post.
The original source of the infection is still unknown, but scientists believe the affected group of animals had lost their immunity to the virus since the 1987 to 88.
There is not much that can be done to help the dolphins, even though the source of infection is confirmed, NBC reported.
"There isn't anything we can do to stop the virus," Rowles said. "In terrestrial populations, there are vaccines that are developed and [that] are easily usable. We don't have a vaccine that can be easily deployed."
The number of deceased dolphins that have washed up on shore is only a fraction of the actual number of fatalities, USA Today reported.
Many of the bodies that have been found on the beach show advanced decomposition,.
"We've definitely gotten reports of floating carcasses that we were not able to recover - and there are plenty of those," Margaret Lynott, the aquarium's stranding coordinator, told USA Today.
The infection is predicted to last until the spring of 2014, it will die off as dolphins become resistant to the disease.
