A probe into the disturbing number of dolphin deaths in Virginia and other mid-Atlantic states has a turned up a cause. Sadly, it may continue into the spring.

The National Ocean and Atmospheric Administration believes a virus called the cetacean morbillivirus, “which is similar to measles in humans or canine distemper in dogs,” is causing the dolphins to strand.

To date, 32 dolphins tested from all five states are either suspect or confirmed positive for morbillivirus. For 11 samples, genetic sequencing has confirmed this finding. Veterinary pathologists have also looked at eight animals and determined that detected changes in dolphin tissues are consistent with morbillivirus infection in all tissues analyzed. Additional testing is being conducted on 27 other animals.

A few tested animals were found to also have Brucella sp. bacteria lesions in their joints or brain tissue. Brucella is a type of bacteria that causes brucellosis and has been implicated in other marine mammal stranding cases in the Gulf of Mexico, Atlantic and Pacific coasts since 2010. Brucella has never been documented in humans after direct exposure to marine mammals, though there was a single case of occupational exposure in a laboratory worker who was collecting samples from an infected dolphin. Therefore, the risk of transmission of Brucella bacteria to animal care workers is likely low.

According to the NOAA, 291 dolphins have died since July. The NOAA sadly reports that there is “no way to currently stop the spread of the virus.”