Nightly News | August 27, 2013
>>> along the eastern seaboard tonight there's been a troubling mystery, what's been killing so many dolphins . scientists believe they figured it out. our chief environmental affairs correspondent anne thompson reports.
>> reporter: they are some of nature's most beautiful and graceful creatures. the bottle nose dolphins are in trouble. from new york to north carolina , federal scientists report 357 dolphins died between july 1st of this year, and august 26th . a sudden and dramatic increase during a period that typically sees 36 deaths. federal officials say the cause is the morbilly virus. the human cause of the strain causes measles. unlike people, there's no way to vaccinate wild dolphins .
>> we're expecting the virus and the impact of the virus is going to spread southward.
>> however, scientists say the strain killing the dolphins cannot be passed to beach goers and swimmers. in dolphins , the morbillivirus weakens their system, causing them to lose weight and making them susceptible to other diseases. this is the biggest die off of these mammals in 25 years. today the source of the virus remains a mystery. scientists will look to see if contributing factors, such as man made pollution make the dolphins more vuler ifable to this fast moving disease. anne thompson nbc news, new york.