Government health officials say there have been 971 cases of measles in the United States so far this year, the most cases since 1994, when there were 963 cases for the entire year.

The Centers for Disease Control and Prevention said Thursday if current outbreaks in and around New York City continue into the fall, the United States could lose its status as a country that has eliminated measles.

"That loss would be a huge blow for the nation and erase the hard work done by all levels of public health," a CDC statement said.

Measles was declared eliminated in the U.S. in 2000, and the CDC says one of the primary reasons is the availability and widespread use of a safe and effective vaccine.

A man walks past a sign advising about a measles o A man walks past a sign advising about a measles outbreak in the Brooklyn borough of New York, April 25, 2019. A man walks past a sign advising about a measles outbreak in the Brooklyn borough of New York, April 25, 2019.

Fighting anti-vaccine propaganda

The CDC, World Health Organization, and other experts are fighting propaganda from parents and anti-vaccine activists who refuse to inoculate their children, insisting the vaccine is dangerous.

"Again, I want to reassure parents that vaccines are safe, they do not cause autism. The greater danger is the disease that vaccination prevents," CDC Director Robert Redfield said. "Measles is preventable and the way to end this outbreak is to ensure that all children and adults who can get vaccinated do get vaccinated."

Before vaccine, 4 million cases

Before 1963, when the measles vaccine was considered perfected, the CDC says as many as 4 million Americans got the disease every year and up to 500 victims died.

The measles virus is highly contagious and is spread primarily by coughing and sneezing.

Along with the refusal of some people to vaccinate their children, the CDC says the current nationwide outbreak is linked to travelers who are suspected of bringing back the virus from countries with their own large outbreaks, including Israel, the Philippines and Ukraine.