(NEXSTAR) – Measles was officially declared “eliminated” in the United States in 2000. If things keep going the way they’ve been going in 2025, that designation could soon change.

“Measles elimination status” is achieved in a country or region when there hasn’t been sustained transmission of the virus for a period of 12 months or longer, explained Dr. William Moss, an epidemiology professor at the Johns Hopkins Bloomberg School of Public Health and director of the school’s International Vaccine Access Center, in a media briefing this month.

A country will lose that elimination status once an outbreak extends longer than a year, he said. We recently came close to crossing that threshold, but barely avoided it.

“We’ve gone a quarter of a century with our measles elimination status,” Moss said. “We almost lost that in 2019 when this large outbreak in New York state and New York City almost extended beyond 12 months. It was just shy of 12 months.”

More than 1,200 measles cases were reported that year, largely in area without widespread vaccination, including Orthodox Jewish communities in New York.

So far this year, nearly 500 cases have been confirmed, and the number has been rising every week the Centers for Disease Control and Prevention announces its new tally.

The largest outbreak of 2025 is in West Texas, where the virus has largely spread in undervaccinated Mennonite communities. Studies of past measles outbreaks in Amish communities indicate this wave of new cases could last many months or a year.

Moss said it’s hard to say whether this year’s outbreak, which started in January, will last longer than 12 months, but it’s possible.

“I hope that is not the case and we can get a handle on this through increasing vaccination coverage but it does remain a threat and we could potentially lose our measles elimination status if this continues the way it has.”

In 1978, the CDC announced a goal of eliminating the highly contagious virus. The agency set a deadline for 1982.

The U.S. missed that deadline by quite a few years, but finally achieved elimination by 2000 “thanks to a highly effective vaccination program in the United States, as well as better measles control in the Americas region,” the CDC says.

Vaccine skepticism has increased since the COVID-19 pandemic, but there are early signs more people are getting vaccinated with against measles since the outbreaks in Texas and New Mexico began, the Associated Press reports.