As measles cases continue to rise around the globe, the World Health Organization warns it’s a signal that other disease outbreaks could soon follow.

The surging number of measles cases around the world is a stark warning sign that outbreaks of other vaccine-preventable diseases could be next, the World Health Organization warned Friday.

“It’s crucial to understand why measles matters,” said Dr. Kate O’Brien, director of the WHO’s Department of Immunization, Vaccines and Biologicals. “Its high transmissibility means that even small drops in vaccine coverage can trigger outbreaks, like a fire alarm going off when smoke is detected first.”

That is, measles is often the first disease to pop up when vaccination rates overall drop.