“We have measles outbreaks every year,” he added. Mr. Kennedy has also said in the past that immunizations against measles and some other infectious diseases are unnecessary and risky.

A measles outbreak in Canada's Ontario province continues to grow, with health officials reporting more than 140 cases on Thursday, making it the most severe outbreak in decades.

While there are usually cases and even minor outbreaks reported yearly, the 2025 outbreak is on track to be the largest in six years.

Measles is one of the most contagious viruses known to humans, experts say. Measles has been spreading across the U.S. for the last several weeks, sickening people in at least nine states amid a growing outbreak in western Texas.

Measles was thought to be eliminated two decades ago. But growing mistrust in vaccines has changed that, and now some people may need booster shots for protection.

Here’s what to know about the current measles outbreak, how common the measles is in the U.S., how it spreads and what the symptoms and treatment are.

Before there was a vaccine in 1963, measles infected millions and killed hundreds of people in the U.S. every year. Now, with the first measles death occurring in over a decade, doctors warn that declining vaccination rates are bringing the disease back,