There have been at least 40 confirmed measles cases in California this year, and the United States is seeing its highest case count in 25 years.

Public health officials say travelers are bringing measles back from countries where the disease is common. It’s highly contagious, and can spread quickly in communities with large clusters of unvaccinated adults and children. Major health organizations recommend all children over 12 months old get the measles, mumps and rubella vaccine, with some exceptions.

In California, lawmakers are hoping to make it more difficult for families who oppose vaccination to opt out of school requirements. The proposal, and the measles cases, have prompted debate and a lot of questions.

What do you want to know about the measles cases in California? Tell us in the form below, and our health care reporter Sammy Caiola will work to find you answers.