Measles is not often seen in the United States, but Americans are growing more concerned about the preventable virus as cases continue to rise in rural West Texas. Last week, an unvaccinated child died in the outbreak, which involves nearly 200 cases.

Most of the measles cases reported so far this year are in Texas, where health officials are trying to clamp down on a growing outbreak that has sickened more than 150 people. Other states have also recorded measles cases though they trail far behind Texas, including New Mexico, California and New York City.

Dr. Patrick Jackson, a UVA infectious disease expert, warns declining vaccination rates could lead to more outbreaks.

Dr. Ana Montanez is working overtime in Lubbock to contact vaccine-hesitant parents, explaining the grave risks posed by a disease that most American families have never seen, and one that can be prevented through immunization.

Vaccination is the only way to prevent measles infection, a fact the Trump administration has downplayed. Until this year, public-health officials have abided by a simple playbook for measles outbreaks: Get unvaccinated people vaccinated,

The deadly outbreak comes 25 years after health officials declared measles to be eliminated in the United States following an effective vaccination program. But immunization rates have been gradually dropping in recent years,

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.

New York and New Jersey have issued advisories urging residents to be alert for symptoms and to check their vaccination status. Symptoms can include a rash, fever, cough and eye inflammation, and the virus can sometimes cause pneumonia or brain swelling, both of which can be deadly.