The U.S. Centers for Disease Control and Prevention (CDC) has confirmed nearly 900 cases of mumps among people at adult migration detention facilities across the United States in the last year.
The virus swept across 57 detention centers in 19 states, sickening 898 migrants between Sept. 1, 2018, and Aug. 22, the CDC said Thursday.
Thirty-three staff members were also infected.
The CDC said the virus continues to spread as more migrants are arrested or transferred between facilities.
Mumps is a contagious virus that causes swollen glands, puffy cheeks, fever, headaches and, in severe cases, hearing loss and meningitis.
Mumps outbreaks are rare in the U.S. because of vaccinations, but the disease is easily transmittable in spaces where people have close, prolonged contact.
The CDC said most of those infected were men who caught the virus while in detention.
Immigration and Customs Enforcement spokesman Bryan Cox said all detainees go through a medical screening within 24 hours of arriving at the facilities.