Almost 900 migrants were exposed to mumps while in immigration custody in the first such reported outbreak of the contagious viral disease in U.S.-run detention centers, a new report from the Centers for Disease Control and Prevention reveals.

The CDC said Friday that a total of 898 confirmed and probable mumps cases were reported among adult migrants detained in 57 of all 315 facilities housing Immigration and Customs Enforcement detainees across 19 states between Sept. 1, 2018 and Aug. 22, 2019.

Almost half of all the mumps cases, almost 400, were reported in facilities in Texas. According to the CDC, the outbreak began in October and it involved five cases in which migrants had been transferred between two facilities within the state.

Only four of the facilities exposed to mumps are run by ICE. Another 34 facilities are run by private companies who contract with ICE, while 19 are county jails that house detained migrants.

The CDC concluded that 84 percent of all the patients infected, 758 migrants, were exposed to mumps while in ICE custody, whether it was at a facility run by the agency or a company contracted by the agency.

Only 43 people, or 5 percent, were exposed to the virus before apprehension. The custody status of 97 migrants, or 11 percent, was unknown at the time of their exposure.

Thirty-three additional cases occurred among staff members in these facilities.

The high number of mumps cases "prompted a coordinated national outbreak response" from the CDC and ICE.

"As of August 22, 2019, mumps outbreaks are ongoing in 15 facilities in seven states, and new introductions into detention facilities through detainees who are transferred or exposed before being taken into custody continue to occur," the CDC said in a statement.

Approximately 150 mumps outbreaks and 16,000 cases have been reported in the United States since 2015. Most of these cases have occurred in universities, schools and at athletic events, but this is the first report of mumps outbreaks in detention facilities, according to the CDC.

While mumps vaccination efforts vary across detention facilities, the CDC recommended detention centers follow local or state health department protocols to prevent and respond to outbreaks.

The CDC also encouraged facilities to report cases accordingly, and to vaccinate both detainees and staff members" who are at an increased risk for mumps."

NBC News has reached out to ICE for comment.

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