Washington (CNN) US Immigration and Customs Enforcement has placed 5,200 adult immigrants in quarantine after being exposed to mumps or chicken pox, a dramatic jump from just a few months ago, the agency says.

ICE has recorded cases of either mumps or chicken pox in 39 immigrant detention centers nationwide, an ICE official tells CNN.

Of the 5,200 detainees in quarantine across those centers, around 4,200 are for exposure to mumps. Around 800 were exposed to chicken pox and 100 have been exposed to both.

The Department of Homeland Security has repeatedly warned of the toll the increasing number of migrants at the border has taken on the department. This week, Acting DHS Secretary Kevin McAleenan urged lawmakers for additional funding to assist operations, calling the crisis "unlike anything our country has ever faced."

In May, nearly 133,000 migrants were apprehended by Customs and Border Protection -- the majority of whom were families and unaccompanied children . Many of them turn themselves in to Border Patrol.

Just because individuals are quarantined doesn't mean they have the mumps, but they've at least been exposed to it. From September 2018 to June 13, 297 people in ICE custody had confirmed cases of mumps, proven by blood test.

There are around 52,000 single adults in ICE custody overall.

The agency has previously dealt with contagious diseases, like the measles, the flu and chicken pox, but last September was the first time the agency recorded mumps cases. It's not clear where the disease derived from or how it spread. Seventy-five percent of the immigrants coming into ICE custody come from the border, though immigrants might also interact with inmates at jails, some of which also hold immigrants.

"I think there is heightened interest in this situation because it's the mumps, which is a new occurrence in custody, but preventing the spread of communicable disease in ICE custody is something we have demonstrated success doing," said Nathalie Asher, ICE executive associate director for enforcement and removal operations.

"From an operational perspective, the impact is significant in the short and long term and will result in an increase in cohorted detainees' length of stay in detention, an inability to effect removal of eligible cohorted detainees, and postponing scheduled consular interviews for quarantined detainees," she added.

ICE quarantines individuals for 25 days from the last incubation period.

The official said staff has also been put on alert. "This week, the ICE Health Service Corps issued a reminder to senior field leadership reminding their staff to review vaccination records and take appropriate actions," the official said.

The number of detainees quarantined has jumped dramatically from earlier this year. There were 2,287 detainees in quarantine for "exposure to a detainee with a contagious condition," as of March 7, ICE said.

Mumps is a contagious disease

There have been 1,002 cases of the mumps reported in the United States this year as of May 24, according to the US Centers for Disease Control and Prevention.

Mumps is a disease that is caused by a virus. It is spread through saliva or mucus by coughing, sneezing or talking, and by sharing eating utensils or cups. It can also spread when an infected person touches items or surfaces that are then touched by someone else who picks up the virus.

The best way to prevent mumps is with a vaccine, and the measles, mumps and rubella (MMR) vaccine is 88% effective for mumps when two doses are given, the CDC says.

Outbreaks usually occur among people who have close contact with an infected person or people, such as on college campuses and among sports teams.

Symptoms can appear 12 to 25 days after a person is infected and can include fever, headache, muscle aches, being tired and loss of appetite. The hallmark, though, is swollen glands under the ears that are tender. But not everyone has symptoms, especially if they are experiencing a mild case of the illness.

When there is a mumps outbreak in a facility where adults are detained, the ICE Health Service Corps recommends the vaccine be given "to detainees with known exposure to at least one laboratory-confirmed person with measles, mumps or rubella." It's also recommended that catch-up vaccinations be given to those younger than 18.

"Our detention facilities work with local health departments and make sure they're complying with state health code and make sure that their local health department is aware of the existence of mumps in the facilities," said the ICE official.

Overcrowded border facilities

DHS officials have said the sheer volume of people coming across the border is overwhelming facilities. McAleenan told lawmakers this week that the increasing number of migrants has hurt the morale of border officials and exposed them to sicknesses.

"Their morale is impacted. They're tired. A lot of them have gotten sick. They've been exposed to flu, chicken pox, measles, mumps -- all kinds of challenges in terms of the medical care," McAleenan said. "They're spending time overnight in hospitals instead of patrolling the border."

Late last month, the Department of Homeland Security inspector general released a report detailing some of the issues facing border patrol facilities amid the swell of migrant arrivals.

In particular, the IG found "dangerous overcrowding" and unsanitary conditions at an El Paso, Texas, Border Patrol processing facility following an unannounced inspection, according to a new report.

The IG found "standing room only conditions" at the El Paso Del Norte Processing Center, which has a maximum capacity of 125 migrants. On May 7 and 8, logs indicated that there were "approximately 750 and 900 detainees, respectively."

"We also observed detainees standing on toilets in the cells to make room and gain breathing space, thus limiting access to the toilets," the report, which was first obtained by CNN, states.