The other 7 year old girl from Guatemala died of similar symptoms. It sounds like severe dehydration. The hospital is probably not running an osmotic level to find the dehydration. However, NIH will be able to comment on any childhood illnesses that may be endemic to Guatemala.
These children are also now exposed to USA illnesses they have no immunity to that are airborne or possibly in food or water at the facility. At any rate it is a complicated picture with these children. They need intense assessment by epidemiologists from NIH to develop a protocol for the Border Patrol.
Something as simple as an intestinal parasite, like Giardia they picked up along their travel could be affecting them and causing a septic shock. I remember reading due to the Mexican border road block some of the migrants were taking a path through the jungle. The NIH really needs to be involved at this point as soon as is possible. Damn the government shutdown! Thank you.
The Border Patrol can also ask local Board of Health to coordinate any assessments with NIH. They may already know what issues the Border Patrol may be facing with these children. These children are not average everyday children as they have lived an impoverished life with a great deal of violence from day to day. It could be anything. But, most likely dehydration is the best place to start. The adults could be experiencing dehydration too, but, adults are more resilient to it. Good luck.