What is "cave disease"?

(CNN) -- The dramatic rescue of 12 boys and their soccer coach from a flooded cave system in Thailand captured the world's attention. And now that they are out safely, the next step is to check and monitor their health.

Photo: Royal Thai Navy

The group spent more than two weeks inside the cave, and that can cause several medical issues. One of the biggest concerns is histoplasmosis, or "cave disease."

"Basically these fungus spores that are the result of bird and bat droppings can get into the air, get into the lungs, and cause infection," says CNN Chief Medical Correspondent Dr. Sanjay Gupta.

Doctors are also concerned that their extended time in that dark and damp space without adequate nutrition and water could have compromised their immune systems.

"Their bodies start to acclimate to that cave. They're not exposed to natural light. Their bodies start to change, their immune system starts to function less robustly, and what would otherwise be a seemingly harmless infection can become more dangerous."

Three boys are being treated for minor cases of pneumonia. The hospital will monitor the boys and their coach and keep them in an isolation ward at the hospital for at least a week, in order to build up their immune systems.