What Causes Infiltration Of Lungs Along With Pneumonia?

my granddaughter has been diagnosed with possible pneumonia. However they called back today saying that she had infiltration in her lungs. I m very concerned about this I ve been trying to research and I know understand that it s possible with pneumonia would there be any other causes she has no fever she s not going through any of the signs and symptoms of pneumonia or throat ears are clear she does have a little bit of run out of but other than that I m just very concerned can you lead me in some direction?