41 year old with HIV and fever

This is a 41 year old man with AIDS, CD4 below 10, who presented with shortness of breath and fever. He was admitted to a general ward but trasnferred to the unit a few days later for tachypnea. On the general floor, his vitals were normal except for some tachycardia. He was 97% on 2 l NC. CXR:



a full workup was done to look for infectious source.
sputums: AFB negative x 3, fungal negative. PCP negative (no PCR, no bacteria
CSF - negative for infection.

What kinds of things could be causing these findings and what would you do?