Hi Violet123

Septic meningitis is usually caused by a pyrogenic bacterial infection.

Aseptic meningitis is often a diagnosis by exclusion. It can arise from a viral infection (for example enterovirus, cytomegalovirus or herpes virus - if so, these can usually be detected in CSF using the polymerase chain reaction). Sometimes aseptic meningitis can arise from a mycobacterial infection - this can be hard to detect.

These are ideas which it might be helpful for you to raise with your immunologist.

All the best.