Schizophrenia and Other Psychosis
Hearing of voices, Aggressive Behaviors, muttering to self is a sign of psychosis as it less than 1 month it is Acute Psychosis.
It is not fever induced or Delirium because in these conditions the orientation is usually impaired but is not impaired in this question.
In delusional disorder – there is a single non – Bizarre (physically impossible, logically – impossible) and other than that everything is usually normal. In this condition there is hearing of voices, Aggressive and muttering to self, which usually is not there in Delusional disorder.
Diagnostic Criteria of schizophrenia: 2 or more of following for 1 month ( ICD-10)/ 6 months (DSM-V)
3. Disorganized speech
4. Disorganized behavior
5. Negative symptoms viz affective flattening , alogia, avolition, anhedonia , asociality, inattention