My dad 54 old had fever and headache, now he is sleepless, talks non stop, acts weird, gets angry on people at home, sometimes cries. what's could be ?

Possible delirium: Dear karthika, because your father's current symptoms are preceded by the fever and headache, he could have a medical condition changing his behavior. Sudden and acute onset, alteration in attention, and fluctuating course are the central features of delirium, which can be caused by a wide variety of things including meningitis and drug intoxications. He needs emergency evaluation.