Brain infections, or encephalitis, occur when pathogens like viruses, bacteria, fungi, or parasites invade the brain or its surrounding tissues. Common causes include viral infections such as herpes simplex, tick-borne viruses, or the rabies virus. Bacterial infections can arise from conditions like meningitis or as a complication of other infections. These infections can trigger inflammation, leading to symptoms such as headache, fever, confusion, seizures, and in severe cases, coma or death. Risk factors include a weakened immune system, recent travel to areas with high infection rates, and certain medical conditions. Early diagnosis and treatment are crucial for recovery.