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West Nile virus
In most cases of arbovirus infection, symptoms are mild, last 3 - 5 days, and resolve without becoming serious. In fact, the infection is generally unrecognized as anything other than a mild flu.
Prognosis for severe encephalitis depends on many factors, including the following:
In severe cases of encephalitis, the swelling of the brain inside the skull places downward pressure on the brain stem. The brain stem controls vital functions, such as respiration and heartbeat, and if the pressure becomes too severe, these vital functions can cease and cause death.
Coma is a common symptom in patients with severe encephalitis, but does not necessarily predict a fatal or severe outcome. In one study of Eastern equine encephalitis, some survivors averaged 5 days in a coma and had no or only mild-to-moderate complications afterward. One patient was in a coma for 9 days and had only mild complications afterward.
Survivors of encephalitis commonly experience neurologic consequences, which can be long-term and even permanent. The degree and type of brain damage can vary from mild-to-severe and from focal (in one part of the brain) to multifocal (several parts of the brain) to diffuse (throughout the brain).
The location and severity of the infection largely determines the pattern of brain damage and therefore its effects, which can be:
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