Fatal encephalitis associated with borna disease virus 1
The present case has been published in NEJM.

Viral encephalitis developed in a previously healthy 25-year-old man, and he died 1 month after the onset of symptoms. He was an engineering student and lived in Central Franconia, Bavaria, Germany, with his family and two dogs and two cats. He often spent time outdoors, but he had not traveled recently.

After a 5-day episode of fever and headache, followed by fatigue and confusion. He was disoriented and had psychomotor slowing, multifocal myoclonic jerks, and an unsteady gait. Cranial computed tomography and MRI on admission showed no pathological findings. Analysis of the CSF showed lymphocytic pleocytosis (7 cells per cubic millimeter on day 1 and 68 cells per cubic millimeter on day 6).

Electroencephalography performed on the day after admission (day 2) revealed signs of diffuse encephalopathy with generalized abnormalities, intermittent slowing with theta waves (<8 Hz), and an intermittent alpha rhythm, but no signs of epileptic activity (Fig. S1 in the Supplementary Appendix, available with the full text of this letter at NEJM.org).

The patient’s body temperature peaked at greater than 39°C each day, and continuous fever (temperature >38.5°C) was present from day 3 onward. He became progressively lethargic; because of declining consciousness and deteriorating brain stem reflexes, his trachea was intubated and mechanical ventilation was begun, and he was transferred to the intensive care unit on hospital day 4.

On day 7, cranial MRI revealed abnormal findings on T2-weighted and fluid-attenuated inversion recovery imaging, as well as leptomeningeal and dural contrast enhancement suggestive of meningitis. The lesions were progressing, and MRI angiography performed on day 20 revealed generalized brain edema, transtentorial and transforaminal herniation, and severely decreased cerebral blood flow.

Death was declared on day 23, and an autopsy was performed. The differential diagnosis focused on encephalitis with an infectious (viral, bacterial, or fungal) or autoimmune cause, but a panel of tests was uninformative (see the Supplementary Appendix). Next-generation sequencing of brain samples obtained after the patient’s death revealed the presence of Borna disease virus 1 (BoDV-1), with a total of 39,000 reads covering the complete BoDV-1 genome of approximately 8.9 kb.

During the 1980s and 1990s, several studies implicated BoDV-1 as a possible cause of depression and other psychiatric disorders in humans. However, these associations, which were based on antibody tests, an unvalidated antigen assay, and results of a polymerase-chain-reaction assay, lacked reproducibility, and the presumed human bornavirus isolates showed high sequence similarity to laboratory strains.

A more recent study did not show that Mammalian 1 bornavirus is a cause of psychiatric disorders. However, this case shows that BoDV-1 can be a cause of severe encephalitis.

Read in detail about the case here: https://www.nejm.org/doi/full/10.1056/NEJMc1800724