Scientists have found the strongest evidence yet that a virus causing brain disease in animals can infect people and possibly plays a role in some psychiatric illnesses.
Genetic material from the virus was found in four hospitalized psychiatric patients in Germany, researchers report.Two patients had severe recurring depression, one had obsessive-compulsive disorder with alcohol abuse and the fourth had a mood disorder and epileptic seizures.
Other studies have found indirect evidence of infection in people with depression, manic-depression or schizophrenia.
It is still not known whether the virus causes human psychiatric disease or how often it might be involved, said the study's lead author, Liv Bode. The virus may worsen disease symptoms, but that is only speculation, said Hanns Ludwig, another author.
Infection by the virus, called Borna disease virus or BDV, has been reported in horses, sheep, cattle and other animals, mostly in central Europe. Infection in animals can affect behavior and cause other symptoms, depending on the species infected. In horses and sheep, for example, the virus kills brain cells, causing severe hyperactivity, staggering and paralysis.
Scientists have found evidence that suggests human infection with BDV in Germany, Africa and the United States, Bode said. It's not clear whether human infections would come from the animal virus or a separate human strain.
Bode is a virus specialist at the Robert Koch Institute in Berlin. Ludwig is a professor of virology at the Free University of Berlin. They report the findings with colleagues in the March issue of the journal Nature Medicine.
Dr. Kathryn Carbone, an infectious disease specialist at the Johns Hopkins University School of Medicine, said the work is the strongest evidence so far that BDV can infect people.
But the finding falls short of proof, she said.