Significance
Human mucosal surfaces contain a wide range of microorganisms.
The biological effects of these organisms are largely unknown.
Large-scale metagenomic sequencing is emerging as a method
to identify novel microbes. Unexpectedly, we identified DNA
sequences homologous to virus ATCV-1, an algal virus not
previously known to infect humans, in oropharyngeal samples
obtained from healthy adults. The presence of ATCV-1 was associated
with a modest but measurable decrease in cognitive functioning.
A relationship between ATCV-1 and cognitive functioning
was confirmed in a mouse model, which also indicated that exposure
to ATCV-1 resulted in changes in gene expression within
the brain. Our study indicates that viruses in the environment not
thought to infect humans can have biological effects.