Notably, the radii of Fos and Jun plumes were typically not much more than one-half the extent of virus infection (0.3 mm average radius Fos/Jun plumes versus 0.5 mm average radius virus infection; Fig 2B), suggesting that laser illumination neurobiologically excites only the proportion of infected neurons that are close enough to receive light intensity exceeding neuronal illumination thresholds needed to trigger immediate early gene transcription and translation into protein. This evidence concerns the gene JUN and viral infectious disease.