I think you might be correct. A virus can cause this but it could also be a hidden genotype that surfaced. A reversal so to speak. Usually you see variegated plants reverting having branches of solid green.
Variegated plants are less hardy than their solid green cousins. Where there is white there is no photosynthesis happening, no making food/energy for the plant's use. Worse, variegated plants in low light are even more hampered. Still, they brighten a room with the punch of white or yellow.