A very serious illness affecting the internal organs. Its occurs when the host (often non-black) is housing a younger middle age soulful black woman. This said black woman often grows inside of the host affecting their music taste, vernacular, and often accompanied by loud outburst of soulful hearty singing without warning. This persist undetected until the untimely end of the incubation process (often in the month of February , during Kwanzaa, or sometime at soulful R&B concerts and occasionally at church services). resulting in the host being absorbed and taken over completely. Although not fatal, there is a largely notable increase in attitude, melatonin, and overall spice and sassiness once this process has run its course. ...Do your part to detect AIS as early as you can.
"Boy Samantha keeps breaking out in bellows of soulful song, i hope she doesn't have Acute Intra-sistaitis."