Although HHV-6 infection is often undetectable, multiple studies have utilized tissue biopsy on large intestine tissue specimens to show that HHV-6B infection can induce gastrointestinal dysfunction even in the absence of detectable viremia. In one study among patients suffering from gastrointestinal dysfunction, HHV-6B DNA was detected in the nuclei of both goblet cells and histiocytes in the large intestinal submucous, suggesting that HHV-6B can directly infect and reactivate in these cells (Amo 2003).
Severe diarrhea and colitis sometimes present in patients that have experienced HHV-6B reactivation following both solid organ (Lempinen 2012, Lamoth 2008, Delbridge 2006, Pilmore 2009) and stem cell transplantation (Mousset 2012, Amo 2003, Hentrich 2005). One group detected HHV-6 in 50-71% of upper gastrointestinal tract biopsies taken from stem cell transplant patients who experienced severe vomiting or diarrhea in the first year following transplant (Mousset 2012). Additionally, the simultaneous presence of HHV-6 and adenovirus in biopsies of young children is highly associated with intestinal intussusception (Lappalainen 2012). HHV-6B-induced gastrointestinal dysfunction has been successfully treated with antiviral therapy (Breddemann 2007, Delbridge 2006, Pilmore 2009).