Case Presentation: A 65-year-old woman with a history of deceased-donor kidney transplant 14 years prior (ESRD from hypertension), diabetes mellitus, and hypertension presented with one month of persistent watery diarrhea and abdominal cramping. She had been diagnosed with norovirus one month earlier and managed conservatively but continued to have multiple watery stools daily despite anti-diarrheals. Repeat gastrointestinal PCR panel, C. difficile testing, and ova and parasite studies were again positive only for norovirus.She was afebrile but tachycardic to 120 bpm with blood pressure 90/60 mm Hg. Examination showed dry mucous membranes and a soft, non-tender abdomen. Labs revealed WBC 7.2 K/µL, hemoglobin 9.2 g/dL, platelets 230 K/µL, creatinine 2.43 mg/dL (baseline 1.8), and potassium 2.4 mmol/L. CT abdomen and pelvis showed no acute abnormalities. Her medications included tacrolimus, mycophenolate mofetil, and prednisone 5 mg daily. Despite holding mycophenolate, she continued to have profuse diarrhea requiring IV fluids and electrolyte repletion.Because of persistent symptoms, colonoscopy was performed and demonstrated normal mucosa; biopsies were unremarkable. She was started on nitazoxanide for chronic norovirus infection, with gradual improvement in stool frequency and hydration status.
Discussion: Chronic norovirus infection is increasingly recognized in solid-organ transplant recipients, in whom impaired cell-mediated immunity limits viral clearance. Unlike the self-limited illness seen in immunocompetent individuals, transplant recipients may experience months of watery diarrhea, dehydration, electrolyte abnormalities, acute kidney injury, and recurrent hospitalizations. Because PCR shedding may persist long after symptom resolution, diagnosis requires correlation with clinical course and exclusion of alternative etiologies through stool testing and endoscopic evaluation.Management remains challenging, as no therapies are formally approved or reliably effective. Nitazoxanide is frequently used off-label and has demonstrated in vitro antiviral activity, but randomized data in transplant recipients are lacking. Evidence consists mostly of case reports, small observational studies, and retrospective cohorts. In a retrospective study of 79 transplant recipients, 40% received nitazoxanide and 85% improved overall, though benefit was lower in patients with baseline chronic diarrhea. Adjustment of immunosuppression—particularly reduction or discontinuation of mycophenolate—has the strongest observational support and is consistently associated with symptomatic improvement and decreased viral shedding, though this must be balanced with rejection risk. Intravenous or oral immunoglobulin has been used in select refractory cases, but outcomes are inconsistent and evidence remains anecdotal. Management therefore requires an individualized approach incorporating illness severity, feasibility of immunosuppression modification, and consideration of off-label therapy such as nitazoxanide.
Conclusions: Hospitalists frequently manage norovirus infections, and supportive care remains the cornerstone of therapy. However, in immunocompromised individuals, norovirus may become chronic and debilitating. Awareness of additional management strategies, including immunosuppression adjustment and consideration of nitazoxanide in persistent cases, is essential to prevent complications such as severe dehydration and kidney injury.