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Norovirus has become a common scourge, generally perceived as an extremely disruptive but self-limiting nuisance. There is another aspect of this emerging virus that has been somewhat overshadowed: It is a “debilitating and life-threatening infection in immunosuppressed patients,” researchers report.1
Two NIH investigators recently summarized the mechanisms, scope and treatment of norovirus gastroenteritis in immunosuppressed patients. Not surprisingly, they found that vigilant hand hygiene is the best method to prevent transmission and protect these patients in hospitals.
Other key findings include:
• Norovirus infection can include symptoms of fever, diarrhea, projectile vomiting, and mimic graft versus host disease in transplant patients.
• As compared to the disease in immunocompetent hosts, in the immunocompromised host the disease last for years and shedding of the virus may be indefinite.
• Disease is usually self-limited in the immunocompetent, but little therapy may available for the more severe illness in the immunocompromised host.
• Infection in the immunocompromised host can cause malnutrition, dehydration and worsen the underlying immunocompromising illness.
• There are several assays available in the clinical microbiology laboratory including those based on RT-PCR, but not all labs will offer these tests. More study is required to understand the utility of the different diagnostic assays. Norovirus testing should result more often from the consideration of this infection in immunosuppressed patients with acute and chronic diarrhea
• Immunocompromised patients may have a diverse population of mutating noroviruses, including many so called “low-frequency variants” in chronic infection. In one study 80% of surfaces in a children’s unit were contaminated with 21 different noroviruses.
• Both T-cell and B-cell responses seem necessary for adequate immune surveillance and viral clearance. Increasing CD4 cell count in HIV patients improved symptoms.
• Commonly used antiviral agents do not allow viral clearance. Some success with improving symptoms has been reported with nitazoxanide, an antiprotozoal drug.