Norovirus diagnostics and serology in travelers' diarrhea-where do we go from here?

Norovirus: new developments and implications for travelers' diarrhea

Noroviruses are the leading cause of acute gastroenteritis in the United States and are responsible for at least 50 % of acute gastroenteritis outbreaks occurring worldwide each year. In addition, noroviruses have caused outbreaks on cruise ships, in nursing homes and hospitals, and in deployed military personnel, but its role in the etiology of travelers’ diarrhea is not well defined. The aim of this review is to describe the role of noroviruses in travelers’ diarrhea in terms of epidemiology, current diagnostics, treatment and vaccine development efforts. Studies have shown prevalence rates of noroviruses in travelers’ diarrhea cases ranging from 10–65 %. It is likely that norovirus prevalence rates are highly underestimated in travelers’ diarrhea due to rapid onset, short duration of the illness, limited availability of laboratory facilities, and the fact that most clinical laboratories lack the diagnostic capability to detect noroviruses in stool. Further, additional studies are needed to accurately determine the true prevalence rates of norovirus as an etiologic agent of diarrhea among travelers to different regions around the world. With the rapid progress in the development of a norovirus vaccine, travelers could serve as an ideal population for future norovirus clinical trials.

Relative cost-effectiveness of a norovirus vaccine in the deployed military setting compared to a vaccine against Campylobacter sp., ETEC, and Shigella sp

Norovirus (NoV) has been identified as a significant cause of acute gastrointestinal illness among deployed military troops. We conducted a cost-effectiveness analysis for the use of a NoV vaccine in the military using a previously developed model that evaluated vaccines for ETEC, Campylobacter, and Shigella for prevention of non-outbreak associated travelers' diarrhea. Under conservative assumptions, acquisition of a NoV vaccine by the Department of Defense is estimated to result in a cost-effectiveness ratio per duty day lost to illness (CERDDL) of $1344 compared to a CERDDL of $776, $800, and $1275 for ETEC, Campylobacter sp., and Shigella sp., respectively compared to current management strategies. The absolute value of avoiding a duty day lost is likely to vary under different scenarios, and further study is needed to evaluate how improved diagnostics and prevention of outbreaks may impact the relative value of this vaccine. Overall, this study demonstrates the utility of a previously established evidence-based decision tool for prioritization of vaccine acquisition in an important target population.