Hepatitis E Seroprevalence and Seroconversion. Part 4
Entries on the Postdeployment Health Assessment Form were analyzed for symptoms, specifically vomiting and diarrhea, that were suggestive of enterically transmitted disease, possibly including hepatitis E. Comparison between the study subjects and the total Afghanistan‐deployed cohort revealed nearly identical rates of reporting of these symptoms; 28%, 8%, and 7% of service members had experienced diarrhea, vomiting, or diarrhea and vomiting, respectively, during deployment.
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Predeployment anti‐HEV prevalence.Predeployment samples from 16 subjects had detectable total anti‐HEV levels. This gave a predeployment seroprevalence of 1.1% (95% CI, 0.6%–1.7%). All 16 samples were nonreactive for IgM anti‐HEV.
Although higher percentages of seropositive subjects were male, were white, were officers, had attended college, or lived in an urban area prior to military entry, these differences could have been due to chance alone. An age of 35 years was also more frequent among seropositive subjects, although this difference did not reach statistical significance (odds ratio, 2.9 [95% CI, 0.9–8.8]; ). A statistically significant association between birth country and seropositivity was noted, but this was driven by the large number of subjects with missing data. When subjects with missing birth countries were removed from the analysis, the difference was not statistically significant.
Examination of the percentage of subjects with total anti‐HEV by home location when they entered the military found that subjects from the New England division had the highest percentage of seropositivity for anti‐HEV at 4.2% (95% CI, 0.5%–14.3%). Subjects from the East South Central division had the next highest percentage at 2.6% (95% CI, 0.3%–9.0%), followed by the Mountain, West North Central, and Mid‐Atlantic divisions all at 2% (95% CI, 0.3%–7.2%), the Pacific division at 1.1% (95% CI, 0.1%–4.0%), and the West South Central division at 0.6% (95% CI, 0.02%–3.4%). The remaining divisions (East North Central and South Atlantic) had no anti‐HEV–positive subjects.
Anti‐HEV seroconversion. Two subjects developed total anti‐HEV during the time period between the collection of their predeployment and postdeployment serum samples. However, the samples from both subjects were nonreactive for IgM anti‐HEV. This yielded a seroconversion rate of 0.1% (95% CI, 0.02%–0.5%). These 2 seroconverters were deployed in 2003 and 2004, respectively. The subject who was deployed in 2004 reported on the Postdeployment Health Assessment Form experiencing vomiting and diarrhea during the deployment. Neither subject had any hepatitis‐related medical encounters after their return from the deployment.
This study provides the first reported rates of anti‐HEV seroprevalence and seroconversion among US military personnel deployed to Afghanistan. The results of this study suggest a very low risk of anti‐HEV seroconversion during deployment. Our results did not support a hypothesized high risk of exposure of service members to HEV due to outbreaks among Afghan civilians and previously reported hepatitis outbreaks among the Soviet military in Afghanistan in the 1980s. Either the exposure risk was less than expected or the preventive measures implemented during deployments were effective in minimizing exposure to HEV. Food and water precautions were implemented among US forces. These included using only bottled water or water treated by reverse osmosis units. Food was imported and was subject to inspection and testing. In addition, other preventive practices such as encouraging good hygiene and discouraging consumption of local foods may have been effective at minimizing HEV exposures.