Abstract
Shigellosis is a major public health concern in China, where waterborne disease outbreaks are common. Shigellosis-containing strategies, mostly single or multiple interventions, are implemented by primary-level health departments. Systematic assessment of the effectiveness of these measures is scarce. To estimate the efficacy of commonly used intervention strategies, we developed a Susceptible–Exposed–Infectious/Asymptomatic–Recovered–Water model. No intervention was predicted to result in a total attack rate (TAR) of 90% of the affected population (95% confidence interval [CI]: 86.65–92.80) and duration of outbreak (DO) of 89 days, and the use of single-intervention strategies can be futile or even counter-productive. Prophylactics and water disinfection did not improve TAR or DO. School closure for up to 3 weeks did not help but only increased DO. Isolation alone significantly increased DO. Only antibiotics treatment could shorten the DO to 35 days with TAR unaffected. We observed that these intervention effects were additive when in combined usage under most circumstances. Combined intervention “Isolation+antibiotics+prophylactics+water disinfection” was predicted to result in the lowest TAR (41.9%, 95%CI: 36.97–47.04%) and shortest DO (28 days). Our actual Shigellosis control implementation that also included school closure for 1 week, attained comparable results and the modeling produced an epidemic curve of Shigellosis highly similar to our actual outbreak data. This lends a strong support to the reality of our model that provides a possible reference for public health professionals to evaluate their strategies towards Shigellosis control.
Highlights
Shigellosis, the result of infection with Shigella, is an enteric infectious disease responsible for approximately 1,100,000 deaths per year worldwide [1]
Field epidemiological study revealed that the 2 primary routes of transmission corresponded to the 2 epidemic peaks in terms of temporal distribution, with the first peak resulting from primarily person–to-person transmission, and the second from both person– water–person and person–to-person transmission (Figure 3)
To aid in fulfilling the need for such an estimation, we developed models to estimate the effectiveness of a variety of strategies in controlling an outbreak of shigellosis, yielding findings that will be of great importance for controlling future outbreaks
Summary
Shigellosis (bacillary dysentery), the result of infection with Shigella, is an enteric infectious disease responsible for approximately 1,100,000 deaths per year worldwide [1]. In China, many private wells supplying water to schools are built in close proximity to sources of pollution, including toilets, septic tanks, sewer ditches, and lakes and ponds into which sewage is discharged As water from these wells is often not treated before being piped into schools, waterborne outbreaks of Shigella frequently occur [6], with devastating effects on students, their families, and schools. Many outbreak control strategies developed by primary-level health departments in China are empirically-driven This can be attributed to a lack of data regarding the rate of morbidity in the absence of intervention, making it difficult to estimate whether the efficacy of a single or combined intervention could be decreased if implemented using traditional methods. A bacillary dysentery model with seasonal fluctuation was formulated and studied by Bai et al [14], in which a simple Susceptible–Infectious–Recovered–Susceptible framework was employed that could not clarify the person–water–person transmission pathways
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