Estimation of polio infection prevalence from environmental surveillance data

Science Translational Medicine
29 March 2017 Vol 9, Issue 383

Estimation of polio infection prevalence from environmental surveillance data
By Yakir Berchenko, Yossi Manor, Laurence S. Freedman, Ehud Kaliner, Itamar Grotto, Ella Mendelson, Amit Huppert
Science Translational Medicine29 Mar 2017 Restricted Access
Close monitoring of virus shed into sewage systems allows quantitative surveillance of a polio outbreak
Keeping an eye on polio
As the eyes are a mirror of the soul, a city’s sewage is a reflection of its people’s health. Berchenko et al. take advantage of a natural experiment in southern Israel to quantify this relationship for polio. By measuring virus shed into sewage waste in cities in which a known number of people received a live polio vaccine, the authors created tools that can be used to monitor polio incidence in other cities. Thus, virus levels in sewage waste can give an early warning of the reappearance of viral disease or verify its absence.
A major obstacle to eradicating polio is that poliovirus from endemic countries can be reintroduced to polio-free countries. Environmental surveillance (ES) can detect poliovirus from sewage or wastewaters samples, even in the absence of patients with paralysis. ES is underused, in part because its sensitivity is unknown. We used two unique data sets collected during a natural experiment provided by the 2013 polio outbreak in Israel: ES data from different locations and records of supplemental immunization with the live vaccine. Data from the intersecting population between the two data sets (covering more than 63,000 people) yielded a dose-dependent relationship between the number of poliovirus shedders and the amount of poliovirus in sewage. Using a mixed-effects linear regression analysis of these data, we developed several quantitative tools, such as (i) ascertainment of the number of infected individuals from ES data for application during future epidemics elsewhere, (ii) evaluation of the sensitivity of ES, and (iii) determination of the confidence level of the termination of poliovirus circulation after an outbreak. These results will be valuable in monitoring future outbreaks with ES, and this approach could be used to certify poliovirus elimination or to validate the need for more containment efforts.