Protecting Sewer and Wastewater Workers from Ebola Risks

Protecting Sewer and Wastewater Workers from Ebola Risks and Other Emerging Pathogens Water and Health Conference, UNC Joseph Zabinski Kelsey Pieper Jacqueline Mac. Donald Gibson October 28, 2015

Ebola in the U. S. Source: New York Times Background BBNs Model Next Steps 2

Why model risks in wastewater? • Ebola virus’ persistence in wastewater systems is not well-understood • accurately characterizing risk can help utilities target interventions • wastewater treatment workers benefit from clearer understanding of job hazards Background BBNs Model Next Steps 3

Issues with Risk Characterization • • behavior of Ebola in wastewater (WW) survival outside body fluids Africa ≠ U. S. differences in WW treatment systems How do we model Ebola risk in WW systems with heterogeneous, incomplete data? Background BBNs Model Next Steps 4

Solution: BBN Modeling • Bayesian belief network (BBN) approach • statistical modeling technique that allows for the incorporation of different data sets • can handle imperfect and incomplete data • shows ‘two-way’ relationships Bayes’ Formula: Background BBNs Model Next Steps 5

Bayesian Beliefs If I see that it’s raining outside, I know that Kelsey probably brought her umbrella… Background BBNs Model Next Steps 6

Bayesian Beliefs …and if I see that she brought her umbrella, I know it’s probably raining. Background BBNs Model Next Steps 7

Bayesian Beliefs Background BBNs Model Next Steps 8

Ebola Modeling Concept dilution • • • hospital discharge stormwater flow inputs inactivation • • • temperature time outside body treatment Background BBNs dose-response Model Next Steps 9

Model Caveats • very conservative in assumptions • some data still needs to be confirmed with stakeholders (especially utilities) • dose-response model is preliminary and based on primate studies • no incorporation (yet!) of PPE risk mitigation • infectious dose ~1 viral particle/m. L Background BBNs Model Next Steps 10

WW Worker Risk Model Disclaimer: draft model still under development Background BBNs Model Next Steps 11

WW Worker Risk Model disease hospital climate Disclaimer: draft model still under development WWTM Background BBNs Model Next Steps 12

Disease State disease hospital climate Disclaimer: draft model still under development WWTM Background BBNs Model Next Steps 13

Disease State disease hospital climate Sources: Wolf et al. , 2015 Bishop et al. , 2014 Chertow et al. , 2014 Lowe et al. , 2014 WWTM Background BBNs Model Next Steps 14

Viral Attenuation disease hospital climate Disclaimer: draft model still under development WWTM Background BBNs Model Next Steps 15

Viral Attenuation disease hospital climate Disclaimer: draft model still under development WWTM Background BBNs Model Next Steps 16

Viral Attenuation disease hospital climate WWTM Background BBNs Model Next Steps 17

Viral Dilution disease hospital climate Disclaimer: draft model still under development WWTM Background BBNs Model Next Steps 18

Viral Dilution disease hospital climate WWTM Background BBNs Model Next Steps 19

Viral Dilution disease hospital climate WWTM Background Source: CDC hospital survey, 2011 BBNs Model Next Steps 20

Final Step: Dose Response Disclaimer: draft model still under development 21

Low Danger Disclaimer: draft model still under development 22

High Danger Disclaimer: draft model still under development 23

Next Steps • confirm data for treatment nodes • work with utilities to understand data inputs (worker distance from hospital, in-system dilution, etc. ) • incorporate PPE and exposure routes • finalize dose-response • manage conservatism • develop user interface Background BBNs Model Next Steps 24

Thanks! Joseph Zabinski zabinski@unc. edu 25