The role of supplementary environmental surveillance to complement acute flaccid paralysis surveillance for wild poliovirus in Pakistan-2011-2013

• Authors: Tori L. Cowger, Emory University; Cara C. Burns, Centers for Disease Control and Prevention; Salmaan Sharif, National Institute of Health Research; Howard E. Gary, Centers for Disease Control and Prevention; Jane Iber, Centers for Disease Control and Prevention; Elizabeth Henderson, Centers for Disease Control and Prevention; Farzana Malik, National Institute of Health Research; Syed Sohail Zahoor Zaidi, National Institute of Health Research; Shahzad Shaukat, National Institute of Health Research; Lubna Rehman, National Institute of Health Research; Mark A. Pallansch, Centers for Disease Control and Prevention; Walter Orenstein, Emory University
• Journal Title: PLoS ONE
• Volume: Volume 12, Number 7
• Publisher: Public Library of Science | 2017-07-25, Pages e0180608-e0180608
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pone.0180608
• Subjects: Biology, Virology; Health Sciences, Public Health; Health Sciences, Immunology
• Keywords: Science & Technology; Multidisciplinary Sciences; Science & Technology - Other Topics; VACCINE-DERIVED POLIOVIRUSES; ERADICATION; CIRCULATION; PROGRESS; EGYPT; POLIOMYELITIS; TRANSMISSION; OUTBREAK; PAKISTAN; SEWAGE; Poliovirus; Viral packaging; Nucleotide sequencing; Disease surveillance; DNA sequence analysis; Infectious disease surveillance

Abstract

Background: More than 99% of poliovirus infections are non-paralytic and therefore, not detected by acute flaccid paralysis (AFP) surveillance. Environmental surveillance (ES) can detect circulating polioviruses from sewage without relying on clinical presentation. With extensive ES and continued circulation of polioviruses, Pakistan presents a unique opportunity to quantify the impact of ES as a supplement to AFP surveillance on overall completeness and timeliness of poliovirus detection. Methods: Genetic, geographic and temporal data were obtained for all wild poliovirus (WPV) isolates detected in Pakistan from January 2011 through December 2013. We used viral genetics to assess gaps in AFP surveillance and ES as measured by detection of ‘orphan viruses’ (1.5% different in VP1 capsid nucleotide sequence). We compared preceding detection of closely related circulating isolates (99% identity) detected by AFP surveillance or ES to determine which surveillance system first detected circulation before the presentation of each polio case. Findings: A total of 1,127 WPV isolates were detected by AFP surveillance and ES in Pakistan from 2011–2013. AFP surveillance and ES combined exhibited fewer gaps (i.e., % orphan viruses) in detection than AFP surveillance alone (3.3% vs. 7.7%, respectively). ES detected circulation before AFP surveillance in nearly 60% of polio cases (200 of 346). For polio cases reported from provinces conducting ES, ES detected circulation nearly four months sooner on average (117.6 days) than did AFP surveillance. Interpretation: Our findings suggest ES in Pakistan is providing earlier, more sensitive detection of wild polioviruses than AFP surveillance alone. Overall, targeted ES through strategic selection of sites has important implications in the eradication endgame strategy.