Intensified environmental surveillance supporting the response to wild poliovirus type 1 silent circulation in Israel, 2013

Abstract

An emergency response was triggered by recovery of wild poliovirus type 1 (WPV1) of the South Asia (SOAS) lineage from sewage in southern Israel in April 2013 during routine environmental surveillance. Public health risk assessment necessitated intensification of environmental surveillance in order to facilitate countrywide monitoring of WPV1-SOAS circulation. This involved increasing sampling frequency and broadening the geographical area, for better coverage of the population at risk, as well as modifying sewage testing algorithms to accommodate a newly developed WPV1-SOAS-specific quantitative real-time RT-PCR assay for screening of RNA extracted directly from sewage concentrates, in addition to standard virus isolation. Intensified surveillance in 74 sites across Israel between 1 February and 31 August 2013 documented a sustained high viral load of WPV1-SOAS in sewage samples from six Bedouin settlements and two cities with Jewish and Arab populations in the South district. Lower viral loads and intermittent detection were documented in sampling sites representing 14 mixed communities in three of the five health districts in central and northern Israel. Environmental surveillance plays a fundamental role in routine monitoring of WPV circulation in polio-free countries. The rapid assay specific for the circulating strain facilitated implementation of intensified surveillance and informed the public health response and decision-making.

Laboratory Surveillance of Polio and Other Enteroviruses in High-Risk Populations and Environmental Samples

“…Intensified environmental (sewage) surveillance in Israel succeeded in identifying the introduction and sustained silent spread of WPV1, in 2013 which had circulated among a highly immune population (12,13). Importations of WPV to Switzerland from Chad in 2007 and to Egypt from Pakistan in 2013 were also identified through environmental surveillance (31,32).…”

“…This is based on the observation that infected people, including those who are asymptomatic, shed large amounts of virus into the wastewater system, making this type of detection effective (10,11). That was the case in Israel in 2013 where silent introduction and circulation of WPV type 1 (WPV1) occurred in a highly immune population in which an inactivated polio vaccine (IPV) had been used exclusively since 2005, and AFP surveillance alone had not detected it because viral shedding was not accompanied by any paralytic symptoms (12,13). As the GPEI moves toward achieving the goal of PV eradication, environmental surveillance might also play a significant role in providing evidence for certification of polio-free status (11).…”

Hepatitis E Virus Genotype 3 in Sewage and Genotype 1 in Acute Hepatitis Cases, Israel

“…In Israel, a national program for surveillance of the poliovirus in sewage has been ongoing since 1988, and facilitated identification of wild poliovirus in 2013 that activated a major emergency response by the Public Health Services. 3 Unlike the ongoing surveillance for polio, there is no HEV monitoring in Israel. The overall prevalence of anti-HEV IgG antibodies in Israel was recently found to be 10.6%, 4 but in a study that retrospectively assessed acute HEV infections in Israel between 1993 and 2013, only 68 HEV positive cases were identified (∼3 per year).…”

Is Italian population protected from Poliovirus? Results of a seroprevalence survey in Florence, Italy

“…The reintroduction and wide circulation in the population of WPV1 was detected by environmental surveillance at sewage treatment plants but no clinical cases were signaled. 12 The second issue is a continuing surveillance of flaccid paralysis in order to identify unexpected diseases due to wild or vaccine-derived polioviruses.…”