Field study of fecal excretion as a decision support tool in response to silent reintroduction of wild-type poliovirus 1 into Israel.

Moran-Gilad J1, Mendelson E2, Burns CC3, Bassal R4, Gdalevich M5, Sofer D6, Oberste MS3, Shulman LM2, Kaliner E7, Hindiye M6, Mor O6, Shahar L5, Iber J3, Yishay R8, Manor J6, Lev B9, Gamzu R10, Grotto I11.

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Abstract

BACKGROUND:

Israel has used an inactivated polio vaccine (IPV)-only schedule since 2005 (95% coverage). Silent reintroduction of wild type poliovirus 1 (WPV1) into Israel in early 2013 was detected in Southern Israel via routine environmental surveillance without clinical cases.

OBJECTIVES:

To estimate the rate of WPV1 excretion by age and residence and inform decision-making regarding supplemental immunization with OPV.

STUDY DESIGN:

A convenience sample of Bedouin and Jewish residential areas in the epicenter of the incident, focusing on under 8 year-olds who not previously given OPV. Fecal samples were directly tested for WPV1 RNA using a novel qRT-PCR assay. Positive samples were confirmed by gold standard cell culture and subject to genotyping.

RESULTS:

Overall, 2196 non-duplicate fecal samples were collected and analyzed. WPV1 was detected in 61 samples (2.8%), 55 of which (90.2%) were from Bedouins. WPV1 excretion rates were 5.4% among Bedouins and 0.6% among Jewish individuals. Respective age-specific rates among Bedouin and Jewish children were 4.9% and 0.2% for 0-2 years and 7.2% and 1.7% for 2-8 years. Molecular testing had 89.5% sensitivity (higher than culture) and 100% specificity.

CONCLUSION:

The rapid performance of a field study to evaluate WPV1 excretion unequivocally demonstrated substantial WPV1 infection rates among children under 8 years in Southern Israel, thus informing the decision to vaccinate this age group with bOPV and risk communication to both healthcare personnel and the public. Rapid development and implementation of molecular screening can thus underpin risk assessment and management in complex epidemiological situations.