Two days before Christmas, Canada reported vaccine-derived poliovirus type 2 (VDPV2) from two wastewater samples to the World Health Organization (WHO), the WHO's Pan American Health Organization (PAHO) said in a Dec 30 epidemiologic update.
The Canadian samples that tested positive for the virus were collected in August as part of sampling targeted to areas with close connections to communities in New York where similar wastewater positive samples were found earlier. A third positive environmental sample from Canada, also collected in August, is pending confirmation by virus isolation.
PAHO said the US Centers for Disease Control and Prevention (CDC) is testing the Canadian samples to see if they are genetically related to VDPV2 samples from New York.
Canada did not report any acute flaccid paralysis (AFP) cases in 2022.
Wastewater sampling in US
Last summer, VDPV2 was confirmed in a young unvaccinated man without recent travel in New York's Rockland County who experienced AFP. The case marked the United States' first since 2013.
Expanded wastewater sampling in the wake of the case has identified the virus in several nearby counties, including in New York City, suggesting community spread of the virus. As of Dec 30, New York has identified 99 positive samples of concern, 92 of them with genetic links to Rockland County's AFP case. The most recent positive sample was reported in November from Orange County.
In 2022, similar environmental findings were reported from wastewater testing in London and Jerusalem. In early December, the CDC announced that a plan to expand wastewater testing for poliovirus to assess the extent of spread and focus vaccination efforts, starting with Michigan and Philadelphia.