Four countries reported new polio cases this week, according to the latest update from the Global Polio Eradication Initiative (GPEI).
Afghanistan and Pakistan each recorded wild poliovirus type 1 (WPV1) cases. The WPV1 case in Afghanistan was in Badghis province, and it marks the country's first WPV1 case of 2025. The two WPV1 cases reported in Pakistan were in Sindh province, with paralysis onset on December 15, 2024, and January 30. Pakistan has now reported 74 WPV1 cases for 2024 and 2 for 2025.
Algeria reported a case of circulating vaccine-derived poliovirus type 2 (cVDPV2) from Adrar province, with paralysis onset on December 10, 2024. It's the country's first cVDPV2 case of 2024. Guinea reported a vaccine-derived poliovirus type 3 (cVDVP3) case in Kankan province with paralysis onset on November 21, 2024, bringing its 2024 total to four cVDPV3 cases.
GPEI also noted the identification of three cVDPV2-positive environmental samples in Gaza, where a mass polio vaccination program is set to begin this weekend.
'Exceptionally rare' mutation on H5N1 virus in Canada tied to antiviral drug resistance
In a research letter published this week in Emerging Microbes & Infections, researchers at the Canada Food Inspection Agency (CFIA) describe their discovery of a mutated H5N1 avian flu strain resistant to the antiviral drug oseltamivir (Tamiflu) on eight chicken farms in British Columbia in October 2024.
When investigating a widespread and ongoing H5N1 outbreak at 45 poultry farms, the CFIA National Centre for Foreign Animal Disease team sequenced the virus, identifying it as a clade 2.3.4.4b A(H5N1) strain. The virus had a neuraminidase surface protein derived from a low-pathogenic flu virus from a North American lineage.
Despite evidence to suggest this substitution reduces viral fitness, viruses harboring this substitution spread rapidly across 8 farms in the 15 days following its initial detection.
"Isolates from 8 farms reveal a mutation in the neuraminidase protein (H275Y) that is exceptionally rare among clade 2.3.4.4b viruses (present in 0.045% of publicly available clade 2.3.4.4b isolates)," the researchers wrote. "NA-H275Y is a well-known marker of resistance to the neuraminidase inhibitor oseltamivir."
The virus likely emerged in Canada in September 2024, the authors said. The US Department of Agriculture later updated its North American A(H5N1) genotyping tool GenoFlu to designate the virus as genotype D1.1.
"Despite evidence to suggest this substitution reduces viral fitness, viruses harboring this substitution spread rapidly across 8 farms in the 15 days following its initial detection," the researchers wrote. "As oseltamivir is the most widely used therapeutic and prophylactic against IAV [influenza A virus], the continued circulation of viruses harboring NA-H275Y may necessitate a re-evaluation of influenza treatment strategies in Canada."
It's unclear whether the mutated virus is still circulating.
Four more H5N1 detections in US
Yesterday, the US Department of Agriculture Animal and Plant Health Inspection Service confirmed four more highly pathogenic avian flu detections, including a commercial turkey farm in Sac County, Iowa, affecting nearly 30,000 birds and three backyard flocks in Maine and Pennsylvania totaling nearly 500 birds.
In the last 30 days, 101 commercial and 55 backyard flocks have been infected, at a loss of 21.7 million birds.
