Chilean H5N1 virus spreads fatal disease in ferrets
Highly pathogenic avian influenza A(H5N1) viruses from Clade 2.3.4.4b have triggered significant outbreaks among bird populations across five continents, with spill-over into various mammalian species. Instances of mutations linked to mammalian adaptation have sporadically surfaced in avian strains and more frequently in mammalian strains post-infection. Human infections with A(H5N1) viruses after contact with infected wildlife have been documented on multiple continents, underscoring the imperative for assessing pandemic risk associated with these viruses.
In a recent study, the pathogenicity and transmissibility of the A/Chile/25945/2023 HPAI A(H5N1) virus were examined. This novel reassortment, incorporating four gene segments (PB1, PB2, NP, MP) from the North American lineage, was isolated from a severe human case in Chile.
In vitro evaluations and experiments using the ferret model revealed that this virus exhibited a notable capacity to induce fatal disease, marked by high morbidity and dissemination beyond the lungs in virus-inoculated ferrets. While the virus could transmit to naïve contacts under direct contact conditions, resulting in similarly severe disease in contact animals, it did not demonstrate productive transmission in respiratory droplet or fomite transmission models. These findings suggest that for this virus to potentially trigger a pandemic, it would need to acquire a transmissible airborne phenotype in mammals.
