Zoonotic potential of HPAI H5N1 viruses
Researchers from the Netherlands investigated different H5N1 isolates from Red Foxes found positive for HPAI virus. Three wild red foxes (Vulpes vulpes) were submitted with neurological symptoms (likely due to the foxes feeding on infected birds) between December of 2021 and February of 2022. Histopathological analysis demonstrated that the virus was mainly present in the brain, with limited or no detection in the respiratory tract or other organs. Limited or no virus shedding was observed in throat and rectal swabs.
Phylogenetic analysis showed that the three fox viruses were not closely related, but they were related to HPAI H5N1 clade 2.3.4.4b viruses that are found in wild birds. This suggests that the virus was not transmitted between the foxes.
Although HPAI is a respiratory virus, in these foxes, the viruses were mostly detected in the brain. Two viruses isolated from the foxes contained a mutation that is associated with adaptation to mammals. This study showed that the mutant virus replicates better in mammalian cells than in avian cells and at the lower body temperature of mammals. More mutations are required before viruses can transmit between mammals or can be transmitted to humans. However, infections in mammalian species should be closely monitored to swiftly detect mutations that may increase the zoonotic potential of HPAI H5N1 viruses, as these may threaten public health.
