Infectious Diseases 2023

Since mid-July 2023, an outbreak caused by highly pathogenic avian influenza A(H5N1) virus clade 2.3.4.4b genotype BB is ongoing among farmed animals in South and Central Ostrobothnia, Finland. Infections in foxes, American minks and raccoon dogs have been confirmed on 20 farms. Genetic analysis suggests introductions from wild birds scavenging for food in farm areas. Investigations point to direct transmission between animals. While no human infections have been detected, control measures are being implemented to limit spread and human exposure. As more affected farms were detected, the Ministry of Agriculture and Forestry amended the national legislation on 18 July 2023, making it possible for animal health authorities to order restrictions and culling of animals in case HPAI virus infection was detected in fur animals. Previously, this possibility only existed for poultry and captive birds. At some farms, all animals will need to be culled while in others, where the spread of the disease is limited, only animals in affected shade houses will be culled. In the latter cases, the situation will be closely monitored, to ensure the stamping out of the disease.
At present, it appears likely that transmission among fur animals is contributing to the evolution of the outbreak, and PB2 mutations associated with improved replication in mammalian cells have been detected in a subset of the fur animal cases. A well-recognised concern exists that prolonged replication of the HPAI H5N1 virus in a high-density mammalian population, such as the fur farms, might lead to viral forms that could more easily spread among humans.