Surveillance of infectious diseases in animals and humans 2021

Surveillance of infectious diseases in animals and humans 2021 is the annual report describing the surveillance activities carried out in Sweden during the year. The report covers surveillance for important animal diseases and zoonotic agents in humans, food, feed and animals, carried out and compiled by experts from several Swedish governmental agencies, university and the private industry with surveillance mandates along the entire food chain, from farm to fork.This year’s report again refers to the disease situation and surveillance implemented during the ongoing COVID19 pandemic, with consequences both on surveillance efforts and their results. The report includes several chapters describing zoonotic diseases of importance to human health. Disease surveillance in humans is driven primarily by patients seeking care, i.e., passive surveillance, and fewer patients have presented to primary care with symptoms consistent with many of the common zoonoses during the pandemic. This is hypothesised to be related both to patients with these symptoms choosing to not seek care and a true reduction in disease incidence due to changes in general hygiene such as increased handwashing, physical distancing and reduced travel due to COVID-19-related recommendations.From an animal health perspective, the pandemic resulted in extensive outbreaks of SARS-CoV-2 infections in mink in 2020, with vast consequences for the international mink fur industry and potential impact on public health. In Sweden, this prompted the ban on breeding of mink during 2021 along with restrictions to reduce the risk of the transmission of SARS-CoV-2 between humans and mink. At the EU level, surveillance for the presence of SARS-CoV-2 in mink became compulsory in all member states during the year.The front cover of this year’s report shows a hen on the necropsy table at the National Veterinary Institute, SVA; this to represent the most dramatic animal health event in Sweden during the last decades. The outbreak of avian influenza that affected domestic poultry and wild birds during the 2020–2021 season is the largest ever recorded in the country, with millions of birds lost to the disease or to measures implemented to reduce the risk of further spread (see more at page 49).Following the first outbreak of Salmonella Choleraesuis in Sweden in 40 years, described in our previous report, an intensified surveillance of Salmonella in wild boar was carried out during 2021. The results from this surveillance suggest that S. Choleraesuis is widespread in parts of the country, posing a potential threat to the pig production. This is further described in the “In focus” section within the chapter on salmonellosis (page 76).These major animal health events affecting the pig and poultry industries highlight the need for strengthened biosecurity measures at farms, directed towards avoiding introduction of pathogens from the environment.The information generated by animal disease surveillance is of key importance for the declaration of the good health and welfare status of Swedish animals. Some benefits of surveillance activities are inherent, such as the prevention of animal disease and promotion of public health. However, many surveillance activities are in place primarily to ensure safe trade and movement of animals, thereby facilitating trade and giving access to foreign markets. The restrictions put in place to maintain trust between trading partners are also where the major costs appear in case of outbreaks of regulated diseases. To reinstate a favourable status, it is necessary to provide evidence in the form of highquality surveillance data that disease is once again absent from the country, region or sector, or at least under control.A lot of the information in this report is of key importance to demonstrate the good health and welfare of Swedish animals to the benefit of safe trade and access to foreign markets. As an EU member state, Sweden shares the implications and consequences of exotic disease introduction with many other European countries. We are part of a panEuropean surveillance system, where our efforts contribute, directly and indirectly, to the understanding of risks that emerging diseases pose to other EU countries. Openness, transparency and early action through preparedness are key for effective early warning and control. These are also vital factors to maintain trust and for joint European preparedness to which we actively contribute. In line with this, our understanding of the Swedish disease situation in 2021 is provided in this report.