Timm Harder

Institute of Diagnostic Virology, Friedrich-Loeffler-Institute, Greifswald, Germany

KEYNOTE SESSION - Healthy pigs, healthy humans

"The growing issue of influenza infections in pigs and the related zoonotic risk"
Thursday, 12th May 2022

Timm Harder, Germany, is a virologist with a veterinary background and broad interest in influenza viruses particularly of avian and porcine hosts. Study fields range from diagnostic improvements, molecular epidemiology, and pathogenicity, to applied preventive measures and regulatory issues. He is head of the national avian influenza reference laboratory at Friedrich-Loeffler-Institute, Isle of Riems, Germany. The laboratory is an active member in international networks of the World Health Organization for Animal Health (O.I.E., OFFLU) and the Food and Agriculture Organization (FAO) of the UN for research and diagnosis on animal influenza.


Swine influenza caused by influenza A viruses (IAV) directly affects respiratory health and indirectly impair reproduction rates which leads to economically tangible production losses. In Europe, the number of pigs raised has remained fairly stable over the last decade. However, production systems have intensified featuring fewer holdings but, in turn, increased breeding herd size and more piglets per litter. This seems to foster swine IAV (swIAV) infections with respect to the entrenchment within and spread between holdings in Europe.
The most recent human pandemic of 2009 has highlighted the zoonotic and reverse zoonotic potential of swIAVs. Pigs constitute a mixing vessel of influenza A viruses from different species including avian and human hosts. It should be noted that, since 1918, all human pandemic influenza viruses with the sole exception of the H2N2 virus of 1958 have been transmitted in a reverse zoonotic mode from human into swine populations. Swine populations acted as reservoirs of these viruses but also proved to be reassortment machines with IAV of other, particularly avian hosts. Pig and poultry production areas in Europe are largely overlapping. As a result, new variants of swIAV containing zoonotic components continue to be detected. This increases risks that such components might finally reassort into viruses with pandemic potential.
Disease management of swine influenza is difficult and relies on biosecurity and vaccination.
A few commercial vaccines are licensed for swIAV in Europe and all are based on inactivated, adjuvanted whole virus preparations. Recently discovered and widely proliferating forms of self-sustaining (holding-endemic) modes of swIAV infections in large swine holdings challenge these preventive concepts by generating vaccine-escape mutants in rolling circles of infection. Also in light of the COVID pandemic, an infectologically safe livestock production must be secured. This task is further complicated by conflicting goals of the producers’, citizens’ and consumers’ demands.
Here, a review of the scientific literature on zoonotic aspects of swine influenza is presented and related issues of swine production in Europe are pinpointed. Key features of future research to secure and improve pig production are introduced.