Rapportage Varkensinfluenza surveillance 2024-2025

Since 2022, RIVM has been investigating which swine influenza viruses are present at Dutch pig farms and whether they mutate over time. Influenza viruses that affect pigs resemble the influenza viruses that affect humans. As a consequence, pigs can become infected with human influenza viruses and vice versa. In addition to swine influenza viruses and human influenza viruses, pigs can become infected with avian influenza (bird flu) viruses. This is why pigs are considered virus ‘mixing vessels’. Once a pig has become infected with both a swine influenza virus and a human or avian influenza virus, a new virus may arise. While the chances of that happening are small, a new virus that could easily infect humans and be transmitted between them could result in an influenza outbreak among humans. It is therefore good to know which influenza viruses are present at pig farms – for the benefit of both pigs and humans. In the studies conducted for this report, RIVM compared swine influenza viruses with human and avian influenza viruses. Although the swine influenza viruses have mutated somewhat over the years, they have not mixed with other influenza viruses. Moreover, it has been demonstrated that drugs against swine viruses are effective. This information is key to the successful treatment of swine influenza infections in humans. Knowledge about swine influenza will also help to create better vaccines in the future, for both humans and pigs. RIVM recommends repeating the studies for this report in the years ahead. Swine influenza viruses will not go away and are susceptible to mutation. This makes it important to monitor closely whether these viruses mix with others, thereby creating new variants. Monitoring of human and avian influenza viruses is already in place. This report was commissioned by the Ministry of Health, Welfare and Sport. It was prepared by RIVM in partnership with Royal GD, Erasmus Medical Center (EMC) and Wageningen Bioveterinary Research (WBVR).