Active Surveillance of Influenza Virus Zoonotic Transmission Events: a Pilot Study in Belgium

The project aims at implementing a more pro-active surveillance of potential transmission of influenza viruses to humans (zoonotic transmission). Clinical surveillance of influenza in humans and avian species is well organized and has been operating for decades, but currently there is no pro-active systematic surveillance of potential transmission of animal (avian or swine) influenza viruses to humans, only follow-up of people showing clinical symptoms. People working with potentially infected animals have the highest risk. Moreover, they can represent the first steps in a pandemic: if the virus adapts to humans, infected workers could potentially spread the virus to other people.

Currently, highly pathogenic clade2.3.4.4b H5 avian influenza viruses are continuously circulating in wild birds in Belgium and the number of introduction in poultry farms has raised, increasing the contact opportunities with high viral concentrations. Several reports of suspected human infection have been made by different countries. In addition, the virus was detected in sick non-human mammals. The large circulation in wild birds thus represents an increase risk of spill-over to mammalian species, including humans, (by contact directly with wild birds, or via outbreaks in poultry). This increased opportunity for accidental spillover to new host species increases the chances for the avian virus to adapt to mammals, including humans.

Likewise, there have also been an increased number of human cases of swine influenza reported by several European countries. A pro-active surveillance aiming at also detecting asymptomatic infections would allow an early detection of transmission that could help to prevent a new pandemic.

As a piloting approach during this specific project, some dedicated sentinel networks among at-risk workers will be initiated: people in poultry farms involved with the management of outbreaks of highly pathogenic avian influenza; people working at bird (or more generally wild life) rehabilitation centres or poultry farms; veterinarians working in pig farms/slaughterhouses.