I'd be careful with that - in the past there were no "mega-chicken-factories" that you'd find nowadays. So you can't quite compare spread of viruses in chicken

I'd be careful with that - in the past there were no "mega-chicken-factories" that you'd find nowadays. So you can't quite compare spread of viruses in chicken today with the last "thousands of years" without very large asterisks Edit: stetrain phrased it better :)