By contrast to naturally infected birds, which were only measured once, birds of the experimental groups were measured repeatedly: an initial measurement made on average 9 days before inoculation (range: 4–16 days), a second measurement during the acute-infection stage (approx. 23 days post inoculation; range: 14–34 days) and finally, during the chronic infection stage (approx. 34 days post inoculation; range 31–41 days).