In the months of March and October, of each year large migrations of birds on all continents take place.

In March the birds migrate northward in search of milder temperatures and longer hours of sunshine, to reproduce. In October the birds travel to south for the winter. Often these migrations are accompanied by an increase in the presentation of infectious bronchitis in poultry farms in migratory routes. Although most strains affect the upper respiratory system, sometimes infections occur by nephropathogenic strains (causing nephritis and visceral gout) or prone to the reproductive system (especially in the oviduct resulting hidrosalpingitis). On the picture conjunctivitis and feverish produced by a strain of upper respiratory system can be observed.