is there any discharge? is he acting lethargic?
Infectious bronchitis is a virus that will quickly go through the flock, but usually only lasts a few weeks. Most grown chickens recover from it without any treatment, but hens may lay eggs with wrinkled shells or slow down laying for a bit. Other diseases such as mycoplasma and coryza would usually have more symptoms. A vet or local extension agent could help if you want to get him tested.