I have 10 white leghorns. They just started laying eggs 2weeks ago. They are about 21 weeks old. Noticed some strange growths on comb.
Looked it up and they have fowlpox. So far it looks like just the dry type. Next batch of chicks, if any, will be vaccinated for this. Got to let it run its course .
2 days ago I got 7 eggs. Today I got 4. I guess I may have to start over if it gets real bad. Need to give it a couple of months.

Its common and usually not anything to get concerned over. Anywhere mosquitoes are, your chickens can get it.

Sometimes blood spots from fighting can look like fowl pox. My junglefowl hybrid games will get bloody combs that dry and scab over with black spots. The best way to tell the difference is that blood scabs are usually dark black with no grey ring. Fowlpox usually has a grey ring around the black spot.