As time went by, I often heard him sniff.
After John's reports from NY studio, there was awkward silence. This might be because there was a time lag, or because he did not want to concentrate on less important news from "Bulletin" or "the Shot." Such reactions must have been very frustrating for John, who has been taking Anderson's place and doing pretty good jobs for his program.
Seeing these facts, it is obvious that he contracted cold during this report.