The contagious period ends right around when you start to sound sick over the phone, which is probably evidence of cold viruses evolving to spread optimally in the workplace.

"Colds", by Randall Munroe, licensed under Creative Commons Attribution-NonCommercial 2.5 License

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The contagious period ends right around when you start to sound sick over the phone, which is probably evidence of cold viruses evolving to spread optimally in the workplace.