Comparison of experimental and natural infections. A - Upper left drawing - typical shedding pattern in experimental infections. Most infected cows switch between low and high shedding, while in naturally infected cows, the shedding level rapidly rise from a non-infected state to high shedding. Each color represents an individual cow. B - Upper right drawing. Distribution of switch numbers in naturally infected and experimentally infected cows. The fraction of naturally infected cows with more than 1 switch is less than 5%, while most experimental infections have more than one switch. A switch is defined as an increase followed by a decrease in the shedding level. C,D - Lower left and right panels - distribution of times to first shedding (left) and to high shedding (right) from the birth of the cow. Experimentally infected cows shed earlier and reach high shedding earlier than naturally infected cows. The values at 5000 days represent the cows that never reach high shedding.