All wild animals carry diseases.
In some cases these might be of concern because they can spread to humans or domestic animals. In other cases they may be of interest simply because the signs of the disease have been seen and you want to know more. Though diseases are relatively common in these animals there is usually an increase in reporting when the hare populations are at a peak. High populations mean that there is an increased chance of one animal infecting another. In addition, when there are too many animals in one area, the amount of available food is reduced so that the animals become weaker and more vulnerable to disease.