C# Class constructor default value question

I have the following class:

public class Topic
    {
        public string Topic { get; set; }
        public string Description { get; set; }
        public int Count { get; set; }
    }

I would like to have the Count always set to zero when the class is created with the following:

var abc = new Topic {
  Topic = "test1",
  Description = "description1"
}

I am a bit confused with constructor. Is this possible or do I need to specify Topic, Description and Count when I create abc?