Which one of the following is not a bacterial disease?

Vectors can be defined as

Raju of Class $IX$ was suffering from chickenpox. His friends Priya and Shaurya wanted to visit him. Shaurya's parents did not allow him to go. Priya had already suffered from it a few months before. Priya's parents allowed her to visit him. What could be the reason behind their parents' decision? What is the basis of the principle of immunisation?

What is the difference between a virus and a bacteria?

How can we prevent water-borne and vector-borne infections?

Vectors can be defined as: