Why are we normally advised to take bland and nourishing food when we are sick?

The role of an active immune system is:

$(a)$ What are the two ways by which an infectious disease can be treated?
$(b)$ Explain the mode of action of antibiotics.

Under which of the following conditions is a person most likely to fall sick?
$(a)$ When she is recovering from malaria.
$(b)$ When she has recovered from malaria and is taking care of someone suffering from chicken-pox.
$(c)$ When she is on a four-day fast after recovering from malaria and is taking care of someone suffering from chicken-pox.
Why?

$(a)$ Which part of the body is infected by the malaria-causing microbe?
$(b)$ What are the two ways to treat an infectious disease?

Many vaccines form the public health programme of childhood immunisation for preventing infectious diseases. Name any two such diseases.