Students of class $IX$ had to present a seminar on 'Dengue fever'. They wanted to introduce the disease by starting with:
$(a)$ Immediate causes of the diseases
$(b)$ Definition of infectious diseases
$(c)$ Pathogen causing dengue fever
$(d)$ Vector responsible for dengue microbe.
Can you help them to explain the above points? Give details.

(A-D) Immediate cause is the primary factor that leads to the onset of a disease. For Dengue fever,the immediate cause is the entry of the dengue virus into the human body.
$(b)$ Infectious diseases are those caused by biological agents (pathogens) that can spread from an infected person to a healthy person through mediums like air,water,food,or vectors. Examples include cholera and chickenpox.
$(c)$ The pathogen causing dengue fever is the dengue virus $(DENV)$,which belongs to the family Flaviviridae.
$(d)$ The vector responsible for transmitting the dengue virus is the female $Aedes$ $aegypti$ mosquito. The mosquito requires a blood meal to obtain proteins necessary for egg development. During the act of biting an infected person,the mosquito ingests the virus,which then replicates and is transmitted to a healthy person during subsequent bites.