Question

give a brief account of infectious diseases how do they spread

Answer 1

the diseases that can spread from infected to healthy person are infectious diseases. e. g malaria , common cold etc.
they can spread with the help of vectors

Answer 2

diseases that can spread from an infected person to a healthy person through water, food or physical contact
diseases like chlorea and common cold
when an infected person sneezes he spread thousands of pathogens in the air through the fine droplets of moisture .when these pathogens enter the body of a healthy person on breathing in that air he may get infected
hope it will help you