(N/A) Infectious diseases spread through various modes of transmission. These include:
$a)$ Through air: When an infected person sneezes or coughs,they release droplets containing pathogens. These droplets can be inhaled by a healthy person,allowing the microbes to enter a new host.
Examples: $Common$ $cold$,$pneumonia$,and $tuberculosis$.
$b)$ Through water: Consumption of contaminated water can lead to the spread of diseases to many people.
Examples: $Cholera$,$amoebiasis$,and $hepatitis$.
$c)$ Through sexual contact: Certain diseases like $AIDS$ and $syphilis$ are transmitted through sexual contact. Additionally,the $AIDS$ virus can spread through blood transfusion,shared infected syringes,from an infected mother to her baby during pregnancy,or through breastfeeding.
$d)$ Through vectors: Some animals act as intermediaries or vectors. These vectors carry pathogens from an infected person to a healthy person.
Example: $Mosquitoes$ spread the malaria-causing organism in humans while sucking their blood.