Routes of Transmission

Direct transmission occurs when the pathogen is passed directly from the infected individual to a susceptible individual.
This can happen through physical contact, such as touching, biting, kissing, or sexual contact.
Direct transmission also includes vertical transmission, where the pathogen is transferred from a mother to offspring, for example, during birth or through breast milk.

Indirect transmission occurs when the pathogen is not directly transferred from the infected to the susceptible individual but involves an intermediate.
It can take place via fomites, which are inanimate objects that can carry pathogens, such as feeding utensils, bedding, or grooming tools.
Indirect transmission also involves vectors, which are organisms that transmit pathogens, such as insects. They can transmit the pathogen either passively, on their body, or actively, via a bite.
Airborne transmission, a type of indirect transmission, occurs when pathogens travel more than one metre through the air, for example in dust or on small respiratory droplets, to reach a new host.

Vehicle transmission is the spread of pathogens through a common source, such as food, water, or air.
Disease spread in this way can cause outbreaks, where a large number of individuals in the same area are infected.
To prevent vehicle transmission, control measures such as cleanliness and hygiene, safe food handling, and water treatment are crucial.

Vector-borne transmission occurs when an organism, often an insect, transmits the pathogen from one host to another.
Vectors can transmit pathogens passively, on their body, or actively, injecting it into the host, usually via biting.
Common vector-borne diseases include Lyme disease (spread by ticks) and malaria (spread by mosquitoes).
Prevention of vector-borne diseases often involves controlling or avoiding vectors.

Zoonotic transmission is of special relevance in animal management. This occurs when diseases are passed from animals to humans.
These diseases are called zoonoses and can be caused by a range of pathogens, including bacteria, viruses, and parasites.
Examples include rabies, transmitted through the bites of infected animals, and avian influenza, transmitted from birds to humans.