MLSP111: WEEK 9

Vehicles

- may indirectly transmit an infectious agent include food, water, biologic products (blood), and fomites (inanimate objects such as handkerchiefs, bedding, or surgical scalpels).

- Virulence of pathogen - Susceptibility of the population - Lack of immunization - Inadequate sanitation procedures - Mode of transmission of the pathogen

Factors that Contribute to the Spread of Disease

Human Reservoir

Many common infectious diseases have human reservoirs. Principal living reservoir of disease because many human pathogens are specie-specific

Reservoirs of Infections

The reservoir of an infectious agent is the habitat in which the agent normally lives, grows, and multiplies. The reservoir may or may not be the source from which an agent is transferred to a host.

Vector Transmission

animals that carry pathogens from one host to another

Passive carriers

carry the pathogen without ever having the disease

Active carriers

completely recovered from disease but continue to harbor the pathogen indefinitely

Air

contaminated by dust, smoke, and respiratory secretions of humans expelled into the air by breathing, blowing, sneezing, and coughing

Ingestion

contaminated food and water; consumption of infected animal products

Fomites

contaminated materials e.g. clothing, bedding, urinals/bedpans, eating and drinking utensils

Inanimate (non-living) reservoir

e.g. air, soil, food, milk, water, and fomites

Inhalation

from contaminated hides, fur, feathers

• Indirect Contact Transmission

from source to a non-living object to a susceptible host

Carrier

harbors the pathogen but have no signs and symptoms

Zoonoses

infectious diseases that humans acquire from animal sources

Injection of the pathogen

insect vector

EPIDEMIOLOGY

is the study and analysis of the distribution, patterns and determinants of health and disease conditions in defined population.

Airborne transmission

occurs when infectious agents are carried by dust or droplet nuclei suspended in air

Foodborne Transmission

raw of poorly preserved or prepared food

Airborne Transmission

spread of agents of infection by droplet nuclei in dust that travel > 1 meter from the reservoir to host

Contact Transmission

spread of an agent of disease by Direct & Indirect

Vectors

such as mosquitoes, fleas, and ticks may carry an infectious agent through purely mechanical means or may support growth or changes in the agent

Vehicle Transmission

transmission of disease agent by a medium (i.e. water, food, air, etc)

Convalescent carrier

transmit pathogen during convalescence or recovery period

Incubatory carrier

transmits the pathogen during the incubation period

Waterborne Transmission

water contamination i.e. cholera, Shigella

Direct contact

with infected animal or with domestic pet waste

Droplet Transmission

• Microbe spread in droplet nuclei that travels only a short distance (<1 meter) i.e. coughing, sneezing. • Laughing or talking

Direct Contact Transmission

• person to person transmission of an agent by • physical contact (source to susceptible host) • no intermediate host involved i.e. touching, • kissing, sexual intercourse