2. Factors that Contribute to the Spread of Disease
Virulence of
pathogen
Susceptibility of
the population
Lack of
immunization
Mode of
transmission of
the pathogen
Inadequate
sanitation
procedures
3. Reservoirs of Infections
• any site where the pathogen can multiply or merely survive
until it is transferred to the host
– Human reservoir
– Animal reservoir
– Inanimate reservoir
4. • principal living reservoir of disease because
many human pathogens are specie-specific
• carrier – harbors the pathogen but have no
signs and symptoms
Human Reservoir
5. Carrier
• incubatory carrier – transmits the pathogen during
the incubation period
• convalescent carrier – transmit pathogen during
convalescence or recovery period
• active carriers – completely recovered from
disease but continue to harbor the pathogen
indefinitely
• passive carriers – carry the pathogen without ever
having the disease
6. zoonoses- infectious diseases that humans
acquire from animal sources
Routes:
• Direct contact – with infected animal or
with domestic pet waste
• Inhalation – from contaminated hides,
fur, feathers
• Ingestion – contaminated food and
water; consumption of infected animal
products
• Injection of the pathogen – insect vector
Animal reservoir
7. Inanimate (non-living) reservoir
• e.g. air, soil, food, milk, water, and fomites
• Fomites – contaminated materials
• e.g. clothing, bedding, urinals/bedpans, eating and drinking
utensils
• Air – contaminated by dust, smoke, and respiratory
secretions of humans expelled into the air by
breathing, blowing, sneezing, and coughing
9. Contact Transmission
- spread of an agent of disease by direct, indirect or
droplet transmission
• 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
10. Contact Transmission…
• Indirect Contact Transmission
• from source to a non-living object to a
susceptible host
• Droplet Transmission
• Microbe spread in droplet nuclei that travels only
a short distance (<1 meter) i.e. coughing,
sneezing.
• Laughing or talking
11. transmission of disease agent by a medium
(i.e. water,
food, air, etc)
• Waterborne Transmission
• water contamination i.e. cholera,
Shigella
• 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
Vehicle Transmission
13. Control of Epidemic Disease
• Report cases of communicable diseases to proper
agencies
• Public education
• Identification and elimination of reservoirs of
infection
• Isolated disease person
• Participate in immunization program
• Help to treat sick person
