communicable diseases chain of infection
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PowerPoint Presentation on how communicable diseases spreads through the chain of infectionTRANSCRIPT
UNDERSTANDING DISEASES
COMMUNICABLE DISEASES
Some Important Terms
MORBIDITY
• Ratio of persons infected with the disease to those who are not infected in a population
MORTALITY
• Number of death in a population
Projected causes of Death
Some Important Terms
EPIDEMIC
• “outbreak”; disease affects greater than usual number of cases in a particular region, usually occurring within a relatively short period
PANDEMIC
• Disease occurs in epidemic proportions in many countries simultaneously
The Chain of Infection
The Chain of Infection
1. Infectious Agent – PATHOGEN• Microbial organisms which has an ability to
cause a disease
a. Algae
b. Bacteria
c. Fungi
d. Protozoa
e. Viruses
Ex. Infectious disease – Dengue fever
Pathogen - Flavivirus
The Chain of Infection
Characteristics of pathogens which enables it to cause an infection:
a. Virulence – ability to grow & multiply
b. Invasiveness – ability to enter the tissue
c. Pathogenicity – ability to cause a disease
*Infection *Infection – colonization by a pathogen; when a pathogen lands or enters a person’s body & remains there
The Chain of Infection
2. Reservoir – where a microorganism normally lives & reproduces
*Carriers – *Carriers – an organism that is infected by a pathogen but does not necessarily have the infectious disease caused by that pathogen
The Chain of InfectionTypes of Carriers:
a. Passive Carrier – carries the pathogen without ever having had the disease
b. Incubatory Carrier – is capable of transmitting a pathogen during the incubation period
c. Convalescent Carrier – harbors & can transmit a particular pathogen while recovering from an infectious disease (convalescent period)
d. Active Carrier – have completely recovered from the disease but continue to harbor the pathogen indefinitely
The Chain of Infection
3. Portal of Exit• route of escape of the pathogen from
the reservoir• Body orifices (mouth, nose, anus),
secretions, skin through insect bitesEx. Flu – mucus secretions
Hepatitis A – stoolSARS – droplets from sneezing
The Chain of Infection
4. Mode of transmission• The way the pathogen gets from the
reservoir to the new hosta. Contact – indirect & directb. Airborne – pathogen stays in the air,
common air sourcec. Droplets – from sneezing, coughing; bloodd. Vehicular – contaminated inanimate
objects e. Vectors – biting insects/arachnids
Dengue Mosquito
Aedes aegypti
The Chain of Infection
5. Portal of Entry
• Route through which the pathogen enters its new host
• Body orifices, breaks in the skin (open wounds); skin through bites
6. Susceptible Host
• A person who can get sick when exposed to a disease-causing pathogen
• Humans with low immunity or resistance
The Chain of Infection
INFECTIOUS AGENT
RESER-VOIR
PORTAL
OF EXIT
MODE OF
TRANS-MISSION
PORTAL
OF ENTRY
SUSCEPTIBLE HOST
Plasmodium falciparum
(malaria)
Salmonella typhi
(typhoid fever)
Blood – liver cell
Gall bladder
Skin – mosquito bite
Rectum – feces
Vectors - mosquito
Contact
Vehicular
Skin – mosquito bite
Mouth –food
Humans especially those with low immunity
Humans exposed to contaminated sources of food