L3 Flashcards
Koch’s postulates
- The same pathogen must be present in every case of disease
- The pathogen must be isolated from the host and grow in pure culture
- The pathogen from the culture must cause the disease when it invade into a healthy body
- The pathogen must be isolated from the inoculated animal and must be a original organism
Classifying infectious diseases
Communicable disease
Infected person transmit infectious agent to another direct or indirectly
(Chicken pox, influenza)
Contagious disease
Very communicable
Non communicable disease
Not spreading from one host to another
Only cause illness when introduced in the body
Frequency of case ( sporadic to pandemic)
Sporadic
Occurs occasionally
Endemic
Constantly present in a population
Outbreak
A small number of person caught in a short period
Epidemic
Many people in a short time
Pandemic
Worldwide
Distribution of pathogens
Local infections
Small area in body
Systemic infection
Spread throughout the body
Primary infection
Initial infection
Secondary infection
Cause opportunistic infection after primary infection
Pattern of disease
Incubation period
Between initial infection and symptoms onset
Prodromal period
Appears first symptoms
Period of illness
Peak stage
Period of decline
S/s decline
Period of convalescence
Recovery
- Incubation period: infection
- Latent period: infection to onset
- Infectious period: infected pp is infectious
Chain of infection
- Infectious agent
- Reservoir
- Portal of exit
- Mode of transmission
- Portal of entry
- Suseptible host
Chain of infection
Infectious agent:
Pathogen like bacteria, viruses, fungi, parasites
Reservoir:
Place the pathogens live / grow / reproduce eg water / human
Portal of exit:
The way pathogen escape from the reservoir
Excretion/ blood / secretion
Mode of transmission
Way for pathogen to spread from infectious person
Portal of entry
Way for pathogen to enter a new host
Susceptible host
Individuals who could be infected
Breaking the chain of infection
Infectious agent: eliminate by sterilisation
Reservoir: elimnate by removing stilled water / pest control
Portal of exit
Mode of transmission: prevent by PPE
Portal of entry
Susceptible host: vaccination
Mode of transmissions DDAVV
Direct contact transmission
No intermediate object is involved
(Touching / kissing -) rabies, staphylococcus)
Droplet transmission
Distance travelled depends on size of droplet, velocity
Cough, sneeze (pneumonia)
Airborne transmission
Droplet nuclei
Small so could be prolonged
Vehicle transmission
Inanimated object (food / water / blood)
Vector transmission
Animated object ( flies)
Healthcare-associated infections
Microbe / chain of transmission / weakened host
Common health-associated infections
Pneumonia
Urinary tract infection
Surgical site infections
Blood stream infections
Control of HAI
Standard precaution
Transmission-based precaution
1. Contact precaution
2. Droplet precaution
3. Airborne precaution
Emerging infectious disease
Zika
Ebola
Middle East respiratory syndrome
Factors of emerging infectious disease
New strain
Inappropriate use of antibiotics
global warming ( surviving rate of disease)
