Epidemiology Of Infectious Diseases Flashcards
What is an infection
An infection is said to occur when micro organisms (viruses, bacteria etc) invade and multiply in the body.
What is contamination?
Contamination is the presence of a constituent, impurity or any undesirable element that spoils, corrupts, infects, makes unfit or make inferior the physical body, material, natural environment, workplace etx
What is a disease?
Disease is defined as harmful deviation from the normal structural and functional state if an organism, generally associated with signs and symptoms and different in nature from physical injury.
What’s the triad of infection?
Agent
Host
Environment
What’s an incubation period?
Incubation period is the time from initial invasion of infectious agent to onset of the disease.
What are the Determinants of incubation period?
- State of immunity of an individual
- Pathogenicity - ability of the organism to cause disease
- Microbial load
- Location - part of the body involved
Differentiate between pathogenicity and virulence
Pathogenicity is the ability of the organism to cause a disease.
Virulence is the ability of the disease to kill.
Highlight significance of incubation period
- Prognosis determination
- Quarantine
- Contact tracing
- Vaccine development
- Epidemic control - is achived when there is no new case after 2 incubation periods of the disease.
- mgt of the disease
What are the two disease with no mode of exit?
Tetanus and dracunculiasis
What are the modes of transmission?
- Direct - no vehicles
- Indirect - vehicles are used e.g food, water, vector
What’s carriership?
What are the types of carriership?
Carriership is the ability to transmit infectious agent without manifesting the disease.
Types
1. Incubatory carriership - transmit agent during incubation period. E. G Hep. B, HIV, measles
- Convalescent carriership - transmit agent after or during manifestation of the disease e.g typhoid
How do you treat a typhoid carrier?
A typhoid carrier should be treated with antibiotics for 14days.
How is a typhoid carrier treated?
A typhoid carrier should be treated with antibiotics for 14days because Salmonella typhi is stored in the urinary and gall bladders.
What’s are the ways in breaking chain of transmission?
- Increase immunity if the host.
- Reduce susceptibility
- Eliminate/reduce vehicles
- Destroy breeding site of agents.
What are the criteria for isolation?
A patient is only isolated if the disease has the following:
1. High infectivity
2. High virulence
3. No extra human reservoir
Differentiate the following epidemic, endemic, pandemic and outbreak.
EPIDEMIC: occurrence of a disease in excess of what is expected if that population at that given time.
ENDEMIC: Regular occurrence of a disease at all times in a particular place.
PANDEMIC: An epidemic across atleast two countries in 2 different continents. i.e global epidemic.
OUTBREAK: occurrence of a disease in excess of what is expected of that population over a SHORT period of time. i.e Short epidemic.
What are the types of outbreak?
Common source outbreak
Propagated source outbreak
What’s the difference between point source and continuous source?
Point source: outbreak is from the same source and at the same time. People contact it at same time
Continuous source: outbreak is from same source but at different times. They contact it at different time.
Differentiate b/w common and propagated source.
Common source: outbreak is from the same source.
Propagated: source is not the same.
What is median time on a point source outbreak curve?
The time when 50% of people manifest signs and symptoms of the disease/infection.
Who is a primary case?
The first person to bring infection (in propagated source outbreak)
Using formula, diff btw attack rate and secondary attack rate.
ATTACK RATE = no.of new cases divided by
No of susceptible persons, multiply by 100
Differentiate btw attack rate and secondary attack rate.
Attack rate is not a good measurement of spread.
In attack rate, primary case is involved.
Attack rate is useful in common source outbreak.
SAR is a good measurement of spread.
It does not include the primary case.
It is useful in propagated outbreak
Ways to reduce SAR
Immunization of people to reduce susceptibility.
Chemoprophylaxis
Outline the steps in investigation of disease outbreak
- Verify diagnosis
- Verify there is an epidemic.
- Open register for cases identified. Tools in identifying cases: spot map, epidemic curve, case control study
- Immunize control to reduce susceptibility.
- Treat all cases.
- Communicate the factors to the people.
- Write a report of the epidemic and it’s intervention.
- Surveillance.
What is surveillance?
Surveillance is continuous watchfulness of factors responsible for the spread of a disease. This is achieved through data collection
