Is Food Poisiong Point source Epidemic or Continuous

Epidemic

Definition:

Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.

Types Of Epidemic:

A. Common Source epidemic.

Origin of an epidemic is a common source
For example, water poisoning.
Only those people who drink infected water from a particular water supply will develop the disease.
Hence, all patient would have a common source.
Common source epidemic is further divided into two types:

It is also known as "single exposure epidemic".
In this case, the time of exposure is brief and essentially simultaneous
All the resultant cases develop the disease within the incubation period of disease at the same time.
Epidemic curve, in this case, shows a sharp peak and sharp decline.
Clustering of cases' in a narrow interval of time All cases develop within one incubation period' of the diseasesExamples: Food poisoning, Measles, Chickenpoxholera, BHOPAL GAS TRAGEDY

In this case, epidemic reaches a sharp peak but tails off gradually over a longer period of time although the sharp peak is attained after a longer time than a point source epidemic.
This occurs because of prolonged and repeated exposures or when the source of infection is not eliminated.
Fall in no. of cases is interrupted by'Secondary wave/ Peaks
Examples: Contaminated well in a village nationally distributed brand vaccine or food, a prostitute in a gonorrhoea outbreak, LEGIONNAIRE'S DISEASE outbreak in Philadelphia (1975)
For example, a prostitute may be a common source in a gonorrhoea outbreak but in this case, epidemic curve will rise gradually as she infects her clients over a period of time. But in case of waterborne cholera, the epidemic curve reaches a sharp peak but tails of gradually. These are the two different models of common source continuous epidemic.

B. Propagated Epidemic.

A propagated epidemic occurs due to transmission of the infectious agent either
Person to Person
Through Vectors (insects etc)
Through animal reservoir
An infected person can transfer the infection to other healthy person and make him infectious as well and then he can further transmit the infection to other persons by various means (direct contact, sexual contact, through vectors, etc).
The disease remain in the community until susceptible and unimmunized individuals are present.
The epidemic starts to terminate when susceptible individuals decrease in number or the people develop immunity against the disease. Herd immunity plays special role in this case.
The epidemic curve shows gradual rise and tails of over a much longer time as compared to common source repeated exposure epidemic.
Examples: HIV, tuberculosis

Steps for Investigation of Epidemic :

Verification of diagnosis :
Is the first step in investigation of an epidemic '
Confirmation of existence of an epidemic:
Compare with disease frequencies during same period in previous years
Epidemic threshold: An arbitrary limit of '2 standard errors from the endemic occurrence'

Defining the population at risk:

Rapid search for all cases and their characteristics:

Medical survey
Epidemiological case sheet
Searching for more cases: Search for new cases is carried out every day, till the area is declared free of epidemic; this period is usually taken as 'twice the incubation period of the disease since the occurrence of last case'

Data analysis:

Exam Question

Definition:

Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area.

Types Of Epidemic:
A. Common Source epidemic.

Point source epidemic:

It is also known as "single exposure epidemic".
All the resultant cases develop the disease within the incubation period of disease at the same time.
Epidemic curve, in this case, shows a sharp peak and sharp decline.
Clustering of cases' in a narrow interval of time All cases develop within one incubation period' of the diseasesExamples: Food poisoning, Measles, Chickenpoxholera, BHOPAL GAS TRAGEDY

Common source, continuous or repeated exposure.

In this case, epidemic reaches a sharp peak but tails off gradually over a longer period of time although the sharp peak is attained after a longer time than a point source epidemic.
This occurs because of prolonged and repeated exposures or when the source of infection is not eliminated.
Fall in no. of cases is interrupted by'Secondary wave/ Peaks
Examples: Contaminated well in a village nationally distributed brand vaccine or food, a prostitute in a gonorrhoea outbreak, LEGIONNAIRE'S DISEASE outbreak in Philadelphia (1975)
For example, a prostitute may be a common source in a gonorrhoea outbreak but in this case, epidemic curve will rise gradually as she infects her clients over a period of time. But in case of waterborne cholera, the epidemic curve reaches a sharp peak but tails of gradually. These are the two different models of common source continuous epidemic.

B. Propagated Epidemic.

A propagated epidemic occurs due to transmission of the infectious agent either
Person to Person
Through Vectors (insects etc)
Through animal reservoir
The epidemic curve shows gradual rise and tails of over a much longer time as compared to common source repeated exposure epidemic.
Examples: HIV, tuberculosis

Steps for Investigation of Epidemic :

Verification of diagnosis :
Is the first step in investigation of an epidemic'
Confirmation of existence of an epidemic:
Compare with disease frequencies during same period in previous years
Searching for more cases: Search for new cases is carried out every day, till the area is declared free of epidemic; this period is usually taken as 'twice the incubation period of the disease since the occurrence of last case'

Don't Forget to Solve all the previous Year Question asked on Epidemic

weeksvocassithand.blogspot.com

Source: https://medicoapps.org/m-epidemic/