Lecture 10 - Gastroenteritis Epidemiology Flashcards
In general, which pathogens cause vomiting, and which don’t?
Emetic:
- B. cereus
- S. aureus
- rotavirus
- norovirus
Non-emetic:
- extracellular
- invasive
- C. perfringens
Differentiate between food-borne illness and gastrointestinal disease
Some food borne pathogens cause disease that is not gastroenteritis:
- Creuzfeld Jacob
- Hepatitis A
Some gastrointestinal disease is not food borne:
- Person to person
- Petting zoos
- Water borne
Which bacteria can cause dysentery in some cases?
E. coli
Shigella spp.
What are the most common agents of gastroenteritis?
Campylobacter
C. perfringens (to a lesser degree)
What are the most common agents of gastroenteritis in Australia?
Campylobacter
Salmonella
Giardia
C. perfringens (to a lesser degree)
Describe the stages of the pyramid
7 steps
- exposure
- person falls ill
- person seeks care
- specimen obtained
- test performed
- confirmation of infection
- reported to health department
What percent of cases of gastro are reported to the health department?
1%
How many cases of gastro can an Australian expect to have per year?
0.92 –> one case a year
What is the impact of gastroenteritis on Australia?
Many lost days of work
Many trips to the doctor
Financial burden on Government, Businesses, Healthcare
Deaths
What percent of gastroenteritis cases are food-borne?
Around 32%
How many hospitalisation are there per year due to gastro?
What related illnesses also lead to hospitalisations?
Around 40,000
Reactive arthritis, septicaemia
How many deaths per year in Australia due to Gastroenteritis?
What are these usually due to?
200
Haemolytic Uraemic syndrome, infection of the elderly
Explain what happened in London 1848
Many people were dying due to dehydration
No understanding of micro-organisms
Deaths concentrated around a water pump in Broad street
How did John Snow figure out the source of the disease?
Mapped out the deaths –> concentrated around a water pump in Broad street
One family had a case of Cholera – this was the index case. The infected faeces in the cess pit under the house.
Cess pit leaked into the water pipe
Everyone in the area came to get their water from the Broad street pump
When the handle was broken off –> no more cases
What is the index case?
The first case of the disease
What is the definition of epidemiology?
Study of occurence, spread and control of disease
Compare the terms epidemic, pandemic and endemic
Endemic: when a disease is present at low levels, at all times, within a population
Epidemic: rapid increase in number of cases in a country
Pandemic: rapid increases in number of cases across the world
What are some situations in which a point source accounts for infection?
Wedding
BBQ
Group of diverse people come together and share a meal
Rapid number of cases, then it dies out
What are the ways we can describe the time of the outbreak?
- Point source
* Continuing source
What are the features of a continuing source?
Give an example
Relatively slow to peak and decline.
The source of infection is present over a long period of time
Eg. Hep A from contaminated oyesters
What type of graph is an epidemic curve?
Histogram plotting the number of cases occurring on a particular day / week
In a case of Person to person spread, what does the epidemic curve look like?
Increase in number of cases with each generation
How can ‘person’ be described in an outbreak?
The vulnerable demographics
How can ‘place’ be described in an outbreak?
- Map with dots representing the cases
* rates per year in a population
How may ‘Pathogen’ be described in an outbreak?
PFGE: pulse field gel electrophoresis
Why are Case-Control studies used?
The determine the source
Describe the case of gastroenteritis in Ohio teenagers
Salmonella muenchen isolated from affected individuals
41% of affected households contained young adults
Questioning regarding drug use –> Marajuana source
Describe the case of the Chinese Restaurant cases of gastro
- Many people who all ate at a particular restaurant came down with gastro
- Investigators asked everyone what they ate, and managed to track it back to deep fried ice cream
- Same Salmonella phage type isolated from faces of infected people and ice cream batter
Which organisations deal with food-Bourne illness?
State Health Departments
OzFoodNet
WHO
HACCP
What are some challenges in control of Gastro and food-Bourne illnesses
- Modern eating habits
- Globalisation
- Antibiotic use in animals
- Complexity of food handling
Which demographic worldwide is most affected by diarrhoeal disease
99% of deaths due to diarrhoeal disease are in non-industrialised countries
How many deaths per year due to diarrhoea?
1.8 million
What is the aim of analytic epidemiology?
To find the source of the outbreak
Which pathogen is the least common causal agents of gastro in Australia?
Vibrio family
What are the Principles of Outbreak investigation?
- Describe the outbreak
- Develop and test a hypothesis
- Intervene to control outbreak
- Prevent future outbreak
What general things do we need to describe about the outbreak?
- Place
- Time
- Person
- Pathogen
Name two cases of analytic epidemiology
- Chinese restaurant outbreak
* Ohio outbreak
