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YEAR 3 - SEMESTER 1 > CASE 7 - Outbreak Investigation > Flashcards

CASE 7 - Outbreak Investigation Flashcards

1
Q

Hilda Ryan, a 76 year old woman who lives in an aged care complex, phones her GP at 10:00 am to request a home visit because of cramping abdominal pain, nausea, vomiting and diarrhoea since yesterday afternoon.

List 3 questions that you would like to ask her if you suspect a FOODBORNE illness. Explain why these are relevant.

A

“If you recently had a meal with other people, did they also experience these symptoms?” - If yes, increases the likelihood of a foodborne illness.

“Did you notice any blood or mucous in your stool?” - Clue about causative pathogen. Small bowel pathogens tend to cause watery diarrhoea whereas large bowel pathogens cause inflammatory diarrhoea.

“What is your occupation?” - animal contact is a risk factor.

“Any recent travel?”

“What is the nature of your abdominal pain?”

“What did you eat yesterday?” - may give clues about the type of organism

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2
Q

Hilda Ryan, a 76 year old woman who lives in an aged care complex, phones her GP at 10:00 am to request a home visit because of cramping abdominal pain, nausea, vomiting and diarrhoea since yesterday afternoon.

List 3 questions that you would like to ask her if you suspect CHOLECYSTITIS. Explain why these are relevant.

A

“Where is your abdominal pain located?” - usually RUQ if cholecystitis. Can also radiate to the upper back and right shoulder.

“Have you been feeling feverish?”

“Did you eat a fatty meal?” - Hx of fatty food ingestion 1 hour prior to the onset of pain

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3
Q

Hilda Ryan, a 76 year old woman who lives in an aged care complex, phones her GP at 10:00 am to request a home visit because of cramping abdominal pain, nausea, vomiting and diarrhoea since yesterday afternoon.

List 3 questions that you would like to ask her if you suspect GASTROPARESIS. Explain why these are relevant.

A

“Do you feel full very easily?” - early satiety is a sign of gastroparesis

“Have you been experiencing any bloating?”

“Have you been diagnosed with diabetes?” - most frequently recognized systemic disease associated with gastroparesis (note it is often idiopathic)

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4
Q

Hilda Ryan, a 76 year old woman who lives in an aged care complex, phones her GP at 10:00 am to request a home visit because of cramping abdominal pain, nausea, vomiting and diarrhoea since yesterday afternoon.

List 3 questions that you would like to ask her if you suspect GASTRIC OUTLET OBSTRUCTION (GOO). Explain why these are relevant.

A

“Do you feel full very easily?”

“Where is your pain?” - GOO usually results in epigastric

“Have you lost any weight unintentionally?” - malignancy-associated

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5
Q

What types of organisms cause illness within hours of exposure? Why?

A

Staphylococcus aureus, Bacillus cereus, Clostridium perfringens

Ingestion of preformed toxins causes illness within a few hours

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6
Q

What are the most common causative agents of foodborne illness in Australia?

A

Norovirus

Pathogenic E. Coli

Campylobacter spp.

Non-typhoidal salmonella spp.

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7
Q

What types of organisms cause illness 24 hours (or more) after exposure? Why?

A

Salmonella

Campylobacter

Shigella

They are ingested and SUBSEQUENTLY produce pathogens. They also directly invade the intestinal epithelial wall.

UPTODATE: Table 1. Good summaryhttps://www-uptodate-com.proxy.library.adelaide.edu.au/contents/causes-of-acute-infectious-diarrhea-and-other-foodborne-illnesses-in-resource-rich-settings?sectionName=CLINICAL%20CLUES%20TO%20THE%20MICROBIAL%20CAUSE&search=vomiting%20nausea&topicRef=2537&anchor=H1823851406&source=see_link#H2200733743

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8
Q

TRUE OR FALSE? Majority of the causes of foodborne illnesses are of unknown cause.

A

TRUE

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9
Q

Who is most at risk of developing complications from food poisoining?

A

Young children & the elderly

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10
Q

State the following information for NOROVIRUS:

  • Route of transmission
  • Incubation period
  • Classic/common food sources
  • Other epidemiologic causes
  • Type of diarrhoea
A
  • Route of transmission: faecal-oral
  • Incubation period: 24 - 48 hours
  • Classic/common food sources: shellfish, prepared foods, vegetables, fruit
  • Other epidemiologic causes: restaurants, healthcare facilities, schools and childcare centres, military, cruise ships
  • Type of diarrhoea: watery
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11
Q

State the following information for Campylobacter spp:

  • Route of transmission
  • Incubation period
  • Classic/common food sources
  • Other epidemiologic causes
  • Type of diarrhoea
A
  • Route of transmission: faecal-oral, poultry
  • Incubation period: 1-3 days
  • Classic/common food sources: poultry, meat, unpasteurized milk
  • Other epidemiologic causes: travel to resource-limited settings, animal contact
  • Type of diarrhoea: inflammatory
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12
Q

State the following information for ENTEROTOXIGENIC E. COLI (ETEC):

  • Route of transmission
  • Incubation period
  • Classic/common food sources
  • Other epidemiologic causes
  • Type of diarrhoea
A
  • Route of transmission: faecal-oral, recent travel
  • Incubation period: 9 hours - 8 days
  • Classic/common food sources: faecally-contaminated food or water
  • Other epidemiologic causes: travel to resource-limited countries
  • Type of diarrhoea: watery
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13
Q

State the following information for SHIGELLA:

  • Route of transmission
  • Incubation period
  • Classic/common food sources
  • Other epidemiologic causes
  • Type of diarrhoea
A
  • Route of transmission: faecal-oral
  • Incubation period: 1-3 days
  • Classic/common food sources: raw vegetables
  • Other epidemiologic causes: daycare centres, resource-limited settings, MSM
  • Type of diarrhoea: inflammatory
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14
Q

Name 3 organisms that produce watery diarrhoea

A
  • Giardia
  • Norovirus
  • Rotavirus
  • Clostridioides difficile
  • Staphylococcus aureus
  • ETEC
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15
Q

Name 3 organisms that produce inflammatory (bloody, mucoid) diarrhoea

A
  • Nontyphoidal salmonella
  • Campylobacter spp.
  • Shigella
  • EHEC
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16
Q

Mrs Ryan has been suffering from watery diarrhoea after consuming cold chicken and coleslaw. Name a likely causative pathogen.

A

Norovirus (watery diarrhoea, can be caused by prepared foods & vegetables)

Staphylococcus aures (watery diarrhoea, inadequately refrigerated food)

ETEC (watery diarrhoea, undercooked meat)

17
Q

What is the most common cause of traveller’s diarrhoea?

A

ETEC

18
Q

What type of diarrhoea is associated with bacterial causes?

A

Can be bloody or watery

19
Q

What should be the focus of physical exam on a patient with acute diarrhoea?

A
  • Volume depletion (MM, postural hypotension, skin turgor, altered sensorium)
  • Identifying complications
20
Q

Name 3 host factors that increase the risk of complications due to acute diarrhoea

A
  • Age >70

- Comorbidities (e.g. cardiac conditions, immunocompromised)

21
Q

When is microbiological stool testing indicated?

A

SEVERE ILLNESS: >6 unformed stools in 24 hours, signs of hypovolemia, severe abdo pain, hospitalisation

AGE >70

COMORBIDITIES (e.g. Cardiac disease)

IMMUNOCOMPROMISED

SYMPTOMS >1 WEEK

PUBLIC HEALTH CONCERNS (e.g. hospitality & health workers)

22
Q

What is an outbreak?

A

Something that is unexpected

Any unusual or unexpected increase in the number of cases of a particular disease than would normally be expected in a given area, or among a specific group of people, over a particular period of time

23
Q

How is gastroenteritis in residential areas defined?

A

Two or more cases who have vomiting or diarrhoea over a 24-hour period

24
Q

Outline the difference in pathophysiology between watery and inflammatory diarrhoea.

A

WATERY: microorganisms produce toxins that attack secretory mechanisms in the small intestine –> copious watery diarrhoea

INFLAMMATORY: cytotoxin production –> mucosal destruction –> bloody stools with inflammatory cells (and resultant decreased absorptive ability)

25
Q

What is the principal treatment of acute diarrhoea?

A

Rehydration: mostly oral.

IV if severe disease.

26
Q

In which patient groups are empirical antibiotics indicated or recommended?

A
  • Immunocompromised
  • Severe disease

Obtain faecal samples before starting therapy

27
Q

Epidemiologic, traceback, and food and environmental data can be used to investigate an outbreak.

Describe what each of these 3 methods involves.

A
  1. EPIDEMIOLOGIC: patterns in geographic distribution of illness, when people got sick, similar past outbreaks, foods or other exposures occurring in sick people more often than expected, clusters of unrelated people who ate at the same restaurant or attended the same event
  2. TRACEBACK DATA: identifying a common point of contamination (collecting records from places that sick people frequented), safety risks in farms, restaurants, shopping centres, etc.
  3. FOOD & ENVIRONMENTAL TESTING DATA: germ found in food item from the sick person’s home or at the food manufacturing environment
28
Q

What is the route of transmission of Cryptosporidium protozoa?

A

Faecal-oral

e.g. person-person, animal contact, contaminated food or water

29
Q

__________ ______ are of
significant concern because they represent
a potential source of cryptosporodium outbreak that can affect many people

A

SWIMMING POOLS

30
Q

Who is at greater risk of legionella infection?

A

People who are middle aged and older (with weakened immune systems)

Men are more frequently affected

RFs: smoking, >50 years, heart or lung disease, diabetes, kidney failure

31
Q

Compare cohort vs. case-control studies

A

COHORT: prospective, stronger evidence.
A group of people who share a defining characteristic are followed and exposures are recorded over time. The impact of this variable/exposure can be explored.

CASE-CONTROL: retrospective, weaker evidence.
People who have developed a disease are identified. Their past exposures to suspected etiological factors is compared to those who have NOT developed the disease.

https://www.youtube.com/watch?v=RX0qVI1hw-o

32
Q

Steps involved in an outbreak investigation

A

.

33
Q

How to prevent future outbreaks

A

.

34
Q

What you want to find out when there is a suspected outbreak

A

.

35
Q

Define sensitivity and specificity

A

SENSITIVITY = the ability of a test to correctly identify patients with a disease.

SPECIFICITY = the ability of a test to correctly identify people without the disease.

36
Q

Compare sensitivity and specificity

A

Sensitivity allows you to correctly identify whether someone has a disease (true positives). It RULES OUT the disease if you come back negative.

Specificity is a measure of how well a test can identify TRUE NEGATIVES. It RULES IN the disease if you come back positive.

37
Q

Define positive and negative predictive value.

A

Positive predictive value is the probability that subjects with a positive screening test truly have the disease.

Negative predictive value is the probability that subjects with a negative screening test truly don’t have the disease.

38
Q

Define RELATIVE RISK/RISK RATIO and what it means if this number is above or below 1.0

A

RELATIVE RISK: calculated by looking at 2 separate groups (one ‘exposure’ and one ‘control’).

Risk of disease in the exposed group is divided by risk of disease in the control group. A risk ratio of 1.0 indicates identical risk in both groups. A risk ratio greater than 1.0 indicates that those with the exposure are at increased risk. A risk ratio less than 1.0 indicates decreased risk for the exposed group, indicating that perhaps exposure actually protects against disease occurrence.

39
Q

Explain what an ODDS RATIO is

A

Odds ratio quantifies the strength of an association between 2 events (i.e. the association between a risk factor/exposure, A, and a disease, B)

Tells you how the presence or absence of property A has an effect on the presence or absence of property B.

YEAR 3 - SEMESTER 1 (15 decks)

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