Download Gastroenteritis Strikes Again

Piqua 2007
Disease Detectives I
Name:_______________
Name:_______________
Team Number: ________
School:______________
Gastroenteritis Strikes Again!
Background: An outbreak of gastroenteritis occurred the evening of April 28. A
total of 89 people went to the emergency room of 3 local hospitals. No more cases
were reported afterwards. The patients complained of headache, fever, nausea,
vomiting and diarrhea.
1. Could this also be called an epidemic? Discuss the pros and cons.
For some epidemic and outbreak are used interchangeably, but outbreak is a
less sensational term. For others epidemic would be reserved for a more
widespread occurrence.
It is clear that 89 cases constitute more cases in a time and place than would
normally be expected.
2. Finish the calculations:
Gastroenteritis Outbreak Findings by Person, Case
Distribution
by Age and Gender
Females
Age Group (y)
%
2
0–5
No.
6–10
2
11-20
21 and older
11.3
Total by gender
100
1
% Females
Males
No.
Total by Age
% Males
No.
50
1
50
38
50.7
37
49.3
75
84.3
1
50
1
50.0
2
2.2
9
90
1
10.0
10
49
55.1
40
2
44.9
2.2
89
3. What name is given to the following curve? EPI(demic) curve
What can you deduce from the curve? Single source outbreak/6 hour onset
Suggests intoxication or food poisoning.
4. Based on the initial findings, what can you tell about the place where the outbreak
occurred? Place where women and young children come together such as an
elementary school
5. What broad categories of agents cause gastroenteritis?
Bacteria, Viruses, Parasites, Toxins
6. Which is the most likely cause? Why?
Bacteria—food poisioning based on incubation period and location.
Turn this part in to receive the rest of the test!
Piqua 2007
Disease Detectives II
Name:_______________
Name:_______________
Team Number: ________
School:______________
1. Complete the following calculations:
2.Where did the outbreak occur? Is this consistent with the previous demographic data?
School Cafeteria. Adult women were teachers.
3.Calculate the AR and RR for people at the implicated location:
4. Which food items were the most likely sources of the outbreak?
Salad and Fruit Cocktail had the highest RR.
5. Two food items had RR’s substantially lower than 1.00. Explain why these foods seem
to have “protected” people from getting gastroenteritis.
Perhaps the menu choices were baked potato or salad.and then Fruit Cocktail or
Ice Cream.
No one involved in food preparation developed symptoms. Manuel prepared the beef
burritos and potatoes. John prepared the salad and the fruit. Sally prepared all dishes
except for the ice cream. Jane prepared the cheeseburgers and served the ice cream. The
ice cream was a commercial brand and bought at a nearby supermarket. Leftovers from
the meal were taken to the laboratory. In addition stool samples were taken from the
kitchen personnel . The laboratory confirmed that Salmonella was found in some of the
food samples and in the stool sample of one of the workers. It was the same species found
in the stool samples of the patients.
6. Identify the worker. Explain how he would have contaminated the food without
becoming ill himself.
John is a carrier. Perhaps he didn’t wash his hands prior to food prep.
7. What should he do before returning to work? Provide evidence that he has improved
his hygienic practices and seek medical treatment for the salmonella organisms that
are most likely in his liver.
8. This case is similar to that the famous Mary Mallon. Explain who Mary Mallon was.
Mary Mallon (September 23, 1869 – November 11, 1938), also known as
Typhoid Mary, was the first person in the United States to be identified as a
healthy carrier of typhoid fever. Over the course of her career as a cook,
she infected 47 people, three of whom died. Her fame is in part due to her
vehement denial of her own role in causing the disease, together with her
refusal to cease working as a cook. She was forcibly quarantined twice by
public health authorities, and died in quarantine.
Part III. MMWR QuickStats
Look at the graph on the following page then answer the following questions:
1. What kind of study is this?
Survey(Cross Sectional Study)
2. What are some of the advantages of this type of study?
Easy to get info
Quick
3. What are some of the disadvantages of this type of study?
Vulnerable to Confounders
Conditons not verified clincially
4. Explain the 95% confidence level in terms of the Hispanic Less than High School
data.
95% likelihood that the % at increased risk is between 10 and 15%.
4. The data show educational attainment was a factor among non-Hispanic black
persons. Suggest a possible reason for this.
Cultural differences.
Part IV. Emerging Infectious Diseases
According to the Jan 2007 issue of Emerging Infectious Diseasses, 75% of emerging
infectious diseases since the end of the 20th century are zoonotic.
1. Give 2 examples of such diseases.
Many examples are acceptable.(Influenza, ebola, monkey pox ….)
2. What are some of the leading causes of their emergence at this point in history?
The leading causes of their emergence are human behavior and modifications to
natural habitats (expansion of human populations and their encroachment on
wildlife habitat), changes in agricultural practices, and globalization of trade.
However, other factors include wildlife trade and translocation, live animal and
bushmeat markets, consumption of exotic foods, development of ecotourism, access
to petting zoos, and ownership of exotic pets.
3. What can be done to reduce the risk for emerging zoonoses?
To reduce risk for emerging zoonoses, the public should be educated about the
risks associated with wildlife, bushmeat, and exotic pet trades; and proper
surveillance systems should be implemented.
Part V. Influenza Pandemics
The 1918 “Spanish flu” H1N1 was the most devastating flu pandemic in recent history,
killing more than 500,000 people in the United States, and 20 million to 50 million
people worldwide—more than the world wars of the 20th century.
1. What is a pandemic? Is a worldwide epidemic.
2. How do they get started? A flu pandemic occurs when a new influenza
virus emerges for which people have little or no immunity, and for
which there is no vaccine. The disease spreads easily person-toperson, causes serious illness, and can sweep across the country and
around the world in very short time.
3. Which populations are generally the most vulnerable? Why?
Young—immune systems not fully developed
Old—immune systems compromised
4. The 1918 pandenic was quite unusual in that the attack rate and mortality rate
was highest among adults 20 to 50 years old.. Suggest a possible explanation.
Any reasonable hypothesis.
5. To what to the H and N refer to in the H1N1 designation?
Avian (bird) flu is caused by influenza A viruses that occur naturally
among birds. There are different subtypes of these viruses because of
changes in certain proteins (hemagglutinin [HA] and neuraminidase [NA])
on the surface of the influenza A virus and the way the proteins combine .
Part VI. Some Basics
List the 10 steps in order in the investigation of an outbreak:
1. Prepare for Field Work
2.Establish the existence of an oubreak.
3.Verify the diagnoses.
4.Define and identify the cases.
5.Describe and orient the data in terms of time.person,place.
6.Develop hypotheses.
7.Evaluate hypotheses.
8. Refine hypoitheses and carry out furether studies.
9. Implement control and preventative measures.
10. Communicate Findings
Part V. Defintions:
1. Virulent—refers to a pathogen that is rapid, severe and malignant.
2. Morbidity—can refer to the prevalence or incidence of a condition(illness)
3. Reservoir—place where an infectious agent can survive but mayu or may not
multiply.
4. Confounder—an unaccounted for variable
5. sensitsivity-- True Positives/(True Positives + False Negatives)
6. 6. specificity--True Negatives/(False Positive + True Negative)
7. Prevalence—the number of cases of a condition that exist in a population at a
given time.
8. Endemic --The constant presence of a disease or infectious agent within a
given geographic area or population group; may also refer to the usual
prevalence of a given disease within such area or group.
9. Cluster—a group of cases close in time or place which may or may not be
related.
10. Biological gradient—relationship between the change in exposure to increase
of decrease of a specific outcome.
Part VI. History
1. John Graunt_a professional haberdasher and serious amateur scientist, published
Natural and Political Observations ... upon the Bills of Mortality in 1662. In it, he
used analysis of the mortality rolls in London before the Great Plague to present
one of the first life tables and report time trends for many diseases, new and old.
He provided statistical evidence for many theories on disease, and also refuted
many widespread ideas on them.
2. Dr. John Snow is famous for the suppression of an 1854 outbreak of cholera in
London's Soho district. He identified the cause of the outbreak as a public water
pump on Broad Street and had the handle removed, thus ending the outbreak.
3. P. A. Schleisner Danish physician, who in 1849 related his work on the
prevention of the epidemic of tetanus neonatorum on the Vestmanna Islands in
Iceland.
4. Ignaz Semmelweis Hungarian physician, who in 1847 brought down infant
mortality at a Vienna hospital by instituting a disinfection procedure.
5. Richard Doll and Austin Bradford Hill British doctors published a report
which lent very strong statistical support to the suspicion that tobacco smoking
was linked to lung
cancer
6. Dr. Jonas Salk developed the first successful polio vaccine in 1950’s
7. Julie Louise Gerberding current head of the CDC.