Transcript Epidemiology - University of Tennessee

Use of Epidemiology in Field
Settings
and Experiences on the Front
Lines of Public Health:
The Life of an EIS Officer
Jennifer Gordon Wright, DVM, MPH, DACVPM
Centers for Disease Control and Prevention
[email protected]
Public Health
“is what we, as a society, do
collectively to assure the conditions
in which people can be healthy.”
Institute of Medicine, The Future of Public Health, 1988
The Veterinary Oath
• Being admitted to the profession of
veterinary medicine, I solemnly swear
to use my scientific knowledge and
skills for the benefit of society through
the protection of animal health, the
relief of animal suffering, the
conservation of animal resources, the
promotion of public health, and the
advancement of medical knowledge.
Emerging
Zoonoses
• 1415 species of infectious agents
reported to cause disease in humans
– Viruses, prions, bacteria, rickettsia, fungi,
protozoa, helminths
– 868 (61%) are known to be zoonotic
• 175 species considered “emerging”
– 132 (75%) are known to be zoonotic
Taylor et al. Risk factors for disease emergence. 2001, Philosophical
Transactions, The Royal Society, London
The Long and Winding Road…
Bachelor of Science in Microbiology, Auburn University
– Interest in working at CDC, but in what capacity?
• DVM from Auburn University, 1998
– Planned a career in small animal practice or with a drug
company
– Turning point – a lecture in sophomore PH lecture about a
human case of plague
• Went into practice for a few years
– Found the EIS program while searching the web for jobs
• Began MPH work in 2000, worked at CDC
• Entered EIS in July 2002
History of CDC
• 1946 - Communicable Disease Center founded
in Atlanta by Dr Joseph W Mountin
• 400 employees, mostly engineers and
entomologists working on malaria prevention
– Original focus on vectorborne and zoonoses
• Growing awareness that expansion to all
communicable diseases was necessary
CDC today
• One of 13 components of DHHS
• >8000 employees
– Headquarters – Atlanta, Morgantown, Ft. Collins,
Cincinnati, Hyattsville
– State health departments
• International reputation
• Applies research and findings to improve daily lives
• Respond to health emergencies
• Not just infectious diseases
– Chronic diseases, injuries, workplace hazards,
disabilities, environmental health threats
How CDC operates
• Jurisdiction over:
– Cruise ships docking
in US ports
– Importation of
people/animals with
communicable
disease
• Otherwise, need
invitation of the state or
reservation to assist
Veterinarians at CDC
As of December 2005
State Health Departments (14)
Reproductive Health (1)
Bioterrorism (2)
Injury Prevention (1)
AIDS/STD (8)
Bacterial Diseases (10)
Immunizations (2)
Environmental Health (12)
Quarantine (2)
Office of the Director (6)
USDA liaisons (2)
Viral Diseases (13)
Parasitic Diseases (5)
Vectorborne Diseases (4)
Laboratory Animal Issues (7)
NIOSH (4)
What is the EIS Program?
• Epidemic Intelligence Service (aka “Disease
Detectives”)
• Established in 1951
• Mission: To prevent & control communicable
diseases
• A 2 year training program in applied
epidemiology
• Domestic and International Service
– Respond to Requests for Epidemiologic Assistance
EIS
continued
• 55-75 officers, 6-9% are veterinarians
• Applications are due in October for the
following year’s class
• Additional training or experience in public
health encouraged prior to application
• http://www.cdc.gov/eis/about/about.htm
So What is Epidemiology?
• The science of studying patterns of
disease in populations and the factors
that determine such patterns and the
utilization of such knowledge for
diagnosis, control, and prevention
So What is Epidemiology?
• The science of studying patterns of
disease in populations and the factors
that determine such patterns and the
utilization of such knowledge for
diagnosis, control, and prevention
• The study of why some get sick and
some don’t
So What is Epidemiology?
• The science of studying patterns of
disease in populations and the factors
that determine such patterns and the
utilization of such knowledge for
diagnosis, control, and prevention
• The study of why some get sick and
some don’t
• The study of skin… 
Epidemic
• Dorland’s defines as:
– Disease attacking many people at the same
time, widely diffused and rapidly spreading
– Excessive occurrence of disease
Descriptive epidemiology
• Who
– is affected (gender, age, race/ethnicity)
• What
– disease is causing the problem
• Where
– is outbreak occurring
• When
– did the outbreak occur
Analytic epidemiology
• Why
– Did the outbreak occur
• How
– Risk factors for illness
– Examples:
• Eat a certain food item
• Swam in contaminated lake
• Exposure to ticks
Establishing Causality
(continued)
Hill’s Causal Criteria
• Strength of association
– Magnitude of the risk (Odds Ratio, Relative Risk)
• Temporality
– Exposure must precede outcome
• Dose-response
– The greater the dose the greater the risk
• Consistency
– The association between risk factor and outcome is
consistent across studies, samples, populations,
etc.
Establishing Causality
(continued)
Hill’s Causal Criteria
• Biological plausibility
– Association is biologically rational
• Coherence
– Association is consistent with pathogenesis
of disease, similar known associations exist
• Specificity
– one exposure equals one outcome
Outbreak investigation
•
•
•
•
•
•
•
•
Establish a case definition (epi vs. lab)
Find cases
Determine if an epidemic has occurred
Characterize the epidemic in space and time
Investigate risk factors
Formulate/test hypotheses (case-control)
Design control/prevention strategies
Monitor and evaluate for recurrence
Risk factors
• Specific exposures or characteristics
associated with disease, i.e. age,
gender, breed, race, nutritional status,
physiological status, activities,
employment, housing, etc.
Characterizing risk factors
• Relative Risk
• Odds Ratio
• Attributable Risk
The Association between a
Risk Factor and a Disease
Disease
Risk
Factor/exposure
Yes
No
Yes
A
B
No
C
D
A+C B+D
A+B
C+D
Risk Ratio
A
A+B
divided by
C
C+D
Odds Ratio
AD
BC
Come Sail Away:
Cruise Related Illness,
Caribbean, 2002
Vessel Sanitation Program
(VSP)
• 24 hours before arrival in US port ship
physician must report number of passengers
seen for acute gastroenteritis (AGE)
• > 2.0% of passengers/crew with AGE –
special report
• > 3.0% of passengers/crew with AGE –
outbreak investigation
Timeline
• September 28, 2002
– 1980 passengers, 941 crew
• October 2, 2002
– 79 (4.0%) of 1980 passengers with
acute gastroenteritis (AGE)
– No crew reported illness
• October 3, 2002
– CDC team boarded the ship in the Cayman
Islands
Objectives
• Determine the etiologic agent
• Determine the source of the outbreak
• Implement control measures
Methods
Epidemiologic
• Case Finding
-GI logs
-Survey
• Case-control study
-Survey data
• Illness onset
• Symptoms of illness
• Illness-associated
risk factors
Other
 Environmental
inspection
 Stool collection
-Laboratory testing
• Viral
• Bacterial
Survey Case Definition
• Diarrhea (3 or more loose or watery
bowel movements in a 24-hour period)
OR
• Vomiting with 1 of the following:
• Abdominal cramps, nausea, fever
AND
• Onset September 28 - October 4, 2002
Case-Control Definitions
Case
• Illness onset 9/29 or 9/30
• Excluded secondary cases:
– Persons who met the case definition but
cabin mate had onset of illness > 24 hours
prior
Control
• Persons on the cruise who did not report
diarrheal illness, vomiting or accompanying
symptoms between September 28 and
October 4, 2002
Results
Laboratory Results
• 4 of 11 specimens – Norovirus
Norovirus
• ssRNA, Caliciviridae
• Norwalk-like virus
• Incubation
– 24 to 48 hours
• Acute onset
– Vomiting, non-bloody diarrhea
• Duration
– 24 to 60 hours
• Asymptomatic – 30%
• Transmission – easy
Survey Results
• Response Rate
– 1897 (96%) of 1980
• Attack Rate
– 356 (19%) of 1897
• We randomly selected 83 ill persons and 152 controls
from our returned surveys
– 55 cases: onset September 29
– 28 cases: onset September 30
Cases of vomiting or diarrhea among passengers and
crew, cruise ship C, by date of onset (6-hour periods),
Sept 27 to Oct 4, 2002
70
60
crew
50
Number
Date of
embarkation
40
passengers
30
20
10
date and time of illness onset
10/04:12
10/04:00
10/03:12
10/03:00
10/02:12
10/02:00
10/01:12
10/01:00
09/30:12
09/30:00
09/29:12
09/29:00
09/28:12
09/28:00
09/27:12
09/27:00
0
Cases of vomiting or diarrhea among passengers and
crew, cruise ship C, by date of onset (6-hour periods),
Sept 27 to Oct 4, 2002
Case Control Study period
Case Control Study period
70
60
crew
50
Number
Date
Dateof
of
embarkation
embarkation
40
passengers
30
20
10
date and time of illness onset
10/04:12
10/04:00
10/03:12
10/03:00
10/02:12
10/02:00
10/01:12
10/01:00
09/30:12
09/30:00
09/29:12
09/29:00
09/28:12
09/28:00
09/27:12
09/27:00
0
Descriptive Results
• Age
– Cases: median 54 years
– Controls: median 51 years
• Gender
– Cases: males 43%
– Controls: males 42%
Risk Factors
• Significant
– Restaurants
– Food
– Activities
• Not Significant
– Unbottled water consumption
Restaurants
• 4 main restaurants
– 1 and 2 shared a galley
– 3 and 4 shared a galley
• 6 specialty restaurants
– Additional cost to eat in these
Restaurant-Illness associations
Restaurant
Onset 9/29
(n=55)
Lunch 9/28 (Rest 1 & 2)
number of cases
OR (95% CI)
p-value
48 (87%)
2.5 (1.0, 5.9)
0.037
Dinner 9/28 (Rest 3)
number of cases
OR ( 95% CI)
P-value
22 (27%)
2.5 (1.3, 4.8)
0.007
Food, Restaurants 1 and 2
onset of illness Sept 29
Lunch (9/28)
Seafood Salad
number of cases
OR (95% CI)
P-value
Roasted Steamship (beef)
number of cases
OR (95% CI)
P-value
Onset 9/29
(n=48)
24 (50%)
2.5 (1.5, 5.6)
0.001
8 (17%)
5.4 (1.5, 18.7)
0.004
Activities
Onset of illness Sept 30
Onset 9/30
Casino
(9/29)
8:45 Concert
(9/29)
Hot tub
(9/29)
Cases
(n=28)
13 (46%)
Odds
Ratio
3.4
95% CI
P-value
1.4, 7.8
0.004
13 (46%)
3.8
1.6, 9.0
0.001
8 (29%)
2.8
1.1, 7.2
0.030
Limitations
• Number of food items served
– >200 in 2 days
• Time between exposure and survey
– 6 days after suspect foods served
• Passenger discussions
• Asymptomatic infections as high as 30%
– Controls could have been infected
Discussion
• Foodborne
– Galley worker reported illness 9/27
– Distributor prior to bringing on ship
• Norovirus outbreak
• Illness onset on Sept 29th
– due to a food item
• Illness onset on Sept 30th
– Person-to-person spread
• Aggressive control measures by cruise line may have
led to less person-to-person spread than in other
outbreaks
Control Measures
• Before CDC team arrival
– Heightened disinfection: 1000 ppm chlorine
on hard surfaces
– Food serving procedures: gloves, no self
serve buffets
• After CDC team arrival
– Soft fabric disinfection
– Cruise line mandated any ill passenger be
confined to cabin for 24 hours
Recommendations
• Prompt and aggressive control
• Environmental contamination
• Food safety
– Proper handling
– Hand washing
• Strategies to improve employee
reporting of illness
First Outbreak of Monkeypox in the
Western Hemisphere, 2003
Monkeypox
• Orthopoxvirus, related to smallpox
• Restricted to Africa (West Africa, DRC)
• Zoonotic disease
– Wildlife reservoir unknown
– Antibodies to virus found in rodents
– Primates and humans accidental hosts
• Clinically resembles smallpox
–
–
–
–
–
Vesicular rash
Lymphadenopathy
Case fatality < 15%
Limited potential for human-to-human spread
9 day incubation period
Multistate Monkeypox
Outbreak, 2003
Purchase PD
at swap meet
PD bites child
Child ill
Lesions appeared at site of a bite from a sick PD on May 13th.
Family had purchased 2 PDs from a swap meet on May 11th.
6/ 11/03
6/ 10/03
6/9/03
6/8/03
6/7/03
6/6/03
6/5/03
6/4/03
6/3/03
6/2/03
6/1/03
5/ 31/03
5/ 30/03
5/ 29/03
5/ 28/03
5/ 27/03
5/26/03
5/ 25/03
5/ 24/03
5/ 23/03
5/ 22/03
5/ 21/03
5/ 20/03
5/ 19/03
5/ 18/03
5/ 17/03
5/ 16/03
5/ 15/03
5/ 14/03
5/ 13/03
5/ 12/03
5/ 11/03
On May 20, 2003 a 3 year old Wisconsin girl became ill with fever
and presumed cellulitis.
Skin Lesions, Index Case
(3 year old child)
Marshfield Clinic, WI
DAY 11
Mother ill
Dealer ill
Purchase PD
at swap meet
Child ill
PD bites child
6/ 11/03
On May 23rd, the exotic animal dealer that sold the family their
PDs became sick.
6/ 10/03
6/9/03
6/8/03
6/7/03
6/6/03
6/5/03
6/4/03
6/3/03
6/2/03
6/1/03
5/ 31/03
5/ 30/03
5/ 29/03
5/ 28/03
5/ 27/03
5/26/03
5/ 25/03
5/ 24/03
5/ 23/03
5/ 22/03
5/ 21/03
5/ 20/03
5/ 19/03
5/ 18/03
5/ 17/03
5/ 16/03
5/ 15/03
5/ 14/03
5/ 13/03
5/ 12/03
5/ 11/03
On May 26th, the child’s mother became ill.
Wisconsin Animal Dealer,
Primary lesion
Mother ill
Purchase PD
at swap meet
Poxvirus
on EM,
WI DOH
notified
Dealer ill
PD bites child
Child ill
6/ 11/03
6/ 10/03
6/9/03
6/8/03
6/7/03
6/6/03
6/5/03
6/4/03
6/3/03
6/2/03
6/1/03
5/ 31/03
5/ 30/03
5/ 29/03
5/ 28/03
5/ 27/03
5/26/03
5/ 25/03
5/ 24/03
5/ 23/03
5/ 22/03
5/ 21/03
5/ 20/03
5/ 19/03
5/ 18/03
5/ 17/03
5/ 16/03
5/ 15/03
5/ 14/03
5/ 13/03
5/ 12/03
5/ 11/03
The Marshfield Clinic grew virus from mother and PD identified as
a poxvirus by EM.
The WI DOH was notified of illnesses in all parties, initiated
traceback on Prairie Dogs and notified CDC.
Monkeypox
confirmed Executive
Poxvirus at CDC
Order
on EM,
by PCR
FDA/CDC
WI DOH
notified
Mother ill
Purchase PD
at swap meet
Dealer ill
PD bites child
Child ill
6/ 11/03
CDC and FDA issued a joint emergency order prohibiting trade
and movement of PDs and African rodents.
6/ 10/03
6/9/03
6/8/03
6/7/03
6/6/03
6/5/03
6/4/03
6/3/03
6/2/03
6/1/03
5/ 31/03
5/ 30/03
5/ 29/03
5/ 28/03
5/ 27/03
5/26/03
5/ 25/03
5/ 24/03
5/ 23/03
5/ 22/03
5/ 21/03
5/ 20/03
5/ 19/03
5/ 18/03
5/ 17/03
5/ 16/03
5/ 15/03
5/ 14/03
5/ 13/03
5/ 12/03
5/ 11/03
CDC confirmed monkeypox in samples from mother and PD.
2003 Monkeypox
Outbreak Characteristics
• 47 human cases in 5 states
• All cases reported contact with sick prairie dogs
• No clear person-to-person spread
• High hospitalization rate for quarantine/infection control
issues
• Over 25% of cases occurred in veterinary staff
• First outbreak of monkeypox in humans outside Africa
Animal Traceback
• All sick prairie dogs were traced to an IL dealer
• IL dealer had African rodents (Gambian rats and
dormice) on the premises
• Traced movements of all prairie dogs and African
rodents
• Tracing capabilities limited
– Cash sales, often no record
– Trade at swap meets- widespread distribution
– Dealer recall limited
– Exposure without ownership (contact in store…)
Movement of Imported African Rodents to Animal
Distributors and Distribution of Prairie Dogs from
Point of Infection
MMWR July 2003
NJ
Rodent Shipment from Accra, Ghana
4/9/03
4/9/03
?
TX 2
GR
RS, BTP
SS
TX 1**
50 Gambian rats (GR)
53 rope squirrels (RS)
2 brush-tailed porcupines (BTP)
4/11/03
47 sun squirrels (SS)
100 striped mice (SM)
~510 dormice (DM)
WI
Human cases:
17 confirmed
22 probable/
suspect
TX 3
42 PDs
traced
RS, SM
DM
14 PDs
traced
IA†
4/17/03
IL 1§
4/21/03
TX 5
DM
DM
200 prairie dogs (PDs)
in existing inventory
1 PDs
traced
TX 6
11 PDs
traced
TX 9
4/28/03
TX 7
TX 8
MI
DM
DM
No human
cases
4/29/03
5/12/03
TX 10
DM
June 2003 lab
confirmation:
diseased animals
derived from shipment
SC
DM
No human
cases
IL 2
DM
6/1/03
Japan
DM
MN
DM
6/1/03
WI
DM
Human cases:
7 confirmed
9 probable/
suspect
MO
Human cases:
2 confirmed
1 PD
traced
4/26/03
SS, SM
DM
IN
24 PDs
traced
GR, DM
GR, DM
TX 4
IL‡
Human cases:
8 confirmed
4 probable/
suspect
KS
Human cases:
1 confirmed
Gambian Giant (Pouched) Rat
Striped Mouse
Rope Squirrel
Sun Squirrel
Evidence of monkepox infection in laboratory testing
Dormouse
Reasons for the 2003
Monkeypox Outbreak
• Unrestricted importation of animals from Africa
– Wild caught animals with unknown history
• Exotic pet trade allows rapid movement of animals
– Not regulated by federal statues
– No requirements to maintain records
• Human medicine is not familiar with monkeypox
– Did not recognize lesions as smallpox-like
– Delayed reporting of “unusual illness” to state
authorities
Thyrotoxicosis
• South Dakota, June 1985
• Eight persons aged 29-76 years (5
men)
• Symptoms: anxiety, palpitations,
dyspnea, weight loss, tachycardia
• Signs: elevated T4, low RAIU
• Onset: May - June 1985
Background
• Cases clustered in two SD towns (near
MN)
• Interviewed eight patients
• No common exposures
• Drew blood from patients and family
• Tests run
Preliminary Investigation
• Case-finding
– 33 additional patients who in the past year
had
• High T4
• Low RAIU
• Cases clustered around Luverne, MN
• Results from other 8 patients' families:
– 75% of asymptomatic family members had
elevated T4s
Further Findings
•
•
•
•
•
Total: 121 cases
Age range: 0-76 years
Sex: 62 male, 59 female
Onset: April 1984-August 1985
Location: Clustered around MN-SD
border
Case-Control Study
• Cases: first patient in household
• Controls: same phone exchange
• Questions:
–
–
–
–
–
–
History of viral illness
Ingestion of Iodine-containing food
Medications
Toxic exposures
Food additives/Health food products
Contacts with others who were ill
Additional Findings
• New patient from outside the area
–
–
Shopped at a grocery store in area
All foods national brands except:
•
•
Fresh chicken eggs
Beef trimmings from plant A in Luverne, MN
• One family: all members were cases except
one boy (vegetarian)
• Case-control study implicated beef trimmings
from Plant A
Summary
• "Before April 1983 thyroid glands were
selectively removed and sold for use in the
manufacture of thyroid extract. After that
time, 'gullet trimming' was employed to
harvest muscle from the bovine
larynx...motion allowed portions of both lobes
of the thyroid gland to be inadvertently
included in the muscle trimming...“
• Thyroid was being ground up with muscle and
ingested as part of ground beef
Salmonellosis
• January 1981 call to CDC:
– 36 cases Salmonella munchen in Jefferson
Co., OH
since mid-December 1980
• 26 cases with same serotype in Lansing,
MI
Descriptive Epidemiology
– Age range: 1 month - 76 years
– 28% of patients aged 20-29 years
– Located in 3 disparate neighborhoods in
Jefferson County, OH
Investigation
• No common exposures among cases
except ham
• Brands/Types of hams different
• All ham cultures negative
• Other activities to consider?
• Ongoing source of infection?
• Weekly stool cultures all positive
• One turned negative -- pregnant woman
Pregnant Woman - Key
• Interviewed pregnant woman for
activities (in which she no longer
participated)
Pregnant Woman - Key
• Interviewed pregnant woman for
activities (in which she no longer
participated)
– Smoking
– Drinking alcohol
– Smoking marijuana
“Smoking” Gun…
• Upon further questioning:
– At least one member of each casehousehold smoked marijuana
• Marijuana from all households in town
positive for S. munchen
• Biologic plausibility
Infection control survey
Survey of Veterinary Hospital
Infection Control Practices
• AVMA/CDC collaborative effort
• Survey
–
–
–
–
Knowledge
Attitudes
Practices regarding infection control practices
Use of PPE
• WHY?
– To determine current practices
– To determine what additional resources are needed
Methodology
• AVMA 2004 Membership list (n=48,548)
– Employer codes (n=45,185)
– Species Codes
• Small Animal, Mixed Animal, Equine, Large Animal
• Randomly selected veterinarians from
each category to receive a survey
All *
Small
Mixed
Equine
Large
Female
48%
52%
27%
21%
19%
< 10 years in
practice
26%
27%
24%
24%
24%
Owner
58%
54%
78%
66%
72%
≥ 40 hours
per week
66%
61%
86%
86%
84%
5%
6%
0.5%
11%
10%
4%
22%
2%
24%
3%
13%
47%
20%
67%
11%
Teaching
Mobile Only
Policy (yes)
Preliminary results
*weighted population average
Infection control practices
All *
Always wash
53%
hands before eat
May eat in animal
86%
areas
May recap
93%
needles
May re-use
needles
Preliminary results
32%
Small Mixed Equin Larg
e
e
55%
47%
31%
28%
86%
91%
82%
79%
92%
95%
98%
97%
28%
52%
15%
41%
*weighted population average
Engage in protective behavior
when handling…
All*
Small
Mixed
Equine
Large
Healthy animal
57%
58%
56%
16%
76%
Animal wvomiting/diarrhea
25%
24%
40%
52%
54%
20%
16%
37%
18%
62%
44%
27%
44%
26%
47%
34%
16%
14%
69%
54%
4%
5%
1%
1%
0%
Animal wneurologic signs
Feces
Urine
Products of
parturition
Preliminary results
*weighted population average
When looking at veterinarians by
years in practice*
< 10 year
≥10 years
Always wash hands
53%
53%
May eat in treatment
area
Recap needles
Hours per week worked
Owner of clinic
Bitten in last year
Needlestick in last year
Cut by instrument
91%
85%
96%
66%
21%
92%
66%
71%
50%
71%
53%
60%
28%
23%
Preliminary results
*weighted population average
Conclusions
• Zoonoses are of great importance in human health
• Veterinarians are often front line of defense, but do not
protect selves adequately
• Need for written guidance for veterinary profession
• Self-reported behavior not always accurate
• MPH student thesis analysis of small animal practitioners only
demonstrated that males, those in the Midwest and those
working in clinics without written infection control policies
were more likely to have “poor” infection control practices
Compendium Committee
• Representatives from NASPHV, CDC,
academia, AAHA, state and local health
departments
• Tasked to develop written “Universal
Precautions” for veterinarians
• Data from the survey will point to where
gaps exist
Acknowledgements
•
•
•
•
•
•
•
Jennifer McQuiston, CDC
Sherry Jung, Rollins School of Public Health
Nina Marano, CDC
Doug Hamilton, CDC
Marc-Alain Widdowson, CDC
American Veterinary Medical Association
Dr. John New and Katie Portacci, UT
[email protected]