17a-Richardson When Mollusks Attack!

When Mollusks Attack!or

Laboratory/Epidemiology Cooperation During a Typhoid Fever Outbreak in Texas, 2003

Matt Richardson, Epidemiologist

Texas Department of Health, IDEAS Foodborne Team

8th Annual PulseNet Update Meeting

April 28, 2004

Goals of this Presentation• Present information on the value of laboratory

data for epidemiological investigations.• Illustrate how epi data can reduce the sample

burden to the laboratory personnel.• Dispel 2 Myths of Epidemiologists:

1.) Epidemiologist simply take lab data, write it up, and take credit for other people’s work.

2.) Epidemiologists are conference junkies.

• Dispel 1 Myth of Epidemiologists:1.) Epidemiologists simply take lab data, write it up,

and take credit for other people’s work.Well, at least I hope to clarify more of what it meansto “give the data to the epidemiologists” – and providea little levity along the way.

Anatomy of an Investigation:Step 1 – Someone notices something peculiar.

• Examples include: Unusual disease, unusual expression of disease, appearance of a common link between cases.

• In this case, Joan Rogers with the Houston Health and Human Services PulseNet Laboratory noticed that one of her Salmonella gels had:– 2 indistinguishable isolates of S. Typhi– Isolates with submission dates within a week or so of each other.– This was a new pattern which was different from other clusters

normally seen in the database.

Lab data

Anatomy of an Investigation:Step 2 – Epidemiology is Alerted.

• Examples include: Local/Regional/State HD• Joan alerted appropriate epidemiologists (Bill Sorensen

with City of Houston, Syed Ibrahim with Montgomery County).

• Note: Without this notification, the epidemiologists would not have been notified until the final lab report made its way from the lab reporting section to the surveillance database, a delay of up to 14 days.

Lab data Epidemiology

Anatomy of an Investigation:Step 3 – An Investigation is Launched


City of Houston Epi Montgomery County Epi

•Is it unusual to see 2 cases in a week?

•At what rate would we expect to see Typhoid Fever cases?

•How many per year?

•What do we know about the disease?

•How is it transmitted?

•What are the reservoirs?

•What questions should we ask?

Incidence of Typhoid Fever

• Worldwide:– ~ 17 million cases per year– ~ 600,000 deaths per year– Endemic areas: Indian subcontinent and other low income areas

in Asia, Africa, Mexico, Central and South America

• United States:– The U.S. has no endemic Typhoid Fever. Most cases occur in

persons who have recently traveled to an endemic area.

• Texas:– Approximately 2 dozen cases per year– 80% have recent history of international travel– 20% are lost to follow-up but suspected of having had recent

international travel due to PFGE evidence.

Transmission of Typhoid Fever• Only reservoir is humans, either as symptomatic cases or

asymptomatic carriers.• S. Typhi are found in urine- and fecally-contaminated

food and water in many parts of the world.

• Important vehicles:• Untreated water• Fruits and vegetables fertilized with human waste

and eaten raw• Milk and milk products (usually contaminated by

hands of carriers) • Shellfish taken from sewage-contaminated beds

(particularly mollusks)

Clinical Characteristics:• Constipation (more frequently than diarrhea) in adults,

making sample collection problematic• Case-fatality rate 10-20% without prompt antibiotic

therapy• Incubation period 3 days – 5 weeks,

• usually 8-14 days• depends on infecting dose

• Duration of illness increases with increasing severity• 2 - 5% of patients become chronic carriers• Chronic carriers are most often persons infected during

middle age, especially women . . .

A bit of background . . .Salmonella enterica, serovar Typhi

Typhoid Mary

• Real name: Mary Mallon• Sept. 23, 1869 – November 11, 1938 • Irish immigrant who contracted typhoid fever at some

point in her life but only suffered a minor case.• Worked as a cook in in the summer of 1906 for banker

Charles Henry Warren and his family at a rental vacation home in Oyster Bay, NY.

• The cause of various outbreaks at multiple jobs as a cook, Mallon is attributed with infecting 47 people with typhoid fever, 3 of whom died.

• First person found to be a healthy carrier of typhoid fever in the United States.

Anatomy of an Investigation:Step 3 – An Investigation is Launched

• Epidemiologists find the cases, contact them, and administer a Typhoid Fever Investigation Form. We want to know:– How did each individual contract Typhoid Fever?– What, if anything, do these individuals have in common?

• Travel?• Geography?• Onset of illness?• Occupation?• Common restaurants?• Common foods?• Common contacts?



12 miles apart.

Denied international travel.

Dissimilar

Chicken, raw oysters

Same chain, 2 different locations

None found.

3 days apart (8/14/03 vs. 8/16/03)

Hmmm . . .

• PFGE tells us it’s more likely than not that there’s some kind of common source.

• The two cases consumed similar items but in different restaurant locations.

•Common source of food items?

•Common food handler?

• More cases might be out there . . .

• Might be a carrier out there . . .

Anatomy of an Investigation:Step 4 – Investigation is Expanded



Texas Departmentof Health

Are there other cases in the State?

Search State database

Initiate ActiveSurveillance inHouston area

Anatomy of an Investigation:Step 5 – New Data Collected




Are there other cases in the State?

Initiate ActiveSurveillance inHouston area

None found without

international travel.

Lab data –3rd Houston Case

Search State database

Anatomy of an Investigation:Step 6 – Investigation Expanded

Epidemiology



Lab data –3rd Houston Case

Harris County Epi

• Both cases ate the same item (raw oysters), but at different restaurant chains.

• Both cases ate similar items (chicken dishes) at different locations of the same restaurant chain.

Trace food handlers for common work history

Trace food items backfor common source

PulseNet –Cases in other states?

International travel?Texas travel?Raw oysters?

Chicken?Same restaurants?

Anatomy of an OutbreakStep 6, continued – Investigation Expands Further

• 3 additional PFGE-related cases reported over the next several weeks:• 2 Austin area case• 1 San Antonio case

PFGE for all cases of Typhoid Fever in Texas, 2003

Preliminary Epidemiologic Findings

• No recent international travel• No restaurant exposure common to > 2 cases• No other common exposure identified

• Despite multiple interviews with each case

• This had become ugly rather quickly:• Intra-agency: Considerable pressure from above to solve the

outbreak• Political: The oyster industry generates millions of dollars for

Texas and doesn’t like to be unfairly maligned.• Bioterrorism: S. enterica serovar Typhi is on the Select Agent list,

even if it is a “junior varsity” member.

Satan Escapes From Hell

Anatomy of an Investigation:Step 7 – Investigation Deepened

City of Houston

Montgomery County

Texas Departmentof Health –

Other cases in Texas?

TDH Lab

Harris County


Houston Lab

Austin-Travis County

San Antonio

Verifies no otherstates involved

•Further questioning of caseswith in-depth questionnaire

Further Epidemiologic Investigationby all Jurisdictions

(Austin, Harris Co., Houston, Montgomery Co., San Antonio)

• In-depth exposure histories obtained using a 14 page questionnaire:

• Food frequency questions for foods eaten at home• Categories of restaurants and some specific examples provided• Specific questions about raw shellfish consumption

• Cases asked to collect personal calendars, credit card receipts, travel documentation to assist in recall.

All 6 cases identified raw oyster consumption during 5 weeks prior to onset!

The Delicious Oyster, in all its Glory

Case-Patient Characteristics (n=6)

6 Cases: 5 Male, 1 FemaleMedian Age: 35.5 yearsAge Range: 24-54 yearsAverage Incubation Period: 27 days (range 18-40 days)

International travel: 0/6 (0%)Raw oyster consumption: 6/6 (100%)Exposure period: 7/14–8/2/2003Illness onsets: 8/14-9/3/2003Severity of illness: 4/6 hospitalized

2 with critical illness

Anatomy of an Investigation:Step 8 – Traceback of Suspect Product

City of Houston

Montgomery County



TDH Lab

Harris County


Houston Lab


San Antonio



• Raw oyster traceback

Oyster sacks with traceback tags

Oyster Traceback

• Oysters consumed by all 6 cases were traced to:– The same private oyster lease site in Galveston Bay– Harvested by the same company– Using the same boat (#3)– With the same crew of 3 men aboard.– Who harvested all the implicated oysters during a 12-day period

(7/13-7/25/03)– Oysters were consumed from July 14 through August 2, 2003.

– This lease site was closed for harvesting immediately by order of TDH Seafood Safety to prevent further illness.

Boat #3, a.k.a. “SS Typhoid Mary”

Anatomy of an Investigation:Step 9 – Facility Investigation

City of Houston

Montgomery County



TDH Lab

Harris County


Houston Lab


San Antonio




• Investigation of Oyster Plant

Oyster Plant Investigation• Trace forward of oysters:

• No remaining fresh oysters• Some oysters remained, but had been mixed with oysters from

other lease sites not implicated in the outbreak.• Oyster sample tested by TDH Consumer Micro. Lab• No S. Typhi found

• Evaluation of the oyster plant and harvest boat• Collected environmental samples from oyster plant and boat surfaces,

fresh oysters from harvest site, swabs of the dredge tables, boat decks, boat toilet, and washing tables.

• No S. Typhi found

• Evaluation of plant workers:• Interviewed employees• Clinical specimens obtained and tested by TDH Clinical Bacteriology

Lab and Diagnostic Serology Lab• No S. Typhi found, nor were any workers serologically positive.

Employee Investigation

• 18/28 traveled to Mexico Since January 2003

• 1/18 reported a febrile illness, in May 2003

• 1/18 reported remote history of typhoid fever

• 27/28 employees serum and serial stool specimens negative

• 1/28 had titer 1:80– Negative for carrier state– No febrile illness, 2 negative stools– Did not work on Boat #3 or as washer

Anatomy of an Investigation:Step 10 – Case-Control Study

City of Houston

Montgomery County



TDH Lab

Harris County


Houston Lab


San Antonio





• Case-Control study to establishstatistical relevance of findings

2 cases, 10 controls

Austin HoustonSan Antonio

1 case, 5 controls

1 case, 5 controls

2 cases, 10 controls

Case-Control Study Population

Raw Oyster Consumption July 14–August 2, 2003

280

26

Cases Controls

Ate oysters

Did not eat oysters

8

28

6 30

OR undefined, 95% CI 8.1-undefined

36

Standard 2x2 Table for Calculating Odds Ratio:

Case-Control Study Results

• 1:5 age-, sex- and neighborhood-matched study• 2 of 30 (7%) controls had raw oyster consumption• 6 of 6 (100%) cases had raw oyster consumption• Adjusted Odds Ratio 148.2

• 95% CI 7.8 – infinity• P = 0.00001

Anatomy of an Investigation:Step 11 – Feedback

City of Houston

Montgomery County



TDH Lab

Harris County


Houston Lab


San Antonio





• Case-Control study to establishstatistical relevance of findings

• Provide Feedback to the Labs

Conclusions

• First U.S. outbreak of typhoid fever linked to raw oyster consumption since 1954.

• 6 cases of typhoid fever were linked to raw oyster consumption.

• The source of the oyster contamination was not pinpointed:• Could have happened during harvesting• Could have happened at the lease site

• But there have been no new cases after application of the intervention (closing the lease site).

“Good surveillance does not necessarily ensure the making of right decisions, but it reduces the

chances of the wrong ones.”

Alexander D. Langmuir

NEJM 1963;268;:182-191

Implications for Lab/Epi Cooperation• This outbreak probably never would have

been discovered without the vigilance of the PulseNet labs in Texas.

• PFGE of all S. enterica serovar Typhi isolates was critical to this success.

• Epi data gives meaning and context to PFGE results.

• The more cooperation between the labs and their epidemiologists, the more likely outbreaks will be found and solved sooner.

We would like to acknowledgethe hard work of all of the following people:• Montgomery Co. Health Department

S. Ibrahim (epidemiology)

• Houston Health and Human ServicesW. Sorensen (epidemiology)J. Rogers, A. Doggett (Houston HHS Lab)

• Harris Co. Public Health and Environmental ServicesC. Kilborn, D. Martinez (epidemiology)

• San Antonio Metropolitan Health DistrictE. Flores, R. Sanchez (epidemiology)

• Austin-Travis County Health and Human ServicesJ. Schultz, M. DaSilva, E. Sherwood (epidemiology)

• Texas Department of HealthA. Valle-Rivera, A. Toguchi, E. Casey, J. Stringer, M. Kingsley (TDH Lab)L. Gaul, M. Richardson, S. Avashia, H. Lin, R. Jones (epidemiology)K. Wiles (seafood safety)

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17a-Richardson When Mollusks Attack!