Prioritizing investigations of reported cases of selected enteric infections - PowerPoint Presentation

Slide1

Prioritizing investigations of reported cases of selected enteric infections

Richard S. Hopkins, MD, MSPH

Leah Eisenstein, MPH

CSTE annual meeting, Omaha, NE,

June, 2012Slide2

Background

Florida consistently has the highest number, and one of the highest rates, of salmonellosis cases reported among the states

In 2010, there were:

1211 cases of campylobacteriosis

408 cases of cryptosporidiosis

2,139 cases of giardiasis

6,281 cases of salmonellosis

1,212 cases of shigellosis

Peak numbers in last ten years:

Campylobacteriosis 1211, cryptosporidiosis 738, giardiasis 2,139, salmonellosis 6,741, shigellosis 2,845

We serotype fewer than 10% of Salmonella isolates and about 20% of them get a PFGE pattern

This analysis is not about typhoid fever or shigatoxin-producing E. coliSlide3

Background

Our standard approach has been that every reported case of each of these infections should be interviewed

Conversations with county health department (CHD) epidemiology staff indicated some lack of clarity as to the purpose of interviews

Epi staff got considerable satisfaction from educating people with cases about how they might have gotten infected and how they could prevent future illnesses in themselves.

CHD staff were spending a lot of time on follow-up testing of cases in sensitive situations to clear them to return Slide4

Reality bites

Florida CHDs are getting squeezed financially

By their county commissioners

By the state health department/legislature

By Medicaid

CHD directors are gradually reducing the size of their general epidemiology staffs, and adding duties to those who remain

Florida DOH supports 79 general epidemiology FTEs in CHDs with federal preparedness funds

In some CHDs these are now the majority of epi staffSlide5

Rethinking enteric case investigations

In late 2011, the Epidemiology Bureau started a conversation with CHD staff and state-level foodborne investigation staff

Enteric workgroup

Quality improvement workgroup

Started with a high-level principles document

Then some data analysis

Finally a set of priority recommendations for CHD prioritization of enteric investigations

Separately, we are semi-automating the process for creating cases of salmonellosis in Merlin from electronic laboratory reports (J Hamilton presentation)Slide6

Preparedness implications

At the same time we were operationalizing the PHEP performance measure about ‘time from receipt of case report to initiation of control measures’ for the six priority PHEP diseases

We had decided to add salmonellosis and shigellosis to the PHEP diseases as we built the capacity to capture the information needed for this performance measure

Whether interviewed

Whether investigated

Whether certain control measures were taken, and whenSlide7

High-level principles document (

August 2011)

Key assumption 1:

for these enteric infections, people are most infectious to others while they are ill with

diarrhea

To a first approximation, one’s infectiousness to others should be a function of the number of opportunities to soil one’s hands

S

ome

people shed organisms in stool for days to weeks after they recover from their clinical

illness, but generally the concentration is lower

Key assumption 2: we don’t know about most of the people with these infections (estimated 2% for salmonellosis)Slide8

Purposes of surveillance for these organisms

To detect individual cases in such a way that public health, medical, or behavioral action can prevent spread from the reported

case

To

detect outbreaks of illnesses due to these agents, early enough to make a difference to the course of the

outbreak

To

allow a better understanding of the descriptive epidemiology of

cases

to

be able to focus primary case prevention efforts, and formulate better prevention

strategies

To

detect outbreaks of illnesses due to these

agents

to

understand better the events that lead to outbreaks and thus be able to focus outbreak prevention

effortsSlide9

When can interventions make a difference over one or two incubation periods?

A

case is identified while the person is still ill and presumed infectious, and thus

interventions may

prevent

cases

A

case is identified after illness has resolved, but while the person was recently infectious and is still potentially

infectious

.

Interventions

may still be useful, especially behavior change by

infected contacts,

and prophylactic treatment of

contacts

A

common source outbreak is detected early enough that the source of the outbreak can be removed, changing the course of the

outbreak

An

outbreak that started as a common source outbreak is detected early enough

that there

is still an opportunity to influence the number of cases spread from person to

personSlide10

When can investigations make a longer-term difference?

Even if an

outbreak is detected after the common source is

gone

T

here

is

value

in learning how the outbreak occurred, so that

steps can be taken

to

prevent recurrences, and

to

help guide public health policy (e.g., in relation to regulation, standards, or inspections

)Slide11

Key time parameters

Usual duration of illness was taken from CCDM, picking a number toward the upper end of the usual range

From existing Merlin data, we pulled median time intervals by disease for

Case onset to case report to CHD

Diagnosis to case report to CHD

Specimen collection to case report to CHD

Lab report to case report to CHDSlide12

Reading the table

Agent

Usual duration of illness

(in days)

# of days from onset date

# of days from diagnosis date

# of days from specimen collection date

# of days from lab report date

Campylobacter species

6

6

1

4

1

Cryptosporidium parvum

14

14

8

9

7

Giardia

lamblia

14

14152Salmonella species66141Shigella species99684

If a case report of salmonellosis is received 3 days from specimen collection date, the person is likely still ill.

If a case report of campylobacteriosis is received 7 days from onset date, the person is likely not still ill.Slide13

Our recommended priorities for interview and investigation

Group 1: people whose initial case report indicates they are in a sensitive situation or part of an outbreak.

Group 2: people whose case report is received within the time frames in the table

Group 3: all others

This was conveyed to CHDs March, 2012Slide14

Possible drawbacks

Some outbreaks may come to light only as a consequence of interviewing cases reported one by one, and we might miss outbreaks.

This isn’t the most common way we detect outbreaks

If the cases are interviewed late, the outbreak may have come to light anyway, or ended

Some people who are in sensitive situations will be missed if they are in group 2 and are not interviewed, and we will not be able to keep them out and clear them to return.

If their diarrhea has already resolved, the opportunities for prevention in the sensitive setting are less

Most infectious cases are not detected and reported anyway

We will miss opportunities for education and for generating good-will.Slide15

Let’s look at some data

Cases reported in CY 2011

Only confirmed cases

10,816 cases of 5 diseases

9,028 interviewed (83%)

From September 1 to December 31, 2011, 18% of interviewed cases were interviewed within recommended timeframe (“timely”)

Range from 10% for salmonellosis to 54% for cryptosporidiosisSlide16

Number of confirmed cases > 18 y.o

., proportion where interview would have been recommended*, and reduction in interviews, FL, CY 2011

# of confirmed cases

#

of confirmed

cases actually interviewed

# of cases with

interview recommended*

Theoretical

r

eduction in # of interviews

Campy

1045

768

268

500

Crypto

141

103

106

(3)

Giardiasis

693581195386Salmonellosis238119144941420Shigellosis475392395(3)Total4735375814582300* Based on earliest lab dateSlide17

Number of confirmed cases < 18 y.o

., proportion where interview would have been recommended*, and reduction in interviews, FL, CY 2011

# of confirmed cases

#

of confirmed

cases actually interviewed

# of cases with

interview recommended*

Theoretical

r

eduction in # of interviews

Campy

566

477

114

363

Crypto

61

51

32

19

Giardiasis

536457149308Salmonellosis3,2962,8826322,250Shigellosis1,6221,4031,444(41)Total6,0815,2702,3712,899* Based on earliest lab dateSlide18

Timeliness of interview and diarrhea, for confirmed cases of all five diseases

, FL, March 15 – June 1, 2012

Confirmed,

interviewed 2011 cases

Symptomatic

at interview

Total interviewed

Percent

Interviewed timely

202

486

41.6%

Interviewed late

290

1038

27.9%

Interviewing no-one in Group 3 (late reports) would result in missing about 60% of people with diarrhea at time of interview.

The difference in % with diarrhea by timely interview or not is in the wrong direction for giardiasis.

We may have underestimated duration of diarrhea in giardiasis. People recovering from giardiasis can have prolonged diarrhea even after the organism is eradicated.

32% of interviews timely is increased from 18% in late 2011 Slide19

Separating giardiasis from the other four diseases, March 15 - June 1, 2012

Other four diseases

Symptomatic

at interview

Total interviewed

Percent

Interviewed timely

180

412

43.7%

Interviewed late

244

937

26.0%

Giardiasis

Symptomatic at interview

Total interviewed

Percent

Interviewed timely

22

74

29.7%

Interviewed late

4610145.5%Slide20

Impact on sensitive situations

March 15 – June 2, 2012

Overall

883 adult cases reported, of whom 703 (80%) interviewed

Food handlers:

10 interviewed timely, 9 late

5

symptomatic interviewed timely, 2 late

Healthcare workers

6

interviewed timely, 17 late

5

symptomatic interviewed timely,

4

late

Child care workers

4 interviewed timely,

5

late

2

symptomatic interviewed timely, 5 late

Among 980 cases in children under age 18, for children in child care:

70 interviewed early, 118 late

23 symptomatic interviewed timely, 38 lateSlide21

What are CHDs doing with our recommended priorities?

Survey of CHDs in late April: 29 out of 40 CHDs were adopting the prioritization

Many said they would use the priority list to do only very brief interviews with those in Group

3

% reported as interviewed down from 84% Sept – Dec 2011 (before recommendations made) to 82% March 15 – June 1, 2012.

% of interviews that are timely has gone up from 18% to 32%

% of people symptomatic at time of interview has gone up from 37% to 42%Slide22

Costs and benefits

Following this approach could reduce annual number of interviews completed by over 5000

We would not interview over half of the people who still had diarrhea at the time of interview

We would not identify about half of the adults in sensitive situations who still had diarrhea at time of interview

We would not identify 38% of children in child care who still had diarrhea at time of interview

CHDs are being more selective about whom they

interview (more are timely, more are symptomatic)