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ISDS Annual Conference Proceedings 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution,
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ISDS 2018 Conference Abstracts
Evaluation of Syndromic Surveillance in Detecting
Hepatitis A in Los Angeles County
Michael Lim*, Emily Kajita and Bessie Hwang
Public Health, Los Angeles County, Los Angeles, CA, USA
Objective
To create a hepatitis A virus (HAV) syndrome category with which
to monitor emergency department (ED) visits for situational awareness
during a currently emerging Hepatitis A community outbreak in Los
Angeles County (LAC), and to evaluate its usefulness.
Introduction
In early 2017, HAV outbreaks were identified in San Diego County
(490 cases)1 and Santa Cruz County (73 cases)2 in California, affecting
primarily the homeless and/or illicit drug users. As of October 10,
2017, LAC had identified 12 outbreak-related HAV cases. Due to
LAC’s proximity to San Diego County, and its own large homeless
population, the syndromic surveillance team of the LAC Department
of Public Health created a syndrome category and began querying its
ED data to monitor for any increase in HAV-related visits.
Methods
ED data from 1/1/2017 to 10/10/2017 (CDC weeks 1-41) from
all participating syndromic EDs in LAC were queried for patients
who reported symptoms and signs of HAV. For comparison, ED data
from calendar year 2016 was also queried. The query consisted of
key word searches primarily within the chief complaint field, and, if
available, the diagnosis and triage note fields. Based on the Centers
for Disease Control and Prevention (CDC) clinical description of
hepatitis A3, the HAV syndrome category was defined as: jaundice
(or elevated liver function tests) AND nausea or vomiting. Any ED
visit that mentioned a diagnosis of hepatitis A also met the syndrome
criteria. The resulting line lists were reviewed, and the query was
periodically refined to exclude visits unrelated to hepatitis A (e.g.,
previous history of or vaccination for hepatitis A, other forms of
hepatitis, and neonatal jaundice). The syndromic system was also
queried for records that matched the 12 LAC cases by hospital and
admission date. In addition, the chief complaint, diagnosis, and
triage note fields were reviewed for any mention of homelessness or
intravenous drug use.
Results
The syndromic system detected 158 ED patients meeting the HAV
syndrome category criteria. Of these, 12.7% had a diagnosis of HAV,
53.8% had jaundice, 36.7% had elevated liver enzymes, 65.2% had
nausea, and 65.8% had vomiting. In 2016, 170 ED patients who met
the syndrome criteria were detected: 8.2% had a diagnosis of HAV,
64.1% had jaundice, 32.4% had elevated liver enzymes, 63.5% had
nausea, and 71.2% had vomiting. In both years, no indications of
homelessness or IDU were found.
Of the 12 LAC confirmed HAV outbreak-related cases, three did
not go to a hospital, and thus did not have any syndromic data. Two
went to non-participating syndromic EDs, but medical chart review
showed that they would not have met the syndrome criteria. Of the
remaining seven, all went to a participating syndromic ED, and three
met the syndrome criteria, but none had any mention of homelessness
or IDU.
Conclusions
No major change was seen in the trend of HAV syndrome visits
in 2017 compared to 2016 (Figure 1). One of the challenges in
monitoring HAV incidence is that the clinical signs and symptoms
are very general, and may be shared with many other conditions. An
emerging outbreak may not be detected above background levels
unless the increase in ED patients with HAV is large, or consolidated
over time. Variability in data quality in the free text fields such as
chief complaint and triage notes may be problematic. Cases will be
missed if data fields are not fully and accurately documented, and
also if patients didn’t go to a participating syndromic hospital, or
to a hospital at all. Though many syndromic hospitals now report
diagnosis information, such information may be delayed, waiting for
lab results. Using a stricter syndrome definition, such as requiring
a specific diagnosis of HAV, may result in underreporting, but
may provide a more accurate baseline for detecting increases and
monitoring trends.
While the query relied primarily on ED chief complaint, diagnosis
and triage notes also proved useful in detecting HAV syndrome visits.
None of the confirmed HAV cases that were known to be homeless
had any mention of homelessness. The lack of any records indicating
homelessness or IDU may indicate that these conditions are not
currently reliably captured in the syndromic extract of ED patient
records.
LAC will continue to monitor for increases in HAV syndrome
ED visits as a surrogate measure of HAV spread in the community.
Syndromic surveillance, despite its limitations, remains a valuable
complement to electronic lab reporting and other traditional reporting
mechanisms.
Figure 1. Proportion trend graph of HAV syndrome ED visits.
Keywords
syndromic surveillance; hepatitis A; homeless
ISDS Annual Conference Proceedings 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution-
Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/), permitting all non-commercial use, distribution,
and reproduction in any medium, provided the original work is properly cited.
ISDS 2018 Conference Abstracts
References
1. San Diego Hepatitis A Outbreak, 2017 [Internet]. San Diego, CA: San
Diego County Health & Human Services Agency [cited 2017 Sep 21].
Available from: http://www.sandiegocounty.gov/content/sdc/hhsa/
programs/phs/community_epidemiology/dc/Hepatitis_A.html
2. Santa Cruz Hepatitis A, 2017 [Internet]. Santa Cruz, CA: County of
Santa Cruz Health Services Agency [cited 2017 Sep 21]. Available
from: http://www.santacruzhealth.org/HSAHome/HSADivisions/
PublicHealth/CommunicableDiseaseControl/HepatitisA.aspx
3. Hepatitis A, Acute 2012 Case Definition [Internet]. Atlanta, GA:
Centers for Disease Control and Prevention National Notifiable
Diseases Surveillance System [cited 2017 Sep 21]. Available
from:https://wwwn.cdc.gov/nndss/conditions/hepatitis-a-acute/case-
definition/2012/
*Michael Lim
E-mail: milim@ph.lacounty.gov
Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 10(1):e121, 2018