Testing for Norwalk-like viruses at the State Health
Department Level: A Valuable Tool for Identifying the Agent for
Gastroenteritis Outbreaks
L EDWARDS, D SHAH, K FUJII, J TOTARO,
N BARKER, J ABBOTT, J CHEN, R MYERS.
Maryland Department of Health and Mental Hygiene, Baltimore, Maryland
Background: Gastroenteritis (GE) represents approximately
two-thirds of all the communicable disease outbreaks reported in
Maryland each year, yet the causative agent is not identified for
a majority of these outbreaks. In January 2002, the Maryland Department
of Health and Mental Hygiene (DHMH) began testing stool specimens
for Norwalk-like viruses (NLVs) at the state health department laboratory.
This evaluation was done in order to indicate the usefulness of
NLV testing in Maryland.
Methods: All GE outbreaks reported in Maryland
from January 1 – March 31, 2002 were compared to GE outbreaks
reported from January 1 – March 31 of 1999, 2000, and 2001,
respectively. Laboratory samples collected and testing results were
reviewed.
Results: During the first three months of 2002,
stools were tested for Norwalk-like viruses in 23 (31%) of gastroenteritis
outbreaks. NLV was identified in 17 (74%) of outbreaks in which
testing was attempted. This includes lab confirmation for 11 (73%)
GE outbreaks at nursing homes in which person-to-person transmission
was suspected, 3 (75%) foodborne GE outbreaks, and 3 (75%) GE outbreaks
in other settings. Compare these figures to outbreaks during the
same three months in 1999 – 2001 in which NLV was identified
in an average of only 4 outbreaks each year (range= 2 - 6). NLV
was isolated in 13 of 24 (57%) of GE outbreaks in which testing
was offered.
Conclusions: Prior to implementation of testing
for NLVs at the Maryland State Health Department, the causative
agent for a majority of GE outbreaks had remained unknown. Testing
for NLVs at the state level has helped Maryland identify Norwalk-like
viruses as the agent for a majority of the GE outbreaks in which
NLV testing was attempted. States that do not have the ability to
test for NLV at the state level may want to consider offering this
testing capability at their state laboratory.
Maryland Department of
Health & Mental Hygiene — Epidemiology & Disease Control
Program |
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