VIENNA – Widespread foodborne infectious-disease outbreaks pose the greatest challenge for detection, according to an analysis of 101 U.S. outbreaks during 1998-2008.
Two U.S. Salmonella outbreaks took 492 days and 251 days to detect, respectively, by far the longest lag from onset to detection of any of the outbreaks analyzed, said Heather Allen, Ph.D., at the International Meeting on Emerging Diseases and Surveillance.
In contrast, the entire group of 101 human or animal outbreaks during 1998-2008 with data available for analysis took a median 13 days to detect, and a mean 32 days, with more than three quarters of the outbreaks detected within 50 days, reported Dr. Allen, a public health analyst with LMI, a consulting company in McLean, Va. The results Dr. Allen reported came from a study she ran before becoming an LMI employee.
Median time to detection among outbreaks that extended beyond a single U.S. region was 35 days, compared with medians of 8-11 days for outbreaks confined to a single U.S. region (Northeast, Midwest, South, or West).
In cases of widespread foodborne outbreaks, "the cases trickle in and take a while for the number to build to where it is detected," Dr. Allen said.
The slow lag to report some foodborne U.S. outbreaks occurred despite use of best practices in those episodes, including PulseNet, a network of public health and food regulatory labs coordinated by the Centers for Disease Control and Prevention that apply molecular fingerprinting to isolates of Escherichia coli, Salmonella, and other foodborne pathogens.
Dr. Heather Allen
Factors that may decrease reporting of infections and delay outbreak detection include awareness of the need to report, how busy practitioners are, the ease of reporting, and privacy concerns of patients or animal owners. The delay between a positive infection result and reporting it to a state or federal agent can be significant, and results in large differences in response times, Dr. Allen said in an interview.
"All human disease reporting to the federal level is voluntary; reporting to the state is governed by state laws and regulations."
Published records from sources such as Morbidity and Mortality Weekly Report and ProMED-Mail included 440 outbreaks during 1998-2008; Dr. Allen had data for analysis from 101 of these outbreaks. About two-thirds were in people, 16% in domestic animals, and 18% in people and animals. Initial reporting of the outbreak by a laboratory happened in 46% of the episodes, practitioners gave the initial report for 34%, and state agencies first reported 20%. State agencies had the longest average delay, 29 days, compared with roughly 10 days when either practitioners or labs made the first report.
Dr. Allen had no disclosures.
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