480. Detecting Hidden Outbreaks of Domestically-Acquired Typhoid Fever United States, 19992010
Session: Poster Abstract Session: Public Health
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Posters
  • DomTypIDweekPoster_0920.pdf (621.6 kB)
  • Background:

    Typhoid fever (TF) is transmitted by ingestion of food or water contaminated with Salmonella enterica serotype Typhi (Typhi) from an infected person. Outbreaks may be caused by asymptomatic carriers who shed the bacterium sporadically over many years. Detection and investigation of TF outbreaks among apparently sporadic cases offer opportunities to identify and treat chronic carriers and prevent illnesses. 

    Methods:

    Domestically-acquired typhoid fever (DATF) was defined as a compatible illness in a person with culture-confirmed Typhi infection who denied foreign travel during the 30 days before illness onset. We searched the National Typhoid Fever Surveillance database for DATF cases and identified their isolates in the National Antimicrobial Resistance Monitoring System and PulseNet, the national molecular subtyping database. Using a space-time scan statistic software (SaTScanTM), we identified clusters of ≥2 DATF cases. Based on reports of DATF outbreaks in the literature and Foodborne Disease Outbreak Surveillance System, and subtyping and epidemiologic data from state health departments, we classified clusters as outbreaks (common exposure identified), non-outbreaks (common exposure unlikely), or possible outbreaks (insufficient data).

    Results:

    DATF accounted for 610 (18%) of 3,373 TF cases with known travel status during 1999­–2010; 71% (412/579) of DATF patients were hospitalized. Compared to isolates from TF cases with foreign travel history, DATF isolates were less often multidrug-resistant (15% vs. 2%). We identified 28 outbreaks, 17 non-outbreaks, and 2 possible outbreaks within 45 space-time clusters. Sixteen outbreaks were linked to a confirmed or suspected carrier, two were linked to imported frozen fruits, one was linked to Gulf Coast oysters, and five occurred among ≥2 household contacts with an unknown source. The number of epidemiologically linked cases in these outbreaks ranged from 2–15 (median=2).

    Conclusion:

    Small outbreaks of typhoid fever continue to occur in the United States. Space-time scan statistic is a promising novel screening tool for detecting DATF outbreaks. However, molecular subtyping and shoe-leather epidemiology are still needed to confirm outbreaks and identify carriers.

    Maho Imanishi, VMD, MPH1, Anna Newton, MPH2, Gladys Gonzalez-Aviles, MS2, Magdalena Kendall, MPH3, Karunya Manikonda, MPH2, Nikki Maxwell, MSPH2, Jessica Halpin, MS2, Molly Freeman, PhD2, Tracy Ayers, MS2, Gordana Derado, PhD2, Barbara E. Mahon, MD, MPH2, Antonio R. Vieira, DVM, PhD, MPH2 and Eric D. Mintz, MD, MPH2, (1)Division of Foodborne, Waterborne, and Environmental Diseases, Centers for Disease Control and Prevention, Atlanta, GA, (2)Centers for Disease Control and Prevention, Atlanta, GA, (3)Division of Foodborne, Waterborne, and Environmental Diseases, CDC, Atlanta, GA

    Disclosures:

    M. Imanishi, None

    A. Newton, None

    G. Gonzalez-Aviles, None

    M. Kendall, None

    K. Manikonda, None

    N. Maxwell, None

    J. Halpin, None

    M. Freeman, None

    T. Ayers, None

    G. Derado, None

    B. E. Mahon, None

    A. R. Vieira, None

    E. D. Mintz, None

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