Automated use of WHONET and SaTScan to detect outbreaks of Shigella spp. using antimicrobial resistance phenotypes

Abstract

Antimicrobial resistance is a priority emerging public health threat, and the ability to detect promptly outbreaks caused by resistant pathogens is critical for resistance containment and disease control efforts. We describe and evaluate the use of an electronic laboratory data system (WHONET) and a space-time permutation scan statistic for semi-automated disease outbreak detection. In collaboration with WHONET-Argentina, the national network for surveillance of antimicrobial resistance, we applied the system to the detection of local and regional outbreaks of Shigella spp. We searched for clusters on the basis of genus, species, and resistance phenotype and identified 19 statistical 'events' in a 12-month period. Of the six known outbreaks reported to the Ministry of Health, four had good or suggestive agreement with SaTScan-detected events. The most discriminating analyses were those involving resistance phenotypes. Electronic laboratory-based disease surveillance incorporating statistical cluster detection methods can enhance infectious disease outbreak detection and response.

Fig. 1

Geographic distribution of laboratories in the Collaborative Group WHONET-Argentina. The 38 laboratories included in the analyses of this paper are indicated with a solid circle (●), while others are indicated with an open diamond (◇). BA, Buenos Aires (province), CA, Catamarca, CB, Chubut, CD, Córdoba, CH, Chaco, CR, Corrientes, DF, Buenos Aires (federal capital), ER, Entre Ríos, FO, Formosa, LP, La Pampa, LR, La Rioja, MD, Mendoza, MI, Misiones, NE, Neuquén, PJ, Jujuy, RN, Río Negro, SA, Salta, SC, Santa Cruz, SE, Santiago del Estero, SF, Santa Fe, SJ, San Juan, SL, San Luis, TF, Tierra del Fuego, TU, Tucumán.

Fig. 2

Frequency distribution of S. sonnei isolates non-susceptible to SXT by week for the laboratory in La Pampa associated with event 5. Isolates contributing to the SaTScan event are indicated by solid bars.

Fig. 3

Location of outbreaks reported to the Ministry of Health (A–E) and statistical ‘events’ detected by SaTScan (1–19), July 2006–June 2007.

Fig. 4

Frequency distribution of Shigella spp. isolates included in the analyses by month July 2005 to November 2006 (n=29 laboratories) ; January 2006 to December 2007 (n=38 laboratories).