Detecting residual chronic Salmonella Typhi carriers on the road to typhoid elimination in Santiago, Chile, 2017-2019.

OBJECTIVES: In Santiago, Chile, where typhoid had been hyperendemic (1977-1991), we investigated whether residual chronic carriers could be detected among household contacts of non-travel-related typhoid cases occurring 2017-2019. METHODS: Culture-confirmed cases were classified as "autochthonous" (domestically-acquired) versus "travel/immigration-related". Household contacts of cases had stool cultures and serum Vi antibody measurements to detect chronic Salmonella Typhi carriers. Whole genome sequences of acute cases and their epidemiologically-linked chronic carrier isolates were compared. RESULTS: Five of 16 autochthonous typhoid cases (31.3%) were linked to four chronic carriers in case households; two cases (onsets 23 months apart) were linked to the same carrier. Carriers were women aged 69-79 years with gallbladder dysfunction and Typhi fecal excretion; three had highly elevated serum anti-Vi titers. Genomic analyses revealed close identity (≤11 core genome SNP [Single Nucleotide Polymorphism] differences) between case and epidemiologically-linked carrier isolates; all were genotypes prevalent in 1980s Santiago. A cluster of four additional autochthonous cases un-linked to a carrier was identified based on genomic identity (0-1 SNPs). Travel/immigration isolate genotypes were typical for the countries of travel/immigration. CONCLUSIONS: Although autochthonous typhoid cases in Santiago are currently rare, 5/16 such cases (31.3%) were linked to elderly chronic carriers identified among household contacts of cases.

Prevalence of pneumococcal bacteremia among children <36 months of age presenting with moderate fever to pediatric emergency rooms of the Metropolitan Region (Santiago), Chile.

Blood culture collection from outpatients < age 36 months with high fever (>40 degrees C, rectal) became a standard of ambulatory care in Emergency Rooms (ERs) of the government Children's Hospitals in Chile's Metropolitan Region (MR) in 1999; thereafter, invasive pneumococcal disease (IPD) incidence doubled over preceding years' estimates limited to hospitalizations. We studied IPD among children with moderate (>39 degrees C but <40 degrees C, rectal) rather than high fever visiting Pediatric ERs. Recruitment ensued Monday to Friday, 1-5 PM, September 1, 2002 through August 31, 2003. Age <36 months; rectal temperature >39 degrees but <40 degrees C; outpatient management; parental consent for hemoculture were inclusion criteria. Thirteen-thousand five hundred seventy-seven children < age 36 months with moderate and 3,214 children with high fever sought ER care. Of 1,134 moderate fever children seen in ERs during the enrollment, parents of 837 consented (73.8%). During these days and hours, 714 children < age 36 months presented with high fever and 651 (91.2%) had a "routine" blood culture. Pneumococcemia was detected among 0.7% with moderate and 1.2% with high fever (6/837 vs 8/651, p > 0.05). Extrapolating these rates to all ER outpatients < age 36 months with moderate and high fever, we estimate the true burden as 95 and 39 cases, respectively. The burden of pediatric IPD in the MR is currently underestimated because bacteremias among ER outpatients with moderate fever are not detected. If blood cultures were systematically collected from outpatients with moderate fever, recorded pediatric IPD burden would rise >2-fold. However, economic and logistical constraints preclude such a practice.