Human Streptococcus suis outbreak, Sichuan, China

Abstract

From mid-July to the end of August 2005, a total of 215 cases of human Streptococcus suis infections, 66 of which were laboratory confirmed, were reported in Sichuan, China. All infections occurred in backyard farmers who were directly exposed to infection during the slaughtering process of pigs that had died of unknown causes or been killed for food because they were ill. Sixty-one (28%) of the farmers had streptococcal toxic shock syndrome; 38 (62%) of them died. The other illnesses reported were sepsis (24%) and meningitis (48%) or both. All isolates tested positive for genes for tuf, species-specific 16S rRNA, cps2J, mrp, ef, and sly. A single strain of S. suis caused the outbreak, as shown by the identification of a single ribotype. The high death ratio was of concern; prohibiting backyard slaughtering ended the outbreak.

Figure 1

Epidemic curve showing the dates of onset for 215 human cases of Streptococcus suis infection, Sichuan, China (as of August 18, 2005).

Figure 2

Suspected cases of meningococcal meningitis in the 12 affected prefectures in Sichuan.

Figure 3

Geographic distribution of Streptococcus suis cases in Sichuan Province, China, relating to (A) all reports, and (B) 66 laboratory-confirmed cases alone (as of August 18, 2005).

Figure 4

Photograph of a Streptococcus suis patient's legs with streptococcal toxic shock syndrome, featuring purpura and evidence of gangrenous changes in the calf extending down to the foot.

Figure 5

Ribotyping of Streptococcus suis serotype 2 isolates by PvuII restriction. Lane 1, deceased pig isolate SC5; lane 2, deceased pig isolate SC16; lane 3, patient isolate SC154; lane 4, patient isolate SC160; lane 5, patient isolate SC175; lane 6, patient isolate SC179; lane 7, patient isolate SC204; lane 8, patient isolate SC206; M, molecular size standard.