Reemergence of human plague in Yunnan, China in 2016

Area of Science:

• Microbiology
• Epidemiology
• Genetics

Background:

• The third plague pandemic originated in Yunnan, China, with the last human epidemic from 1986-2005.
• A human plague case in 2016 marked the reemergence of the disease after a decade-long silent period.
• Rattus flavipectus rats were identified as the primary reservoir for plague in the Xishuangbanna Prefecture.

Purpose of the Study:

• To investigate the molecular characteristics of Yersinia pestis strains isolated during the 2016 plague reemergence in Yunnan.
• To compare these strains with previously identified Y. pestis isolates from Yunnan and adjacent regions.

Main Methods:

• Utilized three molecular typing techniques: Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) analysis, Different Region analysis (DFR), and Multiple-Locus Variable Number of Tandem Repeats analysis (MLVA).
• Analyzed Y. pestis strains isolated from a human case and a host animal in 2016.
• Compared 2016 isolates with historical strains from the Rattus flavipectus plague focus and surrounding provinces.

Main Results:

• DFR profiles of the 2016 Yunnan strains matched previous isolates from the Rattus flavipectus focus.
• A specific spacer (c3) found in earlier strains was absent in the 2016 Ypc CRISPR loci.
• MLVA (14+12) analysis indicated that the 2016 strains exhibited different molecular patterns compared to historical isolates from Yunnan and adjacent provinces.

Conclusions:

• The molecular data suggests a potential new introduction or significant genetic shift in Yersinia pestis within the Yunnan plague reservoir.
• Plague reemergence in Yunnan warrants continued surveillance and molecular characterization of circulating Y. pestis strains.