First Description of a Yersinia pseudotuberculosis Clonal Outbreak in France, Confirmed Using a New Core Genome Multilocus Sequence Typing Method.

Yersinia pseudotuberculosis is an enteric pathogen causing mild enteritis that can lead to mesenteric adenitis in children and septicemia in elderly patients. Most cases are sporadic, but outbreaks have already been described in different countries. We report for the first time a Y. pseudotuberculosis clonal outbreak in France, that occurred in 2020. An epidemiological investigation based on food queries pointed toward the consumption of tomatoes as the suspected source of infection. The Yersinia National Reference Laboratory (YNRL) developed a new cgMLST scheme with 1,921 genes specific to Y. pseudotuberculosis that identified the clustering of isolates associated with the outbreak and allowed to perform molecular typing in real time. In addition, this method allowed to retrospectively identify isolates belonging to this cluster from earlier in 2020. This method, which does not require specific bioinformatic skills, is now used systematically at the YNRL and proves to display an excellent discriminatory power and is available to the scientific community. IMPORTANCE We describe in here a novel core-genome MLST method that allowed to identify in real time, and for the first time in France, a Y. pseudotuberculosis clonal outbreak that took place during the summer 2020 in Corsica. Our method allows to support epidemiological and microbiological investigations to establish a link between patients infected with closely associated Y. pseudotuberculosis isolates, and to identify the potential source of infection. In addition, we made this method available for the scientific community.

Epidemiology and viral etiology of the influenza-like illness in corsica during the 2012-2013 Winter: an analysis of several sentinel surveillance systems.

Influenza-like illness (ILI) surveillance is important to identify circulating and emerging/reemerging strains and unusual epidemiological trends. The present study aimed to give an accurate picture of the 2012-2013 ILI outbreak in Corsica by combining data from several surveillance systems: general practice, emergency general practice, hospital emergency units, intensive care units, and nursing homes. Twenty-eight respiratory viruses were retrospectively investigated from patients in general practice with ILI. Sequence analysis of the genetic changes in the hemagglutinin gene of influenza viruses (A(H1N1)pdm2009, A(H3N2) and B) was performed. The trends in ILI/influenza consultation rates and the relative illness ratios (RIRs) of having an ILI consultation were estimated by age group for the different surveillance systems analyzed. Of the 182 ILI patients enrolled by general practitioners, 57.7% tested positive for influenza viruses. Phylogenetic analyses suggested a genetic drift for influenza B and A(H3N2) viruses. The ILI/influenza surveillance systems showed similar trends and were well correlated. In accordance with virological data, the RIRs of having an ILI consultation were highest among the young (<15 years old) and decreased with age. No clusters of acute respiratory illness were declared by the sentinel nursing homes. This study is noteworthy in that it is the first extensive description of the 2012-2013 ILI outbreak in Corsica as monitored through several surveillance systems. To improve ILI surveillance in Corsica, a consortium that links together the complementary regional surveillance ILI systems described here is being implemented.