Plague Outbreak of a Family Emerging from Hibernation.

In April 2021, a plague outbreak was identified within one family shortly after emerging from hibernation, during plague surveillance in the plague foci of the Qinghai-Tibet Plateau. A total of five marmots were found dead of near the same burrow; one live marmot was positive of fraction 1 (F1) antibody. Comparative genome analysis shows that few single nucleotide polymorphisms were detected among the nine strains, indicating the same origin of the outbreak. The survived marmot shows a high titer of F1 antibody, higher than the mean titer of all marmots during the 2021 monitoring period ( = 391.00,  = 2.81,  < 0.01). Marmots live with during hibernation when the pathogen is inhibited by hypothermia. But they wake up during or just after hibernation with body temperature rising to 37°C, when goes through optimal growth temperature, increases virulence, and causes death in marmots. A previous report has shown human plague cases caused by excavating marmots during winter; combined, this study shows the high risk of hibernation marmot carrying . This analysis provides new insights into the transmission of the highly virulent in plague foci and drives further effort upon plague control during hibernation.