Metaviromics Study on Populations in Areas Affected by Unexplained Sudden Death in Yunnan Province

Abstract

Objective: To investigate the correlation between the occurrences of unexplained sudden death in Yunnan Province and the pathogen spectrum by using real-time fluorescent quantitative reverse transcription PCR, metagenomic next-generation sequencing (mNGS), and virus isolation techniques to test autopsy samples from cases of unexplained sudden death and fecal specimens from populations in affected areas. Methods: Real-time fluorescent quantitative reverse transcription PCR and Sanger sequencing were performed on 101 fecal samples collected from populations in affected areas. Virus isolation was conducted on fecal and gastric content samples from individuals who died suddenly. Additionally, metavirome sequencing and pathogen spectrum abundance detection were performed on 50 autopsy organ samples. Results: No specific fragments of enteroviruses were detected in 101 fecal samples from the population in the affected wards, and no viruses were isolated from fecal and gastric content samples of sudden death victims. Among the 50 autopsy organ samples, 29 were successfully sequenced. High-throughput sequencing revealed low-abundance enterovirus reads in 11 samples (relative abundance ≤ 0.91% in all cases); Enterovirus A114 was detected in 6 samples (with relative abundances of 0.211%, 0.571%, 0.910%, 0.013%, 0.002%, and 0.0000263%, respectively); Coxsackievirus A2 in 9 samples (with relative abundances of 0.111%, 0.192%, 0.051%, 0.291%, 0.007%, 0.00019%, 0.00342%, 0.000551%, and 0.0000368%, respectively); and Coxsackievirus B3 in 9 samples (with relative abundances of 0.312%, 0.486%, 0.120%, 0.765%, 0.001%, 0.001%, 0.001%, 0.0000999%, and 0.00000848%, respectively). Coexistence of 2-3 types of enteroviruses was observed in some samples. Genomic annotation results indicated that high-abundance bacteria were primarily Paeniclostridium sordellii and Escherichia coli, while viral species could not be successfully assembled due to their low abundance. Conclusion: Enterovirus infection may be one of the causes of some unexplained sudden deaths in Yunnan, and the possibility of varying degrees of enterovirus infection cannot be ruled out in some populations in the affected areas. The detection of bacteria may be attributed to the normal intestinal flora of the human body or contamination during the autopsy sampling process.