Infective SARS-CoV-2 in Skull Sawdust at Autopsy, Finland

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Abstract

A study was conducted to assess the distribution of SARS-CoV-2 at autopsy in 22 deceased persons with confirmed COVID-19. SARS-CoV-2 was identified by PCR in 9.1% of cases and by culture in 4.5% of cases in skull sawdust, suggesting the presence of live virus in tissues postmortem, including bone. The occupational exposure risk remains low with the use of appropriate personal protective equipment (PPE).


Introduction

The COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has necessitated a closer examination of virus transmission and persistence in different environments, including postmortem settings. Autopsies, which allow simultaneous access to all body tissues and compartments, provide a unique opportunity for extensive sampling and research into SARS-CoV-2 distribution. Despite the initial hesitancy in conducting autopsies early in the pandemic due to transmission risks and PPE shortages, the importance of such procedures has been increasingly recognized for understanding the pathology and epidemiology of COVID-19.

Autopsies, however, pose an occupational hazard, particularly in the context of airborne pathogens. For instance, Mycobacterium tuberculosis is known to significantly increase the risk of infection for pathologists conducting autopsies. Similarly, viable SARS-CoV-2 has been detected in tissues long after death from COVID-19. This study explores the presence of SARS-CoV-2 in skull sawdust, a byproduct of skull sawing during autopsy, to determine the potential risks and necessary precautions for personnel involved in autopsy procedures.


Methodology

The study was part of the Clin_COVID-19 master study, approved by the Helsinki University Hospital Ethics Committee (approval no. HUS/1238/2020). All autopsies were clinical (nonforensic) and conducted in compliance with Finnish research laws and regulations, with consent from the next of kin. The postmortem examinations took place in the pathology department of the HUS Diagnostic Center in Meilahti, Helsinki, Finland. The study included 22 PCR-confirmed COVID-19 cases identified during 2021–2022, with skull sawdust samples taken during autopsy.

Autopsies included neuropathological examinations and the collection of swabs and fresh tissues from various body sites, including airway, nonairway, and central nervous system (CNS) categories. Skull sawdust and samples from the contaminated autopsy table were also collected. PCR-positive samples were cultured using VeroE6 cells to determine the presence of infective SARS-CoV-2.


Results

SARS-CoV-2 was detected by reverse transcription PCR in 100% of airway samples, 45.5% of nonairway samples, 0% of CNS samples, 9.1% of skull sawdust samples, and 59.1% of autopsy table samples. The virus was culturable in 59.1% of airway samples, 9.1% of nonairway samples, 4.5% of skull sawdust samples, and 13.6% of autopsy table samples.

No occupational cases of COVID-19 were identified among the personnel involved in the autopsy procedures. Serologic screening and PCR testing of all personnel (n=5) involved in COVID-19 autopsies in June 2020 were negative.


Discussion

The findings revealed that SARS-CoV-2 was detectable by PCR in 9.1% of skull sawdust samples and by viral culture in 4.5% of these samples. This indicates that live virus can be present in postmortem bone tissues, including the skull, posing a potential risk of aerosolized infective viruses during autopsy procedures involving skull sawing. These results align with previous studies showing SARS-CoV-2 PCR positivity on autopsy equipment, although no previous work specifically examined cranial sawdust for pathogens.

The sample size was limited but represented a consecutive, nonselected series of cases from a single institution. While aerosols were not directly assessed, the use of high-energy techniques like bone sawing is known to generate aerosols. The absence of CNS contamination suggests the sterility of the sampling technique used, reducing the likelihood of other contamination sources in the skull sawdust samples.


Conclusion

The study underscores the importance of stringent safety measures during autopsy procedures, particularly those involving bone sawing, to mitigate the risk of occupational infections. While the general safety measures employed appear adequate for most pathogens, including SARS-CoV-2, early testing for pathogens in skull sawdust and other tissues could further enhance safety during pandemics.

Pandemic preparedness should include plans for early, rapid autopsies to gather vital data, ensuring that health personnel are protected through appropriate PPE and safety protocols. This approach will be crucial for managing future outbreaks and understanding the pathology of emerging infectious diseases.


Acknowledgements

The authors extend their gratitude to the staff of the pathology department at the HUS Diagnostic Center for their assistance with the autopsies and sample collections. Special thanks are also due to the Helsinki University Hospital Ethics Committee for their guidance and approval of the study.


Further Research Directions

The detection of live SARS-CoV-2 in skull sawdust opens several avenues for further research. Future studies could focus on the following:

  • Quantitative Analysis: Detailed quantitative studies to measure the viral load in various tissues, including bone, to understand the extent of SARS-CoV-2 persistence postmortem.
  • Aerosolization Studies: Experimental studies to directly measure the generation of aerosols during skull sawing and other high-energy autopsy procedures, and to assess the viability of SARS-CoV-2 in these aerosols.
  • Comparative Pathogen Studies: Comparative studies on the presence and viability of other pathogens in autopsy-derived aerosols, particularly in bones, to develop broader safety protocols for autopsies.
  • Longitudinal Studies: Longitudinal studies to track the presence of SARS-CoV-2 in postmortem tissues over time, to understand how long the virus remains viable and infectious after death.
  • PPE Efficacy: Studies on the efficacy of different types of PPE in protecting against exposure to SARS-CoV-2 and other pathogens during autopsies, particularly those involving high-risk procedures like skull sawing.

By addressing these research directions, the medical community can enhance the understanding of SARS-CoV-2 transmission risks in autopsy settings and improve safety protocols to protect health personnel.


reference link : https://wwwnc.cdc.gov/eid/article/30/8/24-0145_article

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