Japanese study validates viral persistence of infectious SARS-CoV-2 in patient cadavers.
The study findings were published in the peer reviewed International Journal Of Infectious Diseases.
• Infectious SARS-CoV-2 remained in 55% (6/11) corpses and 43% (13/30) specimens.
• The highest infectious titer was 2.09E + 06 plaque-forming units/g in corpse lung tissue.
• The time from death to discovery was 0-1 day in all cases with the infectious virus.
• The longest postmortem interval with virus infectivity was 13 days (12 days refrigerated).
• The status of the corpse influences SARS-CoV-2 infectivity.
Here, we determined the amount of virus in corpses of patients with COVID-19 and found that the infectious virus was present in large amounts (up to 2.09E + 06 PFU/g) in corpse lung tissue and in refrigerated corpses even 13 days after death.
Grassi et al. reported that of 29 PCR-positive autopsy cases using postmortem nasopharyngeal swabs, viral mRNA was detected in seven of 22 posthospitalization deaths and six of seven nonhospitalization deaths [].
Similar to previous reports [,], our findings indicate that individuals involved in autopsies or examinations of corpses must consider the risk of infection with SARS-CoV-2 and take measures to protect themselves from infection to reduce that risk. Our findings are crucial for public health worldwide.
In our analysis, there were no statistically significant differences in viral genomic copy number (100,000 copies/µl) or infectivity in either the nasopharynx or lungs. However, when the viral copy number in the nasopharyngeal swabs was less than 100,000 copies/µl (Table 3), the infectious virus was not detected.
Previously, it has been reported that there is a statistically significant difference between the minimum cycle threshold value of RNA and the presence of viral mRNA []. We plan to further examine the relationship between viral genomic copy number and infectivity.
The viral genomic copy number for case 1 was very low, as shown in Table 2. In this case, a large mass (about 3 × 3 × 3 cm3) was collected from the lung during autopsy. The specimen was then frozen at -80°C and the mass was subsequently thawed when the RNA was extracted.
Although the lung used for extraction weighed approximately 10 mg, it is possible that the viral mRNA was degraded when the specimen was thawed. In addition, because this was a case of drowning in a pond the day after discharge from the hospital, it is possible that the viral genomic copy number was not measured accurately due to the condition of the lungs.
When examining the infectious titer of the virus, it is important to consider various factors, such as the timing of specimen collection, collection method, specimen storage method, and use of culture medium for transport, etc. In the future, we plan to examine conditions related to specimen collection for such emerging infectious diseases.
In our study, the infectious viruses were detected when the diagnosis date was within 4 days of the date of death and the body had not yet decomposed. Infectious viruses were also detected when the discovery date was within 1 day of the date of death. There appears to be a state in which the virus survives in the early stages of infection when the host’s life has been terminated and the virus remains infectious.
Infectious viruses were also detected when the refrigeration period was as long as 12 days, consistent with previous reports [,]. In our limited number of samples, we found that when death occurs because of rapidly worsening COVID-19 symptoms or within a short period after SARS-CoV-2 infection, the probability that infectious virus remains in the corpse is high.
If antemortem information is not available, postmortem SARS-CoV-2 PCR testing should be performed. If SARS-CoV-2 PCR-positive corpses are found within a few days after death and they are kept in a cold environment, they should be handled with caution due to likely presence of the infectious virus.
When COVID-19 first began to spread, different countries published their own guidelines for the handling of cadavers [], but autopsies of bodies infected or suspected of being infected with SARS-CoV-2 should be performed in accordance with the postmortem guidance of the World Health Organization [] and the Centers for Disease Control and Prevention [].
In our study, the titer in lung tissue was higher than that in the nasopharyngeal swab fluid. Therefore, great care should be taken when handling the lungs during autopsy and formalin fixation should be performed immediately. Also, appropriate infection control measures should be implemented during the entire funeral and burial processes to protect the workers handling corpses.
To this end, ensuring that all those involved in the handling corpses are promptly provided with the necessary supplies for infection protection is critical. Furthermore, measures, such as prioritizing vaccination, in this population of workers should be considered.