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BackgroundThe prolonged presence of infectious severe acute respiratory syndrome coronavirus (SARS-CoV-2) in deceased coronavirus disease 2019 (COVID-19) patients has been reported. However, infectious virus titers have not been determined. Such information is important for public health, death investigation, and handling corpses.AimThe aim of this study was to assess the level of SARS-CoV-2 infectivity in COVID-19 corpses.MethodsWe collected 11 nasopharyngeal swabs and 19 lung tissue specimens from 11 autopsy cases with COVID-19 in 2021. We then investigated the viral genomic copy number by real-time reverse transcription-polymerase chain reaction and infectious titers by cell culture and virus isolation.ResultsInfectious virus was present in 6 of 11 (55%) cases, 4 of 11 (36%) nasopharyngeal swabs, and 9 of 19 (47%) lung specimens. The virus titers ranged from 6.00E + 01 plaque-forming units (PFU)/mL to 2.09E + 06 PFU/g. In all cases in which an infectious virus was found, the time from death to discovery was within 1 day and the longest postmortem interval was 13 days.ConclusionCOVID-19 corpses may have high titers of infectious virus after a long postmortem interval (up to 13 days). Therefore, appropriate infection control measures must be taken when handling corpses.

Although it has been 2.5 years since the COVID-19 pandemic began, the transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from a dead infected body remains unclear, and often, in Japan bereaved family members are not allowed to view in-person a loved one who has died from COVID-19. In this study, we analyzed the possibility of SARS-CoV-2 transmission from a dead body by using the hamster model. We also analyzed the effect of Angel-care––in which the pharynx, nostril, and rectum are plugged––and embalming on reducing transmissibility from dead bodies. We found that SARS-CoV-2 could be transmitted from the body of animals that died within a few days of infection; however, Angel-care and embalming were effective in preventing transmission from the dead body. These results suggest that protection from infection is essential when in contact with a SARS-CoV-2-infected dead body, and that sealing the cavities of a dead body is an important infection control step if embalming is not done.ImportanceWe found that SARS-CoV-2 could be transmitted from a dead body presumably via postmortem gases. However, we also found that postmortem care, such as plugging the pharynx, nostrils, and rectum, or embalming could prevent transmission from the dead body. These results indicate that protection from infection is essential when handling infected corpses, and that appropriate care of SARS-CoV-2-infected corpses is important.

The prevalence of the Omicron subvariant BA.2.75 is rapidly increasing in India and Nepal. In addition, BA.2.75 has been detected in at least 34 other countries and is spreading globally. However, the virological features of BA.2.75 are largely unknown. Here, we evaluated the replicative ability and pathogenicity of BA.2.75 clinical isolates in Syrian hamsters. Although we found no substantial differences in weight change among hamsters infected with BA.2, BA.5, or BA.2.75, the replicative ability of BA.2.75 in the lungs was higher than that of BA.2 and BA.5. Of note, BA.2.75 caused focal viral pneumonia in hamsters, characterized by patchy inflammation interspersed in alveolar regions, which was not observed in BA.5-infected hamsters. Moreover, in competition assays, BA.2.75 replicated better than BA.5 in the lungs of hamsters. These results suggest that BA.2.75 can cause more severe respiratory disease than BA.5 and BA.2 and should be closely monitored.

Immunity to SARS-CoV-2 in COVID-19 cases has diversified due to complex combinations of exposure to vaccination and infection. Elucidating the drivers for upgrading neutralizing activity to SARS-CoV-2 in COVID-19 cases with pre-existing immunity will aid in understanding immunity to SARS-CoV-2 and improving COVID-19 booster vaccines with enhanced cross-protection against antigenically distinct variants. This study revealed that the magnitude and breadth of neutralization responses to SARS-CoV-2 infection in breakthrough infections are determined by upper respiratory viral load and vaccination-infection time interval, but not by the lineage of infecting viruses. Notably, the time interval, but not the viral load, may play a critical role in expanding the breadth of neutralization to SARS-CoV-2. This illustrates the importance of dosing interval optimization in addition to antigen design in the development of variant-proof booster vaccines.One-Sentence SummaryViral load and infection timing define the magnitude and breadth of SARS-CoV-2 neutralization after breakthrough infection.