COVID: Autopsies show virus spreads widely in the body

Autopsy results from 44 people who died of COVID-19 show how the virus spreads not only to the respiratory system but throughout the body, including the brain, continuing for months in some patients.

A description of the results, published in the peer-reviewed journal Nature in December, highlights how widespread the burden of infection can be, with viral fragments found in 79 of 85 body locations in 44 patients.

The small study forms “the most comprehensive analysis to date of the cellular tropism, quantity and persistence of SARS-CoV-2 throughout the human body, including the brain,” according to its authors.

“Our results show that although the highest burden of SARS-CoV-2 is in respiratory tissues, the virus can spread throughout the body.”

The virus was able to spread to multiple organs and systems even in patients who died within a week of feeling their first symptoms, the researchers found.

The 44 people whose autopsies contributed to this research were all unvaccinated individuals who had died of COVID-19. The average age of individuals was 62.5 years and 61.4 percent had three or more comorbidities. The median time between symptom onset and hospitalization was six days, with 18.5 days being the median interval between symptom onset and death.

Across the board, the autopsies showed that the virus was able to penetrate multiple body systems, although the researchers noted that there was a significantly higher load of SARS-CoV-2 RNA found in respiratory tissue. The researchers found that the virus had invaded more than 35 types of cells and membranes across different systems in the body.

Of the 44 autopsies, 11 were whole-body and brain autopsies, providing the most complete picture of viral spread in those individuals.

Of these 11, the two with the shortest duration between the onset of symptoms and death – four days and five days – had the highest amounts of viral RNA levels in their respiratory system, with high levels also found in the entire cardiovascular system and optic tissue, among others. .

SARS-CoV-2 was found in at least one site in central nervous system or brain tissue in 10 of 11 of these autopsies, including five of six of those who died more than a month after the first onset of symptoms.

The researchers noted that although significant viral traces were found, the actual structural brain tissue was largely unaffected by the virus.

The individual who had the longest duration between symptom onset and death — 230 days — had been hospitalized multiple times and ultimately died of lung transplant complications, not COVID-19, but was found to be positive for COVID-19 and there were traces of the virus in many parts of their bodies, including their respiratory system, heart, eye tissue and brain.

This shows that the virus can stay in the body in some patients for months, the researchers noted.

The cause of death varied between individuals. Thirty-eight died of COVID-19, while six died of another underlying problem while having COVID-19. Of those who died from the virus, 35 had either acute pneumonia or severe lung damage at the time of death.

Two of the patients involved had only mild symptoms of COVID-19 and had died of other causes, but were still found to have SARS-CoV-2 RNA widely spread throughout their bodies, suggesting that although most most of the autopsies were focused on severe and fatal cases, the virus can penetrate the body a lot even in mild cases.

The study is limited by its small scope and its focus on unvaccinated, older individuals who died of COVID-19, meaning these results may not reflect what happens when younger, vaccinated individuals contract the virus.

Previous autopsy research has found evidence of COVID-19 across multiple systems, but some have theorized that viral traces found outside the respiratory system may have been due to blood remaining in the tissues or cross-contamination. Researchers say that’s not the case in this new study, which confirmed SARS-CoV-2 at the cellular level.

How long the virus persisted inside the tissues was another aspect the researchers were interested in. They found that among those who had a longer interval between the onset of symptoms and death, the difference between the level of virus in respiratory and non-respiratory tissues was significantly reduced. This may be because different tissues are better at fighting the virus and identifying it, the researchers theorized.

“Understanding the mechanisms by which SARS-CoV-2 evades immune detection is essential to guide future therapeutic approaches to facilitate viral clearance,” the authors said.