Coronavirus can persist for months by spreading through the body

The coronavirus that causes COVID-19 can spread in a few days from the airways to the heart, brain and almost every organ system in the body, where it can persist for months, according to a study.

In what they describe as the most comprehensive analysis to date of the distribution and persistence of the SARS-CoV-2 virus in the body and brain, scientists from the National Institutes of Health (NIHfrom the United States reported that they found that the pathogen is capable of replicating in human cells well beyond the respiratory tract.

The results, published online Saturday in a manuscript being reviewed for publication in the journal Nature, suggest that delayed clearance of the virus may contribute to long-term persistence of symptoms. According to the authors, understanding the mechanisms by which the virus persists, along with the body’s response to any viral reserves, promises to help improve care for those affected.

“This is extremely important work“, He said Ziyad Al-Aly, director of the center for clinical epidemiology at the Veterans Affairs St. Louis Health Care System in Missouri, who has conducted other studies on the long-term effects of COVID-19. “We have long wondered why COVID in the long term seems to affect so many organ systems. This work sheds some light and may help explain why long-term COVID can occur even in people who had a mild or asymptomatic acute illness.”.

The findings and techniques have not yet been reviewed by independent scientists, and mostly refer to data collected from fatal COVID cases, not from patients with prolonged COVID or “post-acute sequelae of SARS-CoV-2″, As it is also called.

Controversial findings

The propensity of the coronavirus to infect cells outside of the airways and lungs is controversial, with numerous studies providing evidence for and against this possibility.

Research carried out in the NIH in Bethesda, Maryland, is based on extensive sampling and analysis of tissues taken during autopsies of 44 patients who died after contracting coronavirus during the first year of the US pandemic.

The burden of infection outside the respiratory tract and the time required to clear the virus from infected tissues are not well characterized, particularly in the brain, he wrote. Daniel Chertow, who directs the emerging pathogens section of the NIH, and their colleagues.

The group found that SARS-CoV-2 RNA persisted in various parts of the body, including regions throughout the brain, for up to 230 days after symptoms appeared. This may represent an infection with defective virus particles, as has been described in persistent infection with the measles virus, they said.

“We don’t fully understand prolonged COVID, but these changes could explain the ongoing symptoms.“, He said Raina MacIntyre, Professors of Global Biosafety at the University of New South Wales in Sydney. MacIntyre was not involved in the investigation, saying that “provides a warning about indifference to massive infections in children and adults. “

Preventive approach

“We still do not know what burden of chronic diseases will occur in the coming yearsMacIntyre said. “Will we see early-onset heart failure in survivors, or early-onset dementia? These are unanswered questions that demand a preventive public health approach to mitigate the spread of this virus.”.

Unlike other investigations on autopsies of COVID, the NIH team postmortem tissue collection was more thorough and typically occurred one day after the patient’s death.

The researchers also used various tissue preservation techniques to detect and quantify viral levels, as well as to grow virus collected from multiple tissues, including lung, heart, small intestine, and adrenal gland from COVID patients who died during their first week of illness. .

“Our results collectively show that while the highest burden of SARS-CoV-2 is in the airways and lungs, the virus can spread early during infection and infect cells throughout the body, including the entire brain.”Said the authors.

The study provides pathological data to support previous research results showing, for example, that SARS-CoV-2 directly kills heart muscle cells, and that those who survive an infection suffer from cognitive deficits, said MacIntyre of the University of New south Wales.

‘Viremic’ phase

The researchers of the NIH state that infection of the pulmonary system can lead to a phase “viraemic”Early, in which the virus is present in the bloodstream and spreads throughout the body, including through the blood-brain barrier, even in patients who experience mild or no symptoms. One of the patients in the autopsy study was a young man who likely died of unrelated seizure complications, suggesting that infected children without severe COVID-19 may also experience a systemic infection, they said.

Less effective viral clearance in tissues outside the pulmonary system may be related to a weak immune response outside the respiratory tract, the authors said.

SARS-CoV-2 RNA was detected in the brains of six autopsied patients who died more than a month after developing symptoms, and in most of the assessed brain areas of five, including one patient who died. 230 days after the onset of symptoms.

Focusing on multiple areas of the brain is especially helpful, said Al-Aly of the Veterans Affairs St.

“May help us understand neurocognitive impairment or ‘brain fog’ and other neuropsychiatric manifestations of prolonged COVID“, He said. “We have to start thinking of SARS-CoV-2 as a systemic virus that can disappear in some people, but in others it can persist for weeks or months and lead to prolonged COVID, a multifaceted systemic disorder.”.