The coronavirus that causes Covid-19 can spread from the respiratory tract to the heart, brain and almost every organ system in the body within days, where it can persist for months, a study finds.
In what they describe as the most comprehensive analysis to date of the spread and persistence of the SARS-CoV-2 virus in the body and brain, scientists at the US National Institutes of Health said they found that the pathogen is capable of is to replicate far beyond human cells. the airways.
The results, released online Saturday in a manuscript under review for publication in the journal Nature, point to delayed viral clearance as a possible contributor to the lingering symptoms that so-called long Covid patients cause. Understanding the mechanisms by which the virus persists, along with the body’s response to each viral reservoir, promises to help improve care for those affected, the authors said.
“This is remarkably important work,” said Ziyad Al-Aly, director of the Clinical Epidemiology Center at the Veterans Affairs St. Louis Health Care System in Missouri, which has led separate studies on the long-term effects of Covid-19. “For a long time we have been scratching our heads and wondering why Covid seems to affect so many organ systems. This article sheds some light and may help explain why Covid can occur for a long time, even in people with mild or asymptomatic acute illness.”
The findings and techniques have not yet been reviewed by independent scientists, and mostly relate to data collected on fatal Covid cases, not patients with long-term Covid or “post-acute consequences of SARS-CoV-2,” such as the is also mentioned.
Controversial Findings
The propensity of the coronavirus to infect cells outside the respiratory tract and lungs is disputed, with numerous studies providing evidence for and against the possibility.
The research conducted by the NIH in Bethesda, Maryland, is based on extensive sampling and analysis of tissues taken during autopsies on 44 patients who died after contracting the coronavirus during the first year of the U.S. pandemic
The burden of infection outside the respiratory tract and the time it takes to clear the virus from infected tissues are not well characterized, especially in the brain, wrote Daniel Chertow, who leads the NIH’s Emerging Pathogens Section, and his colleagues.
The group detected persistent SARS-CoV-2 RNA in multiple parts of the body, including regions in the brain, for up to 230 days after symptoms began. This could be infection with faulty virus particles, which has been described in persistent infection with the measles virus, they said.
“We don’t fully understand Covid for a long time, but these changes could explain the ongoing symptoms,” said Raina MacIntyre, a professor of global biosafety at the University of New South Wales in Sydney. MacIntyre was not involved in the study, which she said “provides a warning about a massive infection in children and adults.”
Precautionary approach:
“We don’t yet know what burden of chronic disease will result in the coming years,” she said. “Will we see early onset heart failure in survivors, or early onset dementia? These are unanswered questions that call for a preventive public health approach to reduce the spread of this virus.”
Unlike other Covid autopsy studies, the NIH team’s postmortem tissue collection was more extensive and typically occurred within about a day of the patient’s death.
The researchers also used a variety of tissue preservation techniques to detect and quantify viral levels, as well as grow the virus collected from multiple tissues, including the lung, heart, small intestine and adrenal gland of deceased Covid patients during their first week of illness.
“Our results collectively show that while the greatest burden of SARS-CoV-2 is in the respiratory tract and lungs, the virus can spread early during infection and infect cells throughout the body, including widely in the brain,” the authors said.
The study provides pathological data that supports findings from previous research, for example that SARS-CoV-2 directly kills heart muscle cells and that those who survive an infection have cognitive impairment, said MacIntyre of the University of New South Wales.
‘Viremic’ phase
The NIH researchers state that infection of the pulmonary system can result in an early “viremic” phase, in which the virus is present in the bloodstream and spread throughout the body, including across the blood-brain barrier, even in patients with mild or no symptoms. One patient in the autopsy study was a young person who likely died of unrelated complications from an attack, suggesting that infected children without severe Covid-19 may also experience systemic infection, they said.
The less efficient viral clearance in tissues outside the pulmonary system may be related to a weak immune response outside the airways, the authors said.
SARS-CoV-2 RNA was detected in the brains of all six autopsy patients who died more than one month after developing symptoms, and in most of the sites evaluated in five of the brains, including one patient who died 230 days after onset. of the symptoms died.
The focus on multiple brain regions is particularly helpful, said Al-Aly of the Veterans Affairs St. Louis Health Care System.
“It may help us understand the neurocognitive decline or ‘brain fog’ and other neuropsychiatric manifestations of long-term Covid,” he said. “We need to start thinking of SARS-CoV-2 as a systemic virus that can disappear in some people, but persist for weeks or months in others and cause long-term Covid – a multifaceted systemic disease.”
(This story was not edited by DailyExpertNews staff and was generated automatically from a syndicated feed.)