New Delhi: A new study by scientists at the National Institutes of Health (NIH) in the US has found that SARS-CoV-2 causes systemic infection and can persist in the body for months. Systemic infection affects the whole body, rather than a single organ or body part.
The results of the study, yet to be peer-reviewed, were recently released online in a manuscript under review for publication in the journal, nature, The study was done at the NIH in Bethesda, Maryland.
Acute COVID-19 infection causes multi-organ dysfunction. When patients experience symptoms for a long time, it is called a post-acute sequelae of SARS-CoV-2 (PASC) or tall covid,
Not much information is available about the burden of infection outside the respiratory tract, and how much time the body needs for viral clearance. To find answers to these questions, NIH scientists conducted this study.
SARS-CoV-2 can spread during initial infection and infect cells throughout the body
Although the burden of SARS-CoV-2 is highest in the airways and lungs, the virus can spread early during infection and infect cells throughout the body, including widely throughout the brain, US scientists found. . The virus is able to replicate outside the respiratory tract, and can spread to the cardiovascular organs, lymphoid tissues, gastrointestinal tract, kidney and endocrine glands, and reproductive tissues.
The authors call the study the most comprehensive analysis of SARS-CoV-2 cellular tropism (host tissues that support growth of a particular pathogen), quantification, and persistence throughout the body and brain.
The study said that the delay in viral clearance could be one of the reasons behind the persistent symptoms in long-term covid sufferers.
The authors noted in the study that understanding the mechanisms by which SARS-CoV-2 persists, and the cellular host response to viral persistence, holds promise for improving the clinical management of chronic COVID-19.
US scientists conducted extensive autopsies on a diverse population of 44 individuals who died from or with COVID-19 up to 230 days after initial symptom onset. The autopsy was performed to map and measure SARS-CoV-2 distribution, replication and cell-type specificity in the human body, including the brain, the study said. Autopsies were done only of fatal cases and not those with prolonged covid.
The study found that the SARS-CoV-2 virus is widely distributed even among patients who died with mild to asymptomatic COVID-19.
Furthermore, the virus replicates in many pulmonary and extra-pulmonary tissues in the early stages of infection.
The scientists consistently detected SARS-CoV-2 RNA at multiple sites, including regions of the whole brain, for up to 230 days after the onset of symptoms.
SARS-CoV-2 was found in all 44 cases, and in 79 of 85 anatomical locations, and body fluid samples were taken. Scientists detected the highest burden of SARS-CoV-2 RNA in the respiratory tract of early cases.
Despite the wide distribution of SARS-CoV-2 in the body, there were very few instances of inflammation or direct cytopathology (structural changes in host cells due to viral invasion) outside the lungs.
The authors postulated that the persistence of viral RNA and single guide RNA (sgRNA) may represent defective virus infection, which has been described in persistent infection with measles virus.
early viremic phase
The authors note that their findings support an early viremic phase, which seeds the virus throughout the body after pulmonary infection. The viremic phase is associated with viremia, and the spread of the virus into the blood from the initial site of infection.
One of the patients was a teenager with no evidence of multisystem inflammatory syndrome, suggesting that even infected children without severe COVID-19 may experience systemic infection with SARS-CoV-2.
A less robust innate and adaptive immune response outside the respiratory tract may account for less efficient viral clearance in extrapulmonary tissues.
SARS-CoV-2 was found in the brains of all six late cases, and in the brains of five patients at most sites evaluated, including one patient who died 230 days after infection, the study said. had died.
Of the 44 patients, SARS-CoV-2 RNA was found in 43 patients’ respiratory tissues, 35’s heart tissue, 38’s lymphoid tissue, 32’s gastrointestinal tissue, 28’s renal and endocrine tissue, 30’s reproductive tissue found. and brain tissue 10, the study found.
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