According to a new study under review for the journal Nature, within days after infection, SARS-CoV-2 can spread well beyond the respiratory tract, throughout the entire body, reaching organs such as the heart or the brain, where it can survive for months. These findings could be an explanation of the phenomenon called “long Covid,” which affects many Covid-19 survivors for several months after the infection.
“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. “For a long time now, we have been scratching our heads and asking why long Covid seems to affect so many organ systems. This paper sheds some light, and may help explain why long Covid can occur even in people who had mild or asymptomatic acute disease.”
A team of researchers from the US National Institutes of Health (NIH) studied tissues taken during autopsies of 44 patients who died after being infected with SARS-CoV-2, and found evidence that the virus had spread far beyond the respiratory tract, and was present in several other organs, such as the heart or brain, even 230 days after infection.
“We show that SARS-CoV-2 is widely distributed, even among patients who died with asymptomatic to mild COVID-19, and that virus replication is present in multiple pulmonary and extrapulmonary tissues early in infection,” the study authors wrote.
According to the scientists, in an early “viremic” phase of infection, the virus may be present in the bloodstream and seeded throughout the body, including across the brain-body barrier, even in patients experiencing mild or no symptoms at all. Although the reasons for this remain unclear, the scientists believe that organs outside the respiratory tract may have less efficient innate and adaptive immune responses to the virus, and can thus provide a perfect ground for it to multiply.
Further research is needed to clarify whether these findings hold for people with long Covid who are still alive and struggle with long-term symptoms. Understanding how the virus spreads to multiple brain areas will be particularly important in order to clarify the nature of long Covid and find proper therapies.
“It can help us understand the neurocognitive decline or ‘brain fog’ and other neuropsychiatric manifestations of long Covid,” said Dr. Al-Aly. “We need to start thinking of SARS-CoV-2 as a systemic virus that may clear in some people, but in others may persist for weeks or months and produce long Covid – a multifaceted systemic disorder.”