The study is one of the most in-depth examinations of how the virus multiplies in human cells.

According to new research by the National Institutes of Health, the virus causing Covid-19 can spread to the brain and heart within days of initial infection and stay alive for months in the organs.

The research authors revealed that the virus may spread to practically every organ system in the body, which could contribute to the persistent symptoms reported in "long COVID" patients.

The work is regarded as one of the most in-depth examinations of how the virus multiplies in human cells and remains in the human body.

Ziyad Al-Aly, an MD who has researched the long-term effects of Covid on the body, said the research is "remarkably important" because it sheds some light on "why long COVID can occur even in people who had a mild or asymptomatic acute disease.”

Researchers studied tissue samples from 44 autopsies from cases that resulted in death after contracting Covid during the first year of the epidemic. Viral particles remained present for up to 230 days after the first appearance of symptoms in numerous organs, including the heart and brain. According to the researchers, this might be an infection with faulty viral particles, which has also been observed in measles patients with prolonged infections.

Raina MacIntyre, a professor of global biosecurity at the University of New South Wales, said the chronic illness outcomes in the future are unknown. She adds, "These are unanswered questions which call for a precautionary public health approach to mitigation of the spread of this virus.”

Unlike previous COVID-19 autopsy studies, the NIH team had a more thorough post-mortem tissue collecting method, which often happened within a day of the patient's death. The researchers also utilized a number of methods to preserve tissue in order to determine virus levels. They were able to propagate the virus from a variety of tissues, including numerous tissues like the heart, lungs, small intestine, and adrenal glands.

The authors concluded that “our results collectively show that while the highest-burden of SARS-CoV-2 is in the airways and lung, the virus can disseminate early during infection and infect cells throughout the entire body, including widely throughout the brain,”