Coronavirus patients who remain positive weeks after diagnosis may harbour dead virus particles that can’t be distinguished from infectious ones in tests, scientists in South Korea found.
The virus dies one to two weeks after infecting and proliferating inside respiratory cells, doctors at the National Medical Center in Seoul said.
Pieces of the virus’s RNA may remain in cells and be detected by a nucleic acid test a month or two after infection, underscoring the limitation of Covid-19 testing, they said.
Some Covid-19 patients have continued to test positive over more than a month, said Peter Collignon, a professor of clinical medicine at the Australian National University Medical School in Canberra.
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It’s possible that the virus detected in these patients isn’t viable or capable of causing an infection, “but we need better animal models to see if it’s dead or alive,” he said.
How long an individual excretes infectious virus in their respiratory secretions and faecal matter is key to determining the optimal time an infected person should self-isolate or be quarantined. Previous studies indicate that very ill patients remain infectious longer than people who experience a mild illness.