Dead virus particles may affect test result

Coronavirus patients who remain positive weeks after examination may consider dead virus particles that can't be detected from infectious ones in tests, scientists in South Korea found.

Doctors at the National Medical Center in Seoul said, "the virus dies one to two weeks after infecting and reproducing inside respiratory cells."

Pieces of the virus's RNA may remain in cells and be detected by a nucleic acid test a month or two after infection, underlining the limitation of Covid-19 testing, they said.

According to Peter Collignon, a professor of clinical medicine at the Australian National University Medical School in Canberra, Some Covid-19 patients have proceeded to test positive over more than a month.

It's possible that the virus detected in these patients isn't viable or able of causing an infection, "but we need better animal models to see if it's dead or alive," he added.

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 mild illness.