A new study has found coronavirus patients who recover from the disease may still carry remnants of it deep in their lungs.
The study published in Cell Research could indicate why some patients test positive for the virus after recovering from it.
Dr Bian Xiuwu of the Army Medical University in Chongqing, southwest China – who led the research team – said the work "provided the first pathological evidence for residual virus in the lung for a patient [who tested negative] three consecutive times," according to a report in the South China Morning Post.
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The findings were based on a post-mortem examination of a 78-year-old woman who had coronavirus and received antiviral treatment. She recovered and returned negative results in three rounds of testing based on nose and throat samples.
However one day later she suffered a cardiac arrest and died. The subsequent post-mortem found no trace of the virus in her major organises like heart, liver and skin, but strains of the virus were found deep in her lungs.
The news comes as medical experts investigate why some patients who have recovered from the virus returned positive tests, including 160 people in South Korean. Similar cases have been reported across Asia including in Hong Kong, Taiwan, Vietnam and the Philippines. Some were more than two months after the initial test.
The role of immunity and antibodies is of key interest to leaders and health experts amid the pandemic and could be the key to unlocking societies and travel.
However the WHO has warned there is no evidence having the virus once means one cannot get it again.
Experts believe social distancing and some measures to stop the spread of the disease will need to remain in place until a vaccine is found – assuming this can be done.
Bian and his colleagues said the case shows there is an "urgent need to understand the pathogenesis of Sars-CoV-2 infection".