The rate of nCoV replication in lung tissue

HONG KONG - The researchers found that the nCoV multiplied 100 times within 48 hours in lung tissue taken from Covid-19 patients.

The discovery by microbiologist Yuen Kwok-yung at the University of Hong Kong (HKU) is the first study based on tests done on lung tissue taken from Covid-19 patients. The results reveal the virulence of the virus as well as the difficulty of health authorities in the world in detecting people infected with Covid-19 compared with severe acute respiratory distress syndrome (SARS). Authorities took 6 months to control the SARS epidemic, but the challenge from Covid-19 was much greater when more than 1.7 million people worldwide had been infected since April 12. According to Yuen, countries were almost unable to control the virus before July.

nCoV multiplies much faster than SARS virus. Photo: Flipboard.

In a study published in the journal Clinical Infectious Diseases, by infecting two viruses into the lung tissue donated by six patients, Yuen and colleagues found that nCoV produces 3.2 times more viral particles than SARS in within 48 hours. "In some cases, the nCoV can multiply 100 times in 2 days while the SARS virus peaks at about 10 to 20 times the multiplication," said Dr. Chu Hin, assistant professor at HKU's School of Medicine, Research team members, said.

Although more reproductive, nCoV stimulates a slower immune and inflammatory response. Unlike SARS, nCoV almost does not stimulate the secretion of interferon, the natural protein produced by the cells of the immune system to fight the virus. Of the 13 genetic markers that cause inflammation in the lungs, nCoV activates only 3 while the SARS virus can activate 11. "Ninja-like virus, replicates inside the body with low interferon levels and slow inflammatory response", progresses Jasper Chan Fok-woo, assistant clinical professor at the Medical School, commented.

It is difficult for governments in countries to control Covid-19 because infected people do not show symptoms or only have mild symptoms. With 90% of the population not yet immune, Yuen warned the virus could continue to spread even at the end of the summer.