Nature wades through the literature on the new coronavirus — and summarizes key papers as they appear:

1 June — Positive coronavirus test is no guarantee of infectiousness

People with COVID-19 are unlikely to spread the new coronavirus if more than eight days have passed since their symptoms began, according to experiments in monkey cells.

Jared Bullard at the University of Manitoba in Winnipeg, Canada, and his colleagues seeded cultured monkey cells with 90 human samples that had tested positive for SARS-CoV-2 RNA (J. Bullard et al. Clin. Infect. Dis. http://doi.org/dw8z; 2020). The researchers found that RNA-positive samples collected more than eight days after a person’s symptoms began did not infect the cells — suggesting that people who test positive for viral RNA are not necessarily infectious.

Hospital patients who still test positive for viral RNA weeks after they began feeling ill might not need to be strictly isolated, the team says.

29 May — The nose could be the body’s entry point to infection

The nose is the probable starting point for COVID-19 infections.

Richard Boucher and Ralph Baric at the University of North Carolina at Chapel Hill and their colleagues tracked the ease with which the new coronavirus infects various cell types in the respiratory tract. The researchers found a gradient of infectivity that decreases from the upper to the lower respiratory tract: the most easily infected cells are in the nasal cavity, and the least easily infected deep in the lungs. (Y. J. Hou et al. Cell http://doi.org/dw2j; 2020). That gradient mapped neatly onto the distribution of cells that express ACE2, a protein that SARS-CoV-2 uses to enter cells.

The authors speculate that the virus gets a foothold in the nose, then sneaks down the respiratory tract when breathed into the airways. They say the results support the use of masks and preventative measures such as nasal cleansing.

Image Credit: NIAID/NIH/SPL

Thanks to Heinz V. Hoenen.  Follow him on twitter: @HeinzVHoenen