September 4, 2020

expert reaction to preprint systematic review of studies looking at viral cultures for COVID-19 infectivity assessment

A preprint, an unpublished non peer-reviewed study posted on medRxiv, has reviewed studies looking at viral cultures for COVID-19 infectivity assessment.

Prof Ben Neuman, Chair of Biological Sciences at Texas A&M University-Texarkana, and Visiting Associate Professor at the University of Reading, said: 

“This review runs the risk of falsely correlating the difficulty of culturing SARS-CoV-2 from a patient sample with likelihood that it will spread. 

“Virus culturing is actually growing the virus from the swab instead of cracking it open and reading out the RNA inside, which is what is currently done in swab testing. 

“Odd as it may seem, culturing a virus from a patient sample is not trivial, and depends on a number of factors other than the potential infectivity of the virus.  Firstly, the efficiency with which a virus is recovered depends on the cells you use, and the commonly used Vero cells are an expedient but rather inefficient choice.  Vero cells are inexpensive and relatively easy to handle, but only produce modest amounts of virus compared to a human lung. 

“Secondly, virus particles from a clinical sample come mixed in an immunological soup of factors released by sick cells, whereas the smallest respiratory droplets produced by talking or breathing may contain little more than the virus itself.  It is natural that this mix would change as the disease progresses, making it more difficult to culture virus later in infection, but would not necessarily change the way the virus spreads. 

“Without a good way to fix the inherent problems in culturing SARS-CoV-2, we should not recommend virus culture for routine screening or as a basis for policy decisions.” 

Preprint: ‘Viral cultures for COVID-19 infectivity assessment. Systematic review’ by Tom Jefferson et al.  This work is not peer-reviewed. 

https://www.medrxiv.org/content/10.1101/2020.08.04.20167932v3 

All our previous output on this subject can be seen at this weblink: 

www.sciencemediacentre.org/tag/covid-19 

Declared interests 

None received.