under the microscope
By Rodney E . Rohde , PhD , MS , SM ( ASCP ) CM SVCM , MBCM , FACSc
What Does a SARS-CoV-2 Variant Mean ?
Just when we were all starting to breathe a ( small ) sigh of relief with the news of successful therapies ( antivirals , steroids , and monoclonal antibodies ) and multiple vaccines for the SARS-CoV-2 virus to help with prevention of a COVID19 infection , we started seeing new headlines about a new virus variant ( strain ) emerging in the United Kingdom ( UK ). Scientists and public health officials began reporting what appeared to be a COVID19 surge in December caused by a SARS-CoV-2 variant . While it is likely too early to know , this new strain appears to be transmitting faster than earlier strains .
The UK sequences 5 percent to 10 percent of all COVID-19 cases for epidemiological surveillance . In 117 of 255 sequenced cases , roughly 50 percent of them were detected to be in a unique phylogenetic cluster . In common language a distinct cluster of viruses just means that they are very similar to each other ( genetically ) versus to other strains of the virus . The “ new ” detected viruses were initially designated as Variant Under Investigation ( VUI ) – 202012 / 01 upon detection , but on further review given its rapid spread has been re-designated as Variant of Concern ( VOC-202012 / 01 ) or B . 1.1.7 ( a name derived from its phylogenetic heritage ). It is important to understand that the terms “ variant ,” “ strain ,” and “ lineage ” are synonyms . Currently , the general media and scientists are using them in addition , for their reporting .
Global reports by Public Health England have illustrated that the B . 1.1.7 strain has quickly spread outside of England and the UK . At the time of writing this column ,
To View Global reports by Public Health England
almost 50 countries have detected this new variant , including the United States . While the world still awaits the analysis of a stronger ( more cases ) data set for more certainty , early statistical modeling by the Centre for Mathematical Modelling of Infectious Diseases at the London School of Hygiene and Tropical Medicine implies the transmission of this variant may be 56 percent greater . The data also exhibits a higher Rt ( reproductive rate is the number of secondary infections that occur from a single infection ) of 0.7 versus 0.4 from early strains .
Is it normal for viruses to change ?
Viruses , especially RNA viruses , change rapidly ( mutate ). All viruses do this over time and the coronaviridae ( SARS-CoV-2 belongs ) is no different . Mutations occur in the sequence of nucleic acids by base changes . Sometimes these mutation events during virus evolution will be “ silent ” which means the changes do not produce anything of concern to its host ( in this case , humans ).
On the other hand , sometimes the mutation is not silent and can result in the virus producing new or changed proteins or
features that produce changes resulting in a new or related phenotype . Scientists refer to minor changes in a microbial phenotype as resulting in an antigenic drift , while major changes are known as an antigenic shift . A drift is usually less problematic , for example , because the human immune system will likely still recognize the microbe and mount a response .
Many people may understand this situation with the ongoing changes of influenza viruses , which means each year we receive ( usually ) a new cocktail of vaccine for protection due to flu virus mutations . Fortunately , coronaviruses mutate slower than other RNA viruses . The scientific community has already documented SARS-CoV-2 variants that differ from the original Wuhan strain and involved the well know spike protein that is critical for virus cell-mediated entry .
What are some of the major concerns about this variant ?
While there are always concerns with virus mutation , I believe there are primary issues the scientific , public health and
• At the time of writing this column , almost
50 countries have detected this new variant , including the United States .
• While the world still awaits the analysis of a stronger ( more cases ) data set for more certainty , early statistical modeling by the Centre for Mathematical Modelling of Infectious Diseases at the London School of Hygiene and Tropical Medicine implies the transmission of this variant may be
56 % greater .