Viruses are tiny, non-cellular infectious agents. They are approximately one one-hundredth the size of an average bacterium and cannot be seen with an optical microscope. They are often round and have projections on their outside coat, called spike proteins, and contain strands of RNA or DNA. The spike proteins act like an anchor, allowing the virus to attach itself to a cell. Once attached to a cell, the virus hijacks the cell, forcing it to make replications of the virus. Sometimes, during this replication phase, a mutation may occur. The new, mutated virus is called a variant. Some mutations allow the virus to be more easily spread, while other mutations make the virus more resistant to treatment or vaccines.
The CDC classifies a variant of concern as a variant with one or more mutations that allow the virus to either be more contagious, less responsive to treatment, or more resistant to vaccines. A variant of high consequence is one for which there is clear evidence that “prevention measures or medical countermeasures have significantly reduced effectiveness relative to previously circulating variants.” Currently, the SARS-CoV-2 virus, aka COVID-19, has five known variants of concern and no known variants of high consequence.
The Alpha variant was the first major variant of concern. Identified in the United Kingdom in the fall of 2020, it spreads approximately 50% better than the original SARS-CoV-2. There is some evidence that the Alpha variant may cause more severe disease, but vaccines and monoclonal antibody therapies appear to be effective against it.
The variants Beta, first identified in South Africa, and Gamma, first identified in Brazil, both exhibit increased transmissibility and appear more resistant to antibody therapies. There is also evidence that vaccines are slightly less effective against them. Delta, currently the most prevalent variant in the U.S., has larger spike proteins causing it to be almost twice as contagious as the original virus. It does appear, at least at present, that Delta may cause slightly less severe disease and may not be neutralized as well by antibodies in vaccinated people.
Early data shows a slight decrease in vaccine effectiveness against Delta, however, due to its increased transmissibility, unvaccinated people are at high risk for Delta infection. In fact, at present, 99% of hospitalizations and deaths from COVID-19 in the US are in unvaccinated people due to the Delta variant. Lastly, there have been some early reports of a Mu variant, but little is known about it yet.
A word about masks. Because viruses are so small, they can easily pass through most cloth masks, plus masks are rarely tight fitting and have gaps on the top and sides. Paper masks have smaller pores and are more effective against viruses, but they too are not airtight. Masks may impart a false sense of security. The key to protection against this virus is vaccination. Vaccination is highly effective at preventing severe disease, hospitalization, and death, but vaccinated people can still test positive for the virus, but they are much less likely to become ill from it. Once everyone is vaccinated, we can return to some semblance of normalcy, assuming, of course, that we can remember what normal was like.
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By Peter Galvin, MDBLOG COMMENTS POWERED BY DISQUS