In the United States, the 1918 influenza killed 675,000 people. In 19, an influenza pandemic killed at least twenty million, and perhaps as many as fifty million, people worldwide. Some of the pandemics were extraordinarily destructive. Influenza pandemics do not happen very often, but they cause such dramatic outbreaks that it is possible to look back at the historical record and see evidence of them going back hundreds of years. Such hybrids are able to spread explosively, often breaking out over entire continents nearly simultaneously - these global outbreaks are called pandemics. Sometimes a hybrid virus can be formed that has acquired surface proteins that are completely unfamiliar to everyone’s immune system. If two different influenza strains infect the same host cell, the genome segments can get shuffled and packaged in new combinations. Remember, the influenza genome is comprised of eight individual genetic segments each of which must be replicated and then packaged into a protein shell during the intracellular replication cycle. ” “Shift” is made possible because of a process called reassortment (Figure 5). Instead of accumulating mutations that gradually change the appearance of its surface proteins, it can acquire entirely new surface proteins. The most important implication of seeing Omicron becoming a new SARS-CoV-2 pandemic, due to its numerous functional mutations that confer antigenic shift, is the essential need for new SARS-CoV-2 Omicron-specific vaccines.The influenza virus has another even more dramatic strategy to evade the immune system. With Omicron comes the first “antigenic shift” and a new pandemic virus. To carry the approximate analogy with influenza further, the immunodominant spike (S) protein of SARS-CoV-2 is like the immunodominant hemagglutinin (H) protein of influenza A.īefore Omicron, variants of SARS-CoV-2/COVID-19 were analogous to “antigenic drift,” e.g., D614G and the four previous WHO-designated variants of concern: Alpha, Beta, Gamma and Delta. In addition, Omicron as a “COVID-21” pandemic means we should reconsider the future of SARS-CoV-2 in terms of what to anticipate and how to recognize what actions to take. In my opinion, this concept that the SARS-CoV-2 Omicron variant of concern is already becoming the second SARS-CoV-2 pandemic, a “COVID-21,” is crucial because it means we will need to reexamine our responses to Omicron. Influenza A virus antigenic shifts require new pandemic influenza-specific vaccines. Mutations in the immunodominant hemagglutinin (H) protein of influenza cause major antigenic changes termed “antigenic shift” (rather than lesser, more frequent changes termed “antigenic drift”). With influenza, an antigenic shift is a hallmark of a new influenza pandemic. Of note, these authors do not propose that Omicron will become a second pandemic, despite their use of the term “Omicron antigenic shift.” While influenza antigenic shift is defined as genetic reassortment of the RNA genome segments, the mechanism of accumulation of a large number of mutations in SARS-CoV-2 Omicron S remains to be established.” “The staggering number of substitutions present in Omicron S marks a dramatic shift in antigenicity and is associated with immune evasion of unprecedented magnitude for SARS-CoV-2 and a putative broadening of tropism. 14, an international group of renowned researchers posted a manuscript on bioRxiv titled, “Broadly neutralizing antibodies overcome Omicron antigenic shift.” They state: Lucey, MD, MPH, FIDSA Facebook Twitter LinkedIn Email Medical Education Community of Practiceĭaniel R.Fellows-In-Training Career & Education Center.myIDSA Practice Managers Community Opt-in Form.Antimicrobial Stewardship Centers of Excellence Program.
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