Dr. William A. Petri, an immunologist at the University of Virginia School of Medicine, answers this week’s questions from readers on COVID-19. Dr. Petri will keep dishing on COVID-19 and answering your questions each week in The Daily Progress for as long as you have questions. Send them to Editor Lynne Anderson at: email@example.com, and she will forward them to Dr. Petri.
We have had lots of COVID-19 variants; why the alarm about omicron?
Omicron appears to be responsible for the new wave of the COVID-19 pandemic in South Africa. What has everyone concerned is epidemiology from Gauteng Province in South Africa, which encompasses Johannesburg, a city of 6 million people. COVID-19 cases there have gone from 300 cases a day the first week of November to 18,000 on Nov. 23. Omicron appears responsible, as it was identified as the cause in all 77 cases of COVID-19 where the virus was sequenced from Nov 12-20. Omicron may spread more easily because it has over 30 mutations in the spike glycoprotein.
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Which countries have the omicron variant?
South Africa, Botswana, Hong Kong and Belgium have all reported the detection of omicron. So far the CDC reported on Friday that it has not yet been detected in the US.
Why are mutations in Spike important?
The spike protein is on the outside of coronaviruses and is responsible for attaching the virus to human cells and enabling the virus to fuse to human cells after attachment. The spike glycoprotein is what is the target for all of the COVID-19 vaccines and also for anti-spike antibodies that are used to treat or prevent infection. It is an evolutionary advantage to the virus to mutate the spike protein in a way that increases virus transmission, infection and evasion of immunity.
How does omicron compare to the delta variant?
As you likely know, the delta variant is entirely responsible for the current wave of the pandemic in the U.S. that began in July and continues today. Delta originated a year ago from the pandemic in India. It is much more infectious than the alpha variant (that originated in Kent England) which it outcompeted last summer. The delta variant won out over alpha because of mutations in the virus spike protein that enabled it to be better than alpha in attaching and invading human cells to cause infection. Delta also has mutations that make it harder for vaccines to work. This was the reasoning behind the recommendation last week for vaccine boosters for everyone age 18 years and older.
Omicron has many of the same mutations in the spike glycoprotein that delta has, and more to spare — a total of over 30 mutations in spike. The fact that omicron is responsible for the current pandemic wave in Johannesburg suggests that it is more easily transmitted person-to-person than delta. There have also been isolated instances of vaccine breakthrough infections and second infections that may suggest that omicron is better at evading immunity than delta.
How will we know if omicron is in Virginia?
One piece of good fortune is that one of the commonly-used PCR tests detects omicron. This will hasten identification of the variant, as it will not be necessary to sequence the virus, a much more expensive and time-consuming process for the lab.
What should I do?
Today the delta variant is our biggest threat, especially as we are in the holidays that saw last year such a huge winter wave of the pandemic. Please protect yourself and your loved ones. If you are ages five and up the most important thing is to get vaccinated against COVID-19. If you have been vaccinated (six months ago for Pfizer and Moderna and two months ago for Johnson and Johnson) get your booster. Wear masks indoors in public spaces, practice social distancing, and isolate yourself at home if you have cold or flu symptoms. Which reminds me that we are also into flu season and it is important, and not too late for everyone six months of age and older to get their annual flu shot!
What don’t we know?
Lots. We do not know if omicron is in the U.S., nor do we know for sure that omicron is more infectious than delta, or worse than delta in evading vaccines and anti-Spike monoclonal antibody therapies. The contribution of science, as well as healthcare providers on the frontlines, to combatting the biggest public health crisis of our time continues to be breathtaking. I am optimistic that we will manage this challenge just as we have delta.