Francisco R. Velázquez: Why omicron BA.2 is significant and why you should care

Over the past two and a half years, we have learned a lot about COVID-19, probably more than any other virus in the recent past. The global impact has been unprecedented in many areas – health care, mental health and the economy to name a few.

So, the question is why has this virus been different than others? That’s a complicated question with a simpler answer: We have experienced a global spread of a virus that has continuously adapted with thousands of mutations, as frequent as perhaps every 11 days. Luckily most of the resulting variants have not had a significant presence. A few have, in aggregate all resulting in over 470 million confirmed cases and over 6 million deaths across the globe. The latest variant was initially reported on Nov. 24, subsequently labeled as a variant of concern and assigned the 15th letter of the Greek alphabet, omicron.

Since then, omicron has been responsible for more than 90 million infections in just 10 weeks. That is more COVID-19 cases than those recorded in all of 2020. This variant has more mutations than others, which are partly responsible for its contagiousness. There are five subvariants in its lineage: BA.1, BA.2, BA.3, BA.4 and BA.5. Now there are multiple sublineages, including BA.2.12 and BA.2.12.1, responsible for the increase in cases in New York and other areas. Each one of these was identified in a different part of the world and carried additional and different mutations. BA.2 is the most common worldwide.

Why is BA.2 and its sublineages receiving so much attention? Several reasons. First and foremost, it caused another surge in cases in several countries in Europe and Asia. And it is responsible for the increase in cases in approximately 25 states. Although technically a member of the Omicron family, over 40 mutations separate it from its closet relative BA.1. That is a significant number of mutations, as many as those that differentiated the previous variants, alpha, beta and delta, from each other. The BA.2 sublineage shares some omicron characteristics, but also has some differences. These are the reason for the enhanced vigilance around the world.

Omicron BA.2 has all the BA.1 mutations plus six additional ones with half in the spike protein region known as receptor binding protein, critical for the connection with the human cell receptors. The combination of mutations has caused structural and electrostatic differences that improve receptor binding and promote stronger bonds. The new format also helps it hide better from naturally occurring antibodies. More effective transmission and immune evasion make BA.2 about 30% more transmissible.

There are a few more differences. For example, the basic reproduction number of BA.2, which represents the number of cases directly generated by an infected person, ranges from eight to 12 according to various research studies. That means an infected person can transmit to as many as 12 people. Earlier strains had a basic reproduction number of roughly three to five. For comparison, measles, the most contagious of communicable diseases, ranges from 12-18. Recent studies also suggest that this variant can replicate faster than BA.1. Reports from Denmark, where BA.2 caused a significant surge, suggested that household transmission was twice as much with BA.2 as compared to its predecessors.

At this point BA.2 is almost 88% of all sequenced cases in the United States, according to the Centers for Disease Control and Prevention, and more than 85% of all cases globally, according to the World Health Organization (WHO). Closer to home, the Washington State Department of Health reported that BA.2 is approximately 79.7% of cases sequenced through April 2.

What does all this mean? That is the key question. Reported cases and hospitalizations statewide continue to remain steady despite the increase in BA.2. It has displaced BA.1, as happened with delta, although the replacement is not resulting in more cases and hospitalizations. We have seen this pattern in other parts of the world where the subvariant becomes dominant but there is a minimal increase in numbers. If this trend continues, we may see a modest rise in cases and hopefully very limited impact on our health care capacity.

Understanding the omicron variant helps you understand the current phase of the pandemic. Although we’re not ready to ring the alarm bell, we are being watchful, and so should you.

With accurate information about the virus, you’re able to make the best decisions to help keep you and those you care about safe. Decisions about vaccination and boosters, wearing a mask, attending large events or hosting gatherings can be made confidently when watching the virus’s latest trends and variant activity.

Public health guidance is effective at protecting you from hospitalization and severe symptoms, and helps you continue living your life to the fullest.

Francisco R. Velázquez, M.D., S.M., FCAP, is the Spokane Regional Health District health officer.