Over the course of the COVID-19 pandemic, we have covered the issue of variants, virus mutations that affect the way SARS-CoV-2 moves around the globe and causes disease. One particular mutation, the delta variant, has been named a "variant of concern" by the CDC, and now accounts for upwards of 83% of new COVID-19 cases in the United States. In today's post, we'll cover 5 topics about the delta variant, providing you with some new and interesting facts about the variant that is in all the headlines.
#1 What is a virus variant?
Genetic mutations are common with viruses. Each time they copy themselves in the host body, they make slight genetic mistakes and can be passed on to future generations of viruses. This is why we need a new flu shot every year - the genetic shifts are enough that we can't use last year's flu shot. When enough mutations accumulate in a virus, the result is a variant. If this variant continues to mutate with enough changes that give the virus new capabilities, then you have a strain. For example, there are three types of influenza that affect humans, A, B and C. Each type has multiple strains, which are predicted each year and are the reason for needing a new shot each year. So strains are not necessarily a scary concept, just a different shape which must be accounted for when it comes to diagnosis, vaccination, and sometimes, treatment.
#2 What is the Delta variant?
The delta variant is a group of mutations of the SARS-CoV-2 virus that originated in India and South Africa at around the end of April 2021. Since the beginning of the pandemic, Alpha, Beta, Gamma variants, all the way up to Iota, have been identified so far. As genomic surveillance reveals more variants, they will continue to be named using the Greek alphabet.
#3 What is a variant of concern?
The CDC monitors genetic drift and shift of any pathogen involved in an outbreak using genomic sequencing. Depending on the impact of those mutations on human health, they are assigned into one of three categories, from lowest concern to highest concern. Variants are examined for changes in receptor binding (how well they adhere to human cells), how well they are neutralized by antibodies (vaccine antibodies in particular), how well they respond to current treatments, and whether they continue to be recognized by current diagnostic tests. Additionally, variants are investigated for their impact on disease severity, since some variants make us sicker or lead to easier transmission between individuals. Those variants with minor impact in all or most of these areas are assigned the category "variant of interest." Those, like the Delta variant, with more significant impact in all or most of these areas, are considered "variants of concern." Those variants that have significant impact on treatment, disease severity, diagnostics, and transmission are considered "variants of high consequence." There are no SARS-CoV-2 variants of high consequence yet.
#4 How do we know that the Delta variant is spreading quickly in the United States?
While only 10% of positive COVID-10 cases are currently being sequenced nationwide (many believe we should be sequencing more), statistical analysis gives us a good estimate that around 83% of new cases are the delta variant. Why don't we sequence all the positive cases so that we can know for sure? It turns out we don't have a national program to sequence viruses during a pandemic. While we have the Advanced Molecular Detection program helping the many different labs coordinate sequencing, it really is up to the states and often, the laboratories conducting the tests to sequence or not. The vast majority of COVID tests are processed at commercial labs, which do not sequence. Sequencing is costly, and private insurance won't pay for it because knowing the variant does not impact individual patient treatment. The Pandemic Response Lab in Queens, NY is sequencing whatever samples they can procure for free, for example. The Biden administration has recently set aside $1.7 billion for increasing sequencing capacity, with $300 million being earmarked for the National Bioinformatics Infrastructure needed to handle all the shared data.
#5 How can we protect ourselves from the delta variant?
Get vaccinated! That is an essential first step. All the currently available vaccines protect us from severe illness from delta variant and all the other variants (Moderna and Pfizer provide the most protection). If positive cases in your area are soaring, and you are vaccinated, you may still want to wear a mask to prevent spreading the virus to others. Unfortunately, the recent spike in positive cases was avoidable - 99.7% of positive cases are individuals who are not vaccinated. It's a huge task, but helping convince our neighbors to get vaccinated is a significant part of protect ourselves from the delta variant and any future variants. The more individuals who are vaccinated, the slower the spread of SARS-CoV-2.
We hope this brief introduction to the delta variant has answered some questions for you. If you are curious to find out more, share your questions with us in the comments and we will do our best to ask the experts who can answer.