Francisco R. Velázquez, M.D.: What we need to know about the Delta variant

By Francisco R. Velázquez, M.D., S.M., FCAP Spokane Regional Health District

This summer is shaping up to be vastly different than a year ago. We have seen unprecedented heat, lots of smoke from wildfires and a new alphabet of COVID-19 variants. By now, we are almost 18 months into this pandemic, and although we would like to get beyond it, the reality is that the virus is still here. Which brings us to the conversation about variants, specifically the delta variant.

The earliest documented COVID-19 infection caused by the delta variant (B.1.617.2) goes back to October , in the Indian state of Maharashtra. It spread through India, then Great Britain, and on to many other countries where it has been associated with a significant increase in cases. It is now present in 132 countries including the Unites States. In many of these countries, this variant accounts for over 80% of all sequenced viral specimens collected. Some of these are: Great Britain, Australia, China, Denmark, Israel, Russia, South Africa, and now the U.S.

The first sequence from a case identified in the U.S. dates back to March 16. The variant has been identified in all 50 states, and according to the Centers for Disease Control and Prevention, accounts for over 80% of all sequenced cases. It is also estimated to account for every one out of four documented cases in the U.S. In Washington, January 2020 through Aug. 3, we identified 2,123 cases total, with the caveat that only 17-18% of all confirmed positive cases are typically sequenced. This represents over 85% of all variants identified in contrast to approximately 12% in early June. Spokane County, for the same period, has 49 cases, roughly 11% of the total variant cases identified through sequencing. What all these numbers tell us is that this variant spreads quickly, particularly in areas with lower vaccination rates.

Why is this variant somewhat different than the others? Multiple factors contribute to the relative uniqueness of this variant.

First, we know it is more transmissible than the original strain. The alpha variant (B.1.1.7) is over 50% more transmissible than the original strain, and delta is 50-65% more transmissible than alpha. Some data suggests it is up to 225% more effective at transmission.

Second, the viral load, or the amount of virus present in infected individuals, is much higher than any other variant. It has been quoted to be up to 1,000 times higher. That translates into a higher transmission rate per infected individual. Originally, it was reported that each infected person could potentially infect between two to 2½ people. In contrast, the delta variant has been reported to cause between three and four infections per person. Or about twice as many people can get infected by one person.

Third, the CDC recently reported that even though the vaccines protect us from hospitalization and death, those of us vaccinated are more likely to transmit the delta variant to others who are not vaccinated because of its high viral load compared to the original virus.

If you do the math, it explains the significant speed of community transmission.

In addition, early studies from England and Scotland suggest that the rate of possible hospitalization for delta-infected individuals was up to 2½ times higher. Although this may not be the case everywhere, it is worth noting. Recent data from England, where analysis was done of samples obtained during the recent surge in late May and early June , identified rapid growth of infections. This coincides with the increase in delta variants.

Key findings of this study pointed to a fivefold increase in seroprevalence in younger children (5-12 years of age) as well as in young adults (18-24 years of age) as compared to those over 65. A less pronounced (2.5-fold higher rate) but still significant increase was seen in those under 50 as compared to those over 50 years of age. These findings seem to agree with the increase of infections at a global level in younger populations.

This is also true in our state as well as in Spokane County where cases in the age group of 10-29 has been over 30% for the past few weeks. If we add in the case numbers for ages 30-39, these age groups combined are around 50% of the cases on an average day.

The good news, despite this increase in cases and variants, is that the available vaccines do work, and that includes protection against the variants. Although protection from infection is not 100%, and mild symptoms in the case of a delta variant breakthrough could be experienced, protection from more symptomatic, severe disease is still very high.

Combine vaccination with the other tools we have to combat the virus – face masks, hand-washing, sanitizing, testing and respiratory etiquette – and we will overcome the pandemic and return to a normal life. If you are not immunized, please follow the simple precautions presented at SRHD.org.

If you can, and are so inclined to get the vaccine, it is the best option for your protection and the protection of others.

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