How Does the COVID Delta Variant Compare?
In late 2020, a variant of COVID-19 was detected in India that began to quickly spread.
Soon after it received the label “Delta,” it started to become the predominant strain of COVID-19 in countries of transmission. It spread faster than both the original disease and other variants, including “Alpha” that had taken hold in the UK.
Now the COVID-19 pandemic has essentially become the Delta pandemic, as the variant accounts for more than 90% of global cases.
But how does the COVID-19 Delta variant differ from the original disease? We consolidated studies as of September 2021 to highlight key differences between COVID-19 and the dominant variant. Sources include the CDC, Yale Medicine, and the University of California.
COVID-19 vs COVID-19 Delta Variant
At first glance, infections caused by the Delta variant are similar to the original COVID-19 disease. Symptoms reported from patients include cough, fever, headache, and a loss of smell.
But studies showed that the difference was in how quickly and severely patients got sick:
- Spread rate: How quickly the infection spreads in a community (based on the R0 or basic reproductive number). The Delta variant spread 125% faster than the original disease, making it potentially as infectious as chickenpox.
- Viral load: How much of a virus is detectable in an infected person’s blood, with higher loads correlating with more severe infections. Delta infections had a 1000x higher viral load.
- Virus detectable: How long after exposure a virus is detectable in an infected person’s blood. Delta infections were found to be detectable four days after exposure, faster than the original disease (six days).
- Infectious period: How long an infected person has the capability to pass on the virus to other people, from the first time they were exposed. Delta infections were contagious for longer than traditional COVID-19 infections, at 18 days compared to 13 days.
- Risk of hospitalization: How much more or less likely is an infection going to require hospitalization for treatment? Infections caused by the Delta variant were twice as likely to cause hospitalization compared to the original disease.
One other important finding from studies was that the existing COVID-19 vaccines helped against Delta infections.
The CDC found that approved vaccines reduced the rate of infection by 5x and the rate of hospitalization by 29x in a breakthrough case. They also found that overall efficacy against infection can wane over time, however, and at-risk people might require a booster vaccine.
What About Other COVID-19 Variants?
Delta is just one of many COVID-19 variants tracked by health officials, but it’s the one we know the most about.
That’s because reliable statistics and information on diseases requires thousands of cases for comparisons. We know a lot about Delta (and the once-dominant UK strain Alpha) because of how widespread they became, but there haven’t been enough cases of other variants to reliably assess differences.
As of September 2021, WHO was tracking 20 COVID-19 variants around the world with different classifications based on potential severity:
- 14 Variants under monitoring (VUM): Variants that are deemed to not pose a major global health risk, or no longer pose one.
- 2 Variants of Interest (VOI): Variants that affect transmissibility, virulence, mutation, and other virus characteristics, and are spreading in clusters.
- 4 Variants of Concern (VOC): Have similar characteristics to VOI but are further associated with a global risk.
Most of the current variants of interest and concern were first identified and labeled in late 2020, though 2021 variants are showing up as well.
|Label||Designation||Documented Origin||Earliest Identified Date|
|Alpha||Variant of Concern||UK||September 2020|
|Beta||Variant of Concern||South Africa||May 2020|
|Gamma||Variant of Concern||Brazil||November 2020|
|Delta||Variant of Concern||India||October 2020|
|Lambda||Variant of Interest||Peru||December 2020|
|Mu||Variant of Interest||Colombia||January 2021|
Should you be worried about all of these variants? For the most part, a lack of cases to provide clear information also reflects that they’re equivalent to or weaker than traditional COVID-19 infections.
But it’s important to note that our understanding of diseases and variants becomes more nuanced and accurate over time. As research continues over a longer timeline and over a wider database of cases, expect information on COVID-19 variants (and any disease) to become more concrete.
Charted: Average Years Left to Live by Age
Visualizing the number of years left to live for Americans at every age, reveals the broader trends in American life expectancy.
How Many Years Do You Have Left to Live?
At the start of the 19th century, when there fewer than 1 billion humans on the earth, global life expectancy at birth stood at roughly 29 years.
This is a startlingly low figure—because life expectancy is a statistical projection of how many more years a person can expect to live, based on the mortality rates at the time. And since the infant mortality rate in particular was so high, life expectancies accurately summarized the low likelihood of many babies living to adulthood.
However, since the 1920s, life expectancy across all ages has improved leaps and bounds, thanks to rapid advancements in nutrition, healthcare, and sanitation.
We visualized the current American life expectancy by age and gender, using data from the Office of Social Security, which bases their current projections on 2020 mortality rates.
American Life Expectancy at Every Age
A key takeaway with life expectancy is that it increases as one gets older. This is easily seen in the table below, which lists the remaining years left to live at a given age for an American male and the projected life expectancy.
|Age||Years Remaining (Men)||Life Expectancy (Men)|
At birth, an average American baby boy can expect to live till just past 74. But if the boy reaches adulthood, then at 21 he might live to a full year more, past 75. This trend persists even towards the end of life when the years we have left drop rapidly, influenced by the higher likelihood of death.
American women, on the other hand, have a higher life expectancy than men. At birth the gap is close to six years, narrowing steadily to around one year by 85.
Interestingly, women outlive men in nearly every country in the world, due to a mix of sociological, behavioral, and biological reasons.
COVID-19: Reversing A Decade of Increasing American Life Expectancy
While the current American life expectancy at birth seems reasonably high, it is nearly two years lower than the 2022 figure which used the 2019 mortality rate. It is also lower than the life expectancy at birth in 2009, which used 2005 mortality rate.
at Birth (Men)
at Birth (Women)
American mortality rates went up 17% between 2019–2020, in part because of COVID-19, in turn affecting life expectancy. The U.S. also had a higher COVID-19 mortality rate compared to its peers two years after the pandemic first struck.
Thus, American life expectancy may not improve immediately to 2019 levels, which can affect insurance premiums, pension benefits, and plans.
Misc6 days ago
Ranked: America’s Best Universities
Technology2 weeks ago
Ranked: Largest Semiconductor Foundry Companies by Revenue
Automotive2 weeks ago
Visualized: EV Market Share in the U.S.
Maps1 week ago
Interactive Map: The World as 1,000 People
Retail1 week ago
Ranked: Average Black Friday Discounts for Major Retailers
Brands1 week ago
Ranked: Fast Food Brands with the Most U.S. Locations
Economy1 week ago
Visualizing 30 Years of Imports from U.S. Trading Partners
Markets1 week ago
Ranked: The Biggest Retailers in the U.S. by Revenue