Delta variant may cause steep increase in cases, deaths in fall, models show

LOS ANGELES - As cases of the novel coronavirus and its delta variant continue to increase, a new projection model shows there are no signs of the hyper-contagious variant slowing down — foreshadowing that the pandemic may not be over as quickly as many hoped.

The projections, released Wednesday by the COVID-19 Scenario Modeling Hub, show a continued and accelerated increase in cases and deaths, with numbers peaking in mid-October. 

The latest projections combine 10 mathematical models to create an ensemble projection, with four scenarios. The scenarios are based on how much of the population gets vaccinated and how quickly the variant spreads.

Researchers at the hub work with the U.S. Centers for Disease Control and Prevention to help the agency track the pandemic, and the new model suggests daily deaths could triple from current numbers.

In the most likely scenario, the U.S. reaches only 70% vaccination among Americans and the delta variant is 60% transmissible, Justin Lessler, an epidemiologist at the University of North Carolina who helps run the modeling hub, told NPR.

Lessler said in this scenario, at the peak in the fall, there would be around 60,000 cases and around 850 deaths per day.

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While there are uncertainties, such as increased vaccinations or mitigation measures, that could impact the projections, the data comes as teachers prepare to send students back into classrooms and businesses prepare to bring employees back into offices.

Cases of the delta variant are soaring in many countries. The delta variant — which is more than 200% more transmissible than the original coronavirus — is also pushing cases up in the United States.

In addition, a new study suggests the viral load is 1,000 times higher than the original strain of the virus.

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The delta variant is a mutated version of the novel coronavirus that spreads more easily than other strains. It now accounts for an estimated 83% of COVID-19 cases in the United States as it continues to surge largely among unvaccinated populations, officials said. 

A recent study published on July 7 and led by Chinese epidemiologist Jing Lu at the Guangdong Provincial Center for Disease Control and Prevention in Guangzhou, China shed light on why the delta variant is of grave concern to the world’s health care system and why it is more transmissible than other mutations. 

Researchers found that the delta variant contains 1,000 times more viral material than that of the original novel coronavirus variant that infected much of the global population during the onset of the global pandemic last year. 

This means the delta variant can replicate at a much faster rate than the original strain, making the mutation much more infectious, according to the study. 

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During a White House press briefing last week, CDC Director Dr. Rochelle Walensky said cases in the U.S. were up about 70% over the last week, hospital admissions were up 36% and deaths rose by 26%.

"There’s a clear message that is coming through: this is becoming a pandemic of the unvaccinated," Walensky said. "We are seeing outbreaks of cases in parts of the country that have low vaccination coverage because unvaccinated people are at risk. And communities that are fully vaccinated are generally faring well."

As of July 23, 2021, more than 162 million people in the United States had been fully vaccinated against COVID-19.