What To Know About The Delta Variant This Summer

Worldwide attention is on a more contagious variant of the COVID-19 virus called ‘Delta.’ Infectious disease specialists with Rochester Regional Health explain what it is and if it puts you at more risk.

Jul. 23, 2021 3   min read

As summer begins, millions of people are readjusting to life after the worst of the COVID-19 pandemic seems to have passed in the United States. Nearly 60 percent of the country’s population has received at least one dose of the COVID-19 vaccine and the number of new COVID-19 cases per day has fallen to levels that match the numbers in March 2020.

Of the new cases, a growing number appear to be linked to the Delta variant. Variants are different versions of a virus that grow like branches on a tree; each one is different than others but share the same roots and trunk.

Emil Lesho, DO, and Edward Walsh, MD, are Infectious Disease specialists with Rochester Regional Health. They provided some insight into the variant, how prevalent it is in the Rochester area, and how much cause there is for concern.

What is the Delta Variant?

The COVID-19 virus has more than 200 variants. According to the CDC, there are four notable variants in the U.S.

  • Alpha (B.1.1.7)
  • Beta (B 1.351)
  • Gamma (P.1)
  • Delta (B 1.617.2)

Each of the variants is notable because it spreads more quickly and easier than the original virus.

“Some mutations are nothing, some mutations are actually harmful to the virus, and some mutations make the virus more of a problem for us,” Dr. Lesho said.

The Delta variant is the most contagious strain of the virus and can spread up to 225 percent more quickly than the COVID-19 virus, according to U.K. scientists.

When did Delta first appear?

Early reports of cases involving the Delta variant began to surface in India back in December 2020. It spread and cases started to spring up in March 2021, according to CDC researchers.

As of early July, experts estimate more than half of all COVID-19 cases in the U.S. are linked to the Delta variant. Testing from the public health laboratory Wadsworth Center has confirmed cases involving the Delta variant are present in the Rochester area. Experts estimate approximately 30 percent of new COVID-19 cases in the area are due to the Delta variant.

“It represents a small but appreciable percentage of cases that are occurring locally,” Dr. Walsh said.

“By the end of the summer, we estimate around 90 percent of the new cases are going to be caused by Delta,” Dr. Lesho said.

How effective is the COVID-19 vaccine against variants?

The good news is that research shows the Pfizer-BioNTech, Moderna, and AstraZeneca COVID-19 vaccines protect against the Delta variant, as well as other variants.

“If you’re fully vaccinated, you’re good to go against the Delta. If you get infected with the Delta, you might have mild symptoms and that’s about it,” Dr. Lesho said.

“I think the Delta variant is just another reminder of how important it is to get vaccinated. If you’re get vaccinated, it’s not a big deal. But if there are a lot of people who give the virus an opportunity…then you don’t know what could happen.”

Currently, 99.5 percent of all COVID-19-related deaths are happening with people who have not been vaccinated against the virus. Dr. Lesho and other experts strongly encourage people who may not have received their COVID-19 vaccine to get one to protect their health and others around them.

There are many resources to help find a vaccine, including:


If you or someone you know is experiencing symptoms of COVID-19 such as a cough, runny nose, fever, chills, or new loss of taste or smell, take the next step to see how to get tested.

Getting Tested
covid19 icon