What makes the Delta variant so contagious?

Published: Jul. 29, 2021 at 1:23 PM CDT
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BIRMINGHAM, Ala. (WBRC) – The Alabama Department of Public Health (ADPH) is aware of 300 confirmed cases of the Delta variant in the state, but the true number is likely much higher, said Dr. Scott Harris.

Variants of COVID-19 are identified through a process called viral genome sequencing. This advanced testing is happening in about a dozen labs in Alabama, including UAB’s Fungal Research Lab. Scientists there discovered the Delta variant in late April. By mid-June they’d found 5 more cases. Last week, 82 of the 91 samples sequenced were the Delta variant.

READ: UAB lab tracking variants of COVID-19

“The worse thing about this variant is its infectiousness. It’s very, very hard to avoid it if you are exposed to it,” said Dr. Jeanne Marrazzo, Director, Division of Infectious Diseases, UAB.

Dr. Marrazzo said it’s getting harder to avoid the Delta variant in Alabama and said it’s behind the sharp uptick in cases and hospitalization.

Daily cases have topped 1,000 for the past week and hospitalizations are surpassing rates not seen since February.

“We should assume that most COVID disease in our community now is the Delta variant,” said Dr. Wesley Willeford, Medical Director of Disease Control, Jefferson County Department of Health.

Researchers in China traced an outbreak caused by the Delta variant and found the virus spread more quickly than the original strain of COVID-19 because people infected with this variant had many more copies of the virus in their respiratory tracts.

“The thing that that study looked at, the number of viral copies that were taken out of a sample from a person and on average, what they found was there’s about 1,000 times more viral copies per person who was infected with the Delta variant,” explained Dr. Willeford.

He added, “What that translates to, is the way I think of it, that’s like an increased dose of the virus per breath, per sneeze, per cough, whatever happens that get COVID out of your body. So, each person who is infected with the Delta variant, unfortunately is able to spread it more effectively because there’s just more virus in each droplet.”

Dr. Willeford said there’s not enough research to determine if people are getting sicker with the Delta variant, but he said there’s evidence people are getting sick more quickly.

“In that study [out of China], one of the things they noticed was the time to illness after exposure was much shorter. Previously, it had been about 6 days to really feeling sick or testing positive with the original strain. In this case, it’s about 3 to 3.7 days. So, it’s a much quicker time that we start to feel sick after exposure because we’ve gotten a higher dose and our body’s immune system is finding that more quickly, and acting on that more quickly.”

Dr. Willeford said India’s healthcare system was overwhelmed when the Delta variant spread across the country with “a lot of people getting sick very quickly.” Dr. Marrazzo said hospitals in Alabama are already starting to feel the impact of this variant.

“You might remember at our peak we were caring for over 3,000 in-patients, hospitalized for COVID and that just about broke our system. So, when you think about us going from 500 [in-patients] to over 800, that is why we are doing this today, and why we are really getting concerned.”

How much protection do the available COVID-19 vaccines offer against the Delta variant?

“If you are fully vaccinated, that is you have 2 doses of one of those vaccines [Pfizer or Moderna], it’s about 90% effective, it’s really quite good. Doesn’t mean it’s 100%. There’s almost no vaccine that’s 100% but 9 out of 10 people who get 2 doses of those vaccines, or either of those vaccines, is going to be protected against the Delta variant,” said Dr. Marrazzo.

The Johnson and Johnson vaccine offers about 70-80% protection against the Delta variant, said Dr. Marrazzo, but added, “it’s still quite good.”

“It’s really important now to make sure you get vaccinated with, ideally the mRNA vaccine, but that you get the 2 doses. The Delta variant is just nothing to be toyed with, you really want to make sure that you have as much of your defenses in line against it as much as possible.”

What do you say to young people who are not getting vaccinated because they think their risk of complications is so low?

“The biggest thing I would point out is COVID-19 can have unexpected symptoms in anyone of any age. We’ve seen pediatric patients be hospitalized, we’ve seen pediatric patients go into the ICU. We’ve certainly seen 20-to-40 year olds land in the hospital with this virus and I always want to say, that is largely preventable, that’s almost entirely preventable in those young people who can receive the vaccine. And, this is kind of the argument I make to people. I say, ‘Look at your status when it comes to insurance, your ability to pay for unexpected medical costs,’ and unfortunately, healthcare in the United States is very expensive. Landing in the hospital, even with a good insurance, is probably going to result in several thousand dollars of out of pocket costs, and I always tell people, ‘Look how a free vaccine can prevent something like this from happening.’”

He added, “It really is as the old saying goes, an ounce of preventions worth a pound of cure. Even if you view that as a lower risk, if it does happen, gosh, it’s going to be incredibly disruptive to your life if you land in the hospital and get really sick, which can happen with COVID-19. Getting that vaccines, really takes all that off the table. It really removes the chance from really even being a possibility for a younger person.”

Can a person be infected with the Delta variant within seconds?

“I know I’ve heard that bandied about, but I haven’t found a good source for that,” said Dr. Willeford. “I think it’s because there’s such a high dose it’s going to take less time, but where does it fall in that seconds to 15 minutes range? I don’t think we know exactly, because again that’s hard to pin down precisely. I think that 15 minutes, 6-feet rule is still decent to work off of for the time being. I expect the Centers for Disease Control and Prevention will probably continue to evaluate that and see if that makes sense. Does it make more sense to be 6-feet 10 minutes, or 6-feet 5 minutes? Don’t know yet. But I think when you’re dealing with a virus that’s easier to pass than the original strain, there’s some part of that 6-feet 15 minutes rule that may have to be altered in the future.”

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