Q&A: What experts know about the delta variant

As COVID-19 cases rise, public health experts are encouraging vaccination and a return to mask-wearing.


Christine Petersen poses for a portrait. (Contributed)

Lillian Poulsen, News Reporter

Iowa is experiencing a surge in new COVID-19 cases, as the highly transmissible delta variant of the virus rapidly spreads through the state and the nation overall.

In recent weeks, Iowa has seen a steady increase in the number of COVID-19 cases, hospitalizations, and deaths — despite having seen a decline previously.

According to the Centers for Disease Control and Prevention, most of Iowa’s counties — including Johnson County — had high levels of community transmission of COVID-19, as of Aug. 18. Only one Iowa county, Appanoose, has a moderate rate of transmission.

“All of us are worried about delta because of this high level of transmission — it makes it that much more likely that we are going to start seeing changes that could lead to less effectiveness against the virus,” said Christine Petersen, director of the Center for Emerging Infectious Diseases in the University of Iowa College of Public Health.

The Daily Iowan sat down with Petersen to ask her about the delta variant.

Question: Why has the delta variant spread so quickly?

Answer: The delta variant arose in India during spring 2021, spreading to over 60 countries by the beginning of June, according to CNBC.

In early reports, researchers found that the variant was more transmissible in people who were infected, Petersen said. Delta doubled the ability of one infected person to infect more people, from about two to five people per one infected.

Petersen said this level of infection is about the same as that of chickenpox—which is highly infectious. Along with this discovery, she said, researchers learned that people are spreading more virus particles than before.

“A person who’s infected has between five and 10 times more virus coming out of their airway when they cough, sneeze, or breathe,” Petersen said. “That person is putting a lot more virus out into the air and the environment, leading to more people getting infected.”

Related: Public health experts encourage second dose in face of delta variant

Q: Who is most at risk for infection?

A: People who aren’t vaccinated are at a much higher risk of getting infected anytime they are in a room with people who are shedding the virus, Petersen said.

Additionally, people who are more susceptible to contracting the virus, regardless of vaccination status, are more likely to get infected with the delta variant.

“Some people, perhaps who don’t have as good an immune system or have as good of an immune response shed enormous amounts of virus,” Petersen said. “People with delta are very infectious and that’s who can lead to a super spreader event.”

Q: Who should get tested for COVID-19?

A: If someone had signs or symptoms of COVID-19, regardless of whether they’re vaccinated, they should get tested, Petersen said.

“You should definitely get tested because then you know if it’s the virus or another respiratory illness,” Petersen said. “It also helps set up health practices like isolation and quarantine and tracing the people that you’ve been in contact with to let them know that you’re positive and that they should be watching for signs and symptoms.”

If someone is exposed to the virus without being vaccinated, they will have to quarantine, Petersen said.

Related: Local and state health officials urge Iowans to get vaccinated as delta variant gains strength

Q: Should everyone be worried about delta, even if they’re vaccinated?

A: The high level of transmission of the delta variant makes it much more likely that the vaccine would be less effective against the virus, Petersen said.

“The vaccine does work quite well against the delta variant,” Petersen said. “It might have slightly less efficacy than against the original types of virus that it was originally made for and tested against, but it’s hard to know by how much.”

The original effectiveness rate of preventing severe disease and hospitalization in the vaccine, about 95 percent, is down to 70 to 80 percent in the delta variant, she said.

Researchers in Provincetown, Massachusetts, found that people reported symptoms even when they were vaccinated, according to NPR.

“People, regardless of their vaccination state, had equal amounts of virus in their bodies,” Petersen said. “When we look at whether or not the vaccine works, the vaccine was proven to work to prevent clinical disease, hospitalization, and death.”

Q: Who should wear masks?

A: Everybody should wear masks, regardless of vaccination status, Petersen said.

People should also avoid gatherings where they might be encouraged to take off their masks, she said.

“It’s highly encouraged not to eat or drink in front of a lot of people, so you don’t have to take your mask off,” Petersen said. “Going out to bars is not a good idea.”

It’s especially important for people who aren’t vaccinated to continue practicing health and safety measures, Petersen said.

“If you’re not vaccinated, you should be doing all the measures we were doing a year ago, which are social distancing, staying away from crowds, and always wearing a mask in any sort of crowded condition—even if that’s outside,” Petersen said.

Q: How do these measures, like vaccination and wearing masks, prevent the transmission of this virus?

A: These measures decrease the chance of severe infection and the rate of infection within the community, Petersen said.

“They decrease the rate of infection that you’re going to have overall, creating a phenomenon called herd immunity — you have less people in a population who can spread the virus, making the amount of spread within the community less,” Petersen said.

Social distancing and avoiding crowds also help, she said.

“Social distancing makes it harder to have an interaction that can lead to viral particles moving from one person to another,” Petersen said. “Being cognizant of the people you’re around and not mixing with too many people or having a bubble also help decrease the amount of sharing of viruses through a community.”

Despite these precautions, nothing can completely stop the virus except for staying home, she said.

“No one precaution is 100-percent foolproof,” Petersen said. “In order to best protect you, your loved ones, and the small kids who are younger than 12 and not vaccinated, you are going to want to use the multi-layer approach so the chances of the virus entering is very limited.”

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