After declining steeply for six months, coronavirus cases are once again on the rise, thanks to the delta variant. The Centers for Disease Control and Prevention reported Friday that new cases are up by nearly 70% in just a week. Hospitalizations are up by nearly 36%.

Surges are most pronounced in areas where vaccination rates are low, but there are also increases in places such as Los Angeles and New York City. And health officials are once again urgently pressing unvaccinated Americans to get the shot.

«This is becoming a pandemic of the unvaccinated,» said CDC Director Dr. Rochelle Walensky at a briefing Friday. «If you remain unvaccinated, you are at risk.»

But if you’re already vaccinated, how worried should you be? Are new precautions called for? Here’s what to know about the fast-spreading variant and how to stay safe and protect others.

How much more contagious is the delta variant, really?

Very. As NPR has reported, delta appears to be about 225% more transmissible than the original SARS-CoV-2 strains. One recent preprint study from China found that people who are infected with delta have — on average — about 1,000 times more copies of the virus in their respiratory tracts than those infected with the original strain, and are infectious earlier in the course of their illness.

No matter how you look at it, delta seems to spread faster, explains Helen Chu, associate professor of medicine at the University of Washington.

«You can look at it through modeling, you can look at it through population-level data, and you can look at it simply by putting the virus into the cell and looking at how quickly it infects the next cell,» she says. «In all of those measures, it has looked like it’s more transmissible.»

If I’m vaccinated, can I get sick with delta?

Yes, but don’t panic. The vaccines are effective against the delta variant, and though it’s still possible to get infected, the vaccines dramatically reduce the risk of serious illness that leads to hospitalization or death. A study from the U.K. found that the Pfizer vaccine is 96% effective against hospitalization from the delta variant after two doses.

For context, the CDC has documented a total of 5,492 cases of fully vaccinated people who were hospitalized or died from COVID-19, among the 160 million people have been fully vaccinated in this country.

It’s not clear how many of these breakthrough infections are from delta variant cases, but it has quickly become the dominant variant in circulation.

Though the CDC only tracks breakthrough infections that lead to hospitalization and death, some states are keeping track of every case, even the mild ones. In Massachusetts, there have been about 4,450 confirmed breakthrough cases or about .1% of all vaccinated people, as WBUR reported.

Does delta cause different COVID-19 symptoms?

Maybe. Some doctors and public health departments have reported that people infected with delta have different symptoms from the original, classic signs of COVID-19: cough, loss of taste or smell, and fever. Now, some of the more common symptoms appear to be runny nose, sore throat and headache, according to the ZOE COVID Study, an ongoing app-based research project based in the U.K.

But Chu warns that it’s hard to know what’s behind that apparent change, «because the population that it’s infecting is not the same population that was infected in the prior waves,» says Chu. The people getting sick now tend to be much younger, she says.

Since COVID-19 might present differently in younger people, any changes in symptoms could have less to do with the new variant and more to do with the people who are contracting it. «I don’t know that you can disentangle that,» Chu says.

«This is already a disease that produces a pretty broad range of different clinical presentations in people,» adds Rasmussen. She’d like to see better data before concluding the symptoms are, in fact, different.

What about kids? Can kids get infected and spread delta?

Yes. Although children tend to have more mild cases of coronavirus, they are certainly susceptible to infection. Children remain the least protected age group, since the vaccine is not authorized for children under the age of 12.

It’s possible that children who get infected with the delta variant might have more symptoms than they would if they were infected with an earlier version of the virus. With a more transmissible variant, «when someone gets sick, they tend to have more virus, and they tend to have more symptoms,» Chu explains.

That being said, Chu says, typically «children are not that symptomatic from COVID.» Her best guess? She thinks delta «probably will not lead to significant numbers of children getting hospitalized.»

But there’s still a reason to keep your kids masked up in public, and that’s the risk they could spread it to more vulnerable people, says Rasmussen. «Even if it doesn’t impact them, it could impact other vulnerable people in their household, such as people who may not have had a robust response to the vaccine, people who are immunocompromised.»

Aubrey, A., & Simmons-Duffin, S. (2021, July 17). With The Delta Variant Spreading Fast, Is Time To Mask Up Again? NPR. https://www.npr.org/sections/health-shots/2021/07/17/1017075240/delta-variant-is-spreading-fast-and-new-cases-are-rising-is-time-to-mask-up-agai.