Herd immunity generally happens when 70% to 90% of a population becomes immune to an infectious disease — either because people have been infected and recovered, or because they’ve been vaccinated.

There’s also no cure for the novel coronavirus. So the only way to control this deadly pandemic is through personal behavior — like staying 6 feet away from others, including in social settings, and wearing a face mask.

“It is critical that we all take the personal responsibility to slow the transmission of Covid-19 and embrace the universal use of face coverings,” Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said Tuesday.

I’m young and healthy, so I’m not worried

“Specifically, I’m addressing the younger members of our society, the millennials and the Generation Z’s,” Redfield said in calling for face coverings. “I ask those that are listening to spread the word.”

In Florida, the median age group for those infected back in March was people in their 60s. But in the past few weeks, that median age has plummeted to young adults in their early 30s, Gov. Ron DeSantis said in late June.

During their night out, the virus seemed “out of sight, out of mind” because they didn’t know anyone who had contracted it, Crisp said. The group also had a false sense of security, she said, because their governor said it was safe to reopen.

“I feel foolish. It’s too soon,” Crisp said.

Days before his diagnosis, Gobert had made light of the pandemic when he jokingly touched every microphone during a news conference.

He later publicly apologized and urged the public to not fall into a false sense of security like he did.

We’re checking the temperatures of all employees / customers / party guests

I don’t need to wear a mask

“As economies open up more, masks become more important, not less important,” said Jeremy Howard, a research scientist at the University of San Francisco.

Howard has spent much of the past four months in Texas, where he noticed the use of face masks dropped as the state started reopening.

US Surgeon General Dr. Jerome Adams said if you want more businesses to reopen and stay open, wear a mask.

“Face coverings → less asymptomatic viral spread → more places open, and sooner! Exercise and promote your freedom by choosing to wear a face covering!”

The rate of deaths is decreasing, so things are getting better, right?

“Our daily case/new infection rate has really skyrocketed to over 40,000,” said Dr. Jonathan Reiner, a professor at George Washington University School of Medicine.

First, deaths from Covid-19 often lag weeks behind new infections. It can take up to two weeks for symptoms to appear. After that, people might not get tested immediately. Then, it can take even longer for severe cases to require hospitalization.

“It takes about a week after someone becomes infected until they get sick enough to be hospitalized, and then often about a week after that until you start seeing deaths,” Reiner said.

“We’ve sort of plateaued with the death rate sort of fluctuating between 600 and 800 deaths per day. … Obviously, everyone is concerned about the death rate starting to take off again.”

With the current rates of transmission, “we will reach 100,000 cases per day” in the US, said internal medicine specialist Dr. Jorge Rodriguez.

With this virus, “one person — on the average — infects three people, and we’re already at 40,000” new cases reported daily, Rodriguez said Tuesday.

I’ve already tested negative, so I’m fine

That’s not an excuse to stop taking precautions.

“Because it is possible to get a negative result even when you have coronavirus, it is important to be careful even when you receive a negative result.”

Even if a negative test result is correct, you may have been infected since that test was taken.

Maybe we should just let nature take its course and get herd immunity

That’s not a good idea because some intensive care units are already at or near capacity, Rodriguez said.

And that could reduce care for anyone else who needs it — such as car wreck victims or people suffering from heart attacks.

“People are being admitted to hospital beds and being admitted to ICU (intensive care unit) beds faster than they’re being discharged” due to the coronavirus, said Will Humble, executive director of the Arizona Public Health Association.

Humble said he’s worried hospitals will go into “crisis standards of care,” which basically means “lower care for everybody, not just people with Covid-19.”

But the CDC director said everyone can help stop this deadly pandemic. It just takes personal responsibility.

“We have powerful tools at our disposal — social distancing, wear a face cover in public, and be disciplined about the frequent hand washing,” Redfield said.

“We are not defenseless against this disease.”