With Wisconsin’s Supreme Court order nullifying Gov. Tony Evers stay-home order last week, we are in what feels like a new world.

Some communities have opened fully. Others imposed orders, and then many dropped them. Some big counties remained closed.

Around the state, we are seeing bars and restaurants, long-shuttered, suddenly open. Same with stores of all sorts. At least one city close to the border saw a rush of residents from still-closed Illinois this weekend.

Experts urge caution and ask the public to consider risk when deciding what to do with this new freedom. They are guided by science on the spread of infectious diseases. Here is what several experts wanted people to know:

First, it’s all about the dose of coronavirus you’re exposed to

Think about this equation from Erin Bromage, a professor at the University of Massachusetts Dartmouth: Exposure, coupled with time, equals the “dose” of the virus that will make its way into your body.

Although experts aren’t totally sure yet just how big a dose of this particular virus can cause you to become sick, they estimate it could be fewer than a thousand particles.

For comparison, the dose needed to get sick with another coronavirus, Middle East Respiratory Syndrome, could be as high as 10,000 particles.

he time element of the equation makes sense on its face — the longer you spend in an environment where the virus is moving around, the more likely you are to get enough of it to become infected.

But what about exposure?

It depends on what action caused the virus particles to make their way to you. According to Bromage, a breath from an infected person would release 20 particles in the air per minute. Speaking face to face would release about 200 particles per minute, and sneezing or coughing would release a colossal 200 million particles all at once.

The equation for this virus says, then, if an infected person is breathing near you, it would take 50 minutes of exposure at least for the virus to make it into your lungs. If you’re talking, it can happen much faster, in just five minutes.

The risk grows in certain environments

Any time you turn up one part of the equation or another, the risk climbs.

Talking for hours over dinner in a crowded restaurant could theoretically sicken dozens of people, because you’re speaking (which emits more virus particles than breathing) for an extended period of time. It’s also in a confined space, which ups the risk.

Situations that place you in close proximity with others for longer amounts of time — like a shared office, a music concert, a movie theater, the aforementioned restaurant or flying on a plane — lend themselves to a greater risk of infection.

There are sneakier risks, too, like the example of a choir practice in Washington state that sickened 53 people with COVID-19 and killed two — despite the fact that they tried to leave space between each other.

Why? The act of singing sends more particles into the air than talking, and they practiced for more than two hours. It’s why one Wisconsin pastor said although in-person services might resume, his congregation likely won’t be cracking open their hymnals together until a vaccine is developed.

In contrast, the grocery store, which many of us have feared for months, can actually be a low-risk situation if you’re shopping safely. If you get in and out without speaking much to others, you’ve decreased both your possible exposure from an infected person and the time spent in one space.

This is different, of course, for employees, who spend hours in the store.

What we know about past diseases helps us understand how coronavirus spreads

The question of how coronavirus spreads can’t be answered by controlled studies, because it would be unethical to force people to contract the virus so researchers could map how it travels.

Thus, this science is imperfect. But the exposure-and-time element is backed by what we know about diseases such as tuberculosis and measles, in which you increase your risk for infection based on how long you’re exposed, according to Jonathan Temte, associate dean for public health and community engagement at UW-Madison’s School of Medicine and Public Health.

For example, people susceptible to getting COVID-19 are often in households with someone who already has it, putting them at risk of a high dose and prolonged exposure to the virus.

And it’s best to use the information we’ve got from history versus using nothing at all, Temte added.

“We have no collective experiential knowledge of this,” he said. “Going forward, we have to use all the tools that we have.”

So, here’s what’s next

There is a strong, worldwide focus on creating a vaccine but experts cautioned that a vaccine is more of a hope than a plan at this point. They don’t expect one soon, maybe months or even years.

In the meantime, we are left to tactics to try to slow and manage the spread of COVID-19.

There has been a growing recognition among some scientists that lockdowns could not continue indefinitely, but those same experts are deeply concerned this new freedom without precautions could create a rush of cases that could overwhelm the health system.

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