Testing results released this week show that the novel coronavirus was circulating in the United States and killing Americans weeks earlier than previously thought. The failure to recognize these early cases led officials to act on faulty assumptions and without the necessary urgency. As a result, the virus spread widely.

In that case, the federal government acted based on the flawed information it had. It acted as if there were no way that something was missing. Others followed its guidance, and COVID-19 was allowed to spread for weeks until stay-at-home orders were issued en masse.

We can’t afford to have something like that happen again.

Months now after the coronavirus appeared in China and then was detected in the U.S., there is still a lot we don’t know about it. We should be wary about sweeping statements regarding what activities are safe, and cautious about allowing more than essential movement to take place.

First off, we don’t have a good grasp even now on how deadly COVID-19 is, or why death rates vary so much across regions.

As of mid-April, the death rate in Italy was about 13 percent. In the U.S., it was around 4.3 percent. It was 0.7 percent in Wyoming but 7 percent in Michigan.

Part of the trouble comes from the testing, which has varied in number and targeting across regions, and has been too low almost everywhere. More testing could reveal a high number of infected people who survived, driving death rates down.

Or it could reveal additional deaths attributable to the virus. Total deaths have soared in virus hot spots such as New York and Massachusetts last month, indicating that some caused by COVID-19 aren’t being reported as such.

Antibody testing, which can show whether a person has had COVID-19 and recovered, has been conducted in Germany, the Netherlands and parts of the United States. It found that anywhere from 2 percent to 30 percent of the population may have already been infected. Higher numbers likely mean that the virus is less deadly, but also that are many asymptomatic carriers who may spread the disease unaware that they have it.

Adding more uncertainty, many experts have criticized that study, and say the antibody test may not be accurate.

Speaking of antibodies, we don’t know yet what level a person must carry to be protected from getting the disease again, or how long that protection may last.

There are hopes that aggressive antibody testing could allow millions of Americans to go back about their lives with some normalcy, secure that they will be safe. That may be wishful thinking.

We also don’t know all of COVID-19’s symptoms; heart damage and a blood-clotting problem are just two mysterious ones suggested recently.

We don’t know how airborne the virus is, or how well it travels, outdoors and indoors. We don’t know whether it will die off in the summer, though that seems unlikely.

What we don’t know matters. In early February, convinced that the novel coronavirus was not circulating in the United States, the Trump administration instead focused on restricting travel from China. Scarce testing capacity was prioritized on people who had traveled recently to Asia.

We now know they were wrong, and that the focus on travel-based transmission wasted weeks that could have been spent on containing cases already in our communities.

Now, some states are rushing to reopen businesses. Officials say they can do it safely.

But we don’t know enough about COVID-19 to say that with any confidence. The only thing we know for sure is that we must proceed with the utmost caution.