Maybe there’s an explanation other than the markets.

Maybe it was simply optimism — unfounded optimism, but optimism nonetheless — that spurred President Trump to repeatedly and consistently play down the threat that the novel coronavirus posed to the United States.

Maybe his insistence that the virus was under control, that the number of cases would dwindle to nothing, that the death toll would remain low — maybe all of this was Trump embracing the small chance that things would work out for the best. Maybe his advisers were even saying, “Hey, this thing could just dissipate in the spring the way the seasonal flu does.” Maybe it was a choice to elevate that optimism instead of focusing on the growing shadow covering the country.

Or maybe it was the markets. Trump obviously recognized the threat that the virus posed to the economy, which is why his early comments on the subject often focused on the link between the two. Even as the number of cases mounted and the Dow Jones industrial average and S&P 500 began to stumble, Trump insisted that the best case was inevitable. Last week, he told the country to “stay calm” because the virus would simply “go away.” When his news conference Friday spurred a rally on Wall Street, Trump signed a printout of the turnaround and sent it to Fox Business host Lou Dobbs.

It was short-lived. Even after the Federal Reserve slashed interest rates again over the weekend, the stock indexes fell dramatically Monday, the second-biggest drop in history. When Trump came to the lectern in the White House briefing room to discuss the virus, his tone was noticeably different than it had been even a day earlier.

For the first time, Trump’s obvious focus wasn’t on playing down the threat of the virus. As he outlined a set of proposals aimed at halting the spread of the virus by encouraging people to isolate themselves, his tone was quieter and his language more direct. Reading from a prepared statement, he largely avoided the sort of praise for his own leadership that has been a regular feature of his coronavirus briefings. His focus, instead, was on the recommendations — recommendations that mark a startling new moment in the United States, however inevitable they may have been.

Even given the opportunity to riff on the subject in a question-and-answer session with the news media, he largely stuck to the sober assessments with which he’d begun.

Asked how long the threat of the virus might linger, he didn’t say that it would go away quickly but, instead, that it might last until late summer. Asked whether the economy might be headed into recession, he said that in fact, it might. When it was noted that a staunch ally, Rep. Devin Nunes (R-Calif.), had called on people to go out to eat, Trump said he disagreed with that advice, in keeping with the guidelines he had just offered. He played down a feud with Gov. Andrew M. Cuomo (D-N.Y.) on Twitter, explaining that he thought it was “very important that all of the governors get along very well with us.” He even said that he thought the media actually had been “very fair.”

Importantly, he didn’t dismiss the danger posed by the virus.

“This is a bad one. This is a very bad one,” Trump said. “This is bad in the sense that it’s so contagious. It’s just so contagious.”

Asked whether he had spoken about the virus with his teenage son, Barron, Trump said he had.

“He says, ‘How bad is this?’ It’s bad. It’s bad,” Trump said. “But we’re going to be, hopefully, a best case, not a worst case. And that’s what we’re working for.”

It’s important to note that there were flashes of Trump’s past approach to the situation. He disagreed with Nunes but gave a pass to Gov. Kevin Stitt (R) of Oklahoma, who had similarly encouraged people to eat out but whose state, Trump said, “doesn’t have a tremendous problem.” While his advisers were encouraging young people to stay home instead of going out, he again reiterated that young people weren’t at as much risk as older Americans — a true statement but one that has seemingly undergirded broad disregard for social-distancing measures by younger people.

Nor was praise for his own efforts completely absent. Asked how he would rate his administration’s response to the virus on a scale from 1 to 10 — a setup if there ever was one — Trump gave the answer you would expect: a solid 10.

Broadly speaking, though, Trump’s approach to the issue was more sober than at any point since he began participating in these briefings about three weeks ago. One week ago Monday morning, Trump downplayed the number of coronavirus cases on Twitter, comparing it with the seasonal flu. One week later, with the number of confirmed cases over 4,000 and the number of deaths over 70, Trump’s Twitter feed had a different focus.

It’s been obvious for some time, given the rate of growth in confirmed cases and given the effects of similar rates of growth in countries such as China and Italy, that Trump’s public optimism was not sustainable. Hoping for the best is a perfectly fair approach to a situation, and aiming to calm the nerves of Americans and, to a lesser extent, investors is one of the roles the president plays. But after a while, optimism can tip into denialism. One day after insisting that the situation was under control — a reference, he said Monday, to his team’s work and not the virus itself — Trump addressed the outbreak with uncharacteristic sobriety and accuracy.

Of course, this, too, might be what’s best for the markets. The recent slide has been a function of concerns about the repercussions of the virus’s spread. Hearing that a recession looms and that the worst effects might last for months is not something that’s going to spur people to dump a bunch of money in stock futures. But working to limit the virus’s effect on the economy by holding down the number of concurrent infections is the new best-case scenario.

We’re not getting out of this with a few hundred infections; we’re well past that. We might get out of it without the health-care system hitting a point of saturation, and we might get out of it with thousands and not hundreds of thousands of deaths. We might get out of it by August instead of next April. We might get out of it and recover quickly, or we might not. It may depend on how much people listen to Trump right now.

Trump doesn’t use a sincere, somber tone very often, so it’s a bit hard to know how to read it. On Monday he even sounded a bit — worried. If that’s how he feels, it’s good news. It’s a moment for worry, and worry, experts tell us, offers the best path forward.