Thursday’s White House coronavirus briefing was a contentious one, as President Trump snapped at reporters in the room and took shots at his political rivals, but it also brought some scientific news about the virus and what could make it less infectious. Here are some takeaways.

1. Sunlight helps kill the virus faster

President Trump looks at a chart April 23, 2020, at the White House on the effects of temperature, humidity and sunlight on the novel coronavirus. (Jonathan Ernst/Reuters)

This is based on a government-run, not peer-reviewed lab study of the virus suspended in particles of saliva.

Health officials and scientists suspected that the virus could die at a much faster pace with exposure to higher temperatures and humidity. But when you add sunlight to that, the half-life of the virus (how long it takes to become reduced in half) is minutes, vs. hours, this new study found.

That means outside in typical summer weather, the virus can die much more quickly, said William N. Bryan, the acting undersecretary for the science office in the Department of Homeland Security. The Washington Post’s Andrew Freedman and Jason Samenow report that this finding matched other laboratory studies.

Bryan warned that this does not mean that when summer comes, the virus will be gone. There are major outbreaks in warmer places, including New Orleans. But this could inform how governors reopen their states — for example, some playground equipment that is in direct sunlight on a warm day may not be as infected as other areas. “That doesn’t take away guidance to protect yourself,” he said. “This is just another tool in our tool belt, another weapon in that fight.” He gave no specific guidance for states to consider.

Trump reminded the audience that he guessed the virus could die when the weather gets warmer: “I once mentioned that maybe it does go with heat and light and people didn’t like that statement very much.”

(At a rally in February Trump said: “Looks like by April, you know, in theory, when it gets a little warmer, it miraculously goes away.”)

When The Post’s Philip Rucker asked Trump whether it was dangerous to present this finding now, possibly causing people think they’d be safer to go outside, and given that people are dying in Florida, Trump said: “I’m just here to present talent. I’m here to present ideas because we want ideas to get rid of this thing.”

“I hope people enjoy the sun, and if it has an impact that’s great,” he added.

2. The virus could be under control ‘by early summer’

But Vice President Pence, who spoke for the coronavirus task force with that prediction, couched it in careful language: As states reopen, they can’t let cases spike.

“If we continue these mitigation efforts in the days ahead, as states implement their policies, including phased reopening that will preserve those gains, we do believe by early summer we could be in a much better place as a nation, with much of this coronavirus epidemic behind us,” Pence said.

Trump said he may extend federal social distancing guidelines until then.

State leaders, county health officials and public health experts say that having widespread testing for the virus will be critical to opening up safely. One of Trump’s medical advisers on the virus, Anthony S. Fauci, said Thursday that “we’re just not there yet on that kind of testing to open economy. When asked about that on Thursday, Trump explicitly disagreed with him: “I don’t agree with them on that. No, I think we’re doing a great job in testing."

Trump also asserted that there is a national strategy to ramp up testing, which would be news to many governors who have said they feel as if they’re competing with other states to get tests without help from the federal government.

3. Trump seems open to letting states go bankrupt

The next big debate in coronavirus economic relief is whether to help states and localities, which are suffering from a lack of tax revenue. On Wednesday, Senate Majority Leader Mitch McConnell (R-Ky.) said he’d be okay letting states in trouble go bankrupt, prompting outrage from Democratic and Republican governors. McConnell’s office suggested approving something like this would be a “blue state bailout.”

But Trump seemed open to it, too, saying he’s talked to McConnell as well as the Democratic governors of New York, New Jersey and California about it. New York Gov. Andrew M. Cuomo had some strong feelings about it Thursday, saying: “This is really one of the dumb ideas of all time,” and that multiple states going bankrupt risks “a collapse of this national economy.”

Trump said he hadn’t made up his mind, but what he did say echoed McConnell’s sentiments: “Some states have not done well for many years, long before the virus came.” He added later: “It is interesting that the states that are in trouble do happen to be blue.”

Larry Hogan, the Republican governor of Maryland who chairs the National Governors Association, said earlier Thursday that a similar comment by McConnell was “complete nonsense.”