(CNN) Bleach and sunlight can both kill the new coronavirus on surfaces outside the body, a federal official said Thursday at the daily White House briefing.

But that simple scientific summary quickly turned into a puzzling brainstorm by President Donald Trump about how to treat Covid-19 patients, from injecting disinfectants -- a dangerous prospect that could be fatal -- and possibly streaming light into the body.

Here's what was said -- and what science really tells us about safely killing viruses.

Bleach should not be injected or ingested

Studies of the virus have shown that bleach kills coronavirus on surfaces in about five minutes, and isopropyl alcohol destroys it on surfaces even faster, Bill Bryan, a senior official at the US Department of Homeland Security, told reporters Thursday.

Bryan, who is not a scientist, said a US Army biological lab outside Washington DC had been conducting tests on the virus.

Trump then said this: "And then I see the disinfectant where it knocks it out in one minute. Is there a way we can do something like that by injection inside or almost a cleaning ... it would be interesting to check that."

Chlorine bleach is toxic. It can and does kill people who drink it. The US Food and Drug Administration regularly warns the public against drinking bleach, or even inhaling fumes from bleach. It's also irritating to skin.

"As a global leader in health and hygiene products, we must be clear that under no circumstance should our disinfectant products be administered into the human body (through injection, ingestion or any other route)," Reckitt Benckiser said in a statement.

The US Centers for Disease Control and Prevention last week said calls about poisonings with cleaners and disinfectants had increased more than 20% in the first three months of 2020 -- as coronavirus cleaning increased -- than from the same period a year earlier. Among cleaners, bleaches accounted for the largest percentage increase in calls from 2019 to 2020.

The CDC recommends using soap and water or bleach to kill the virus on surfaces. Rubbing alcohol that's at least 70% alcohol will also kill it on surfaces; 60% for your hands.

Sunlight can kill the virus but isn't a cure

Tests also have shown the virus in droplets of saliva survives best indoors and in dry conditions, Bryan said.

"The virus dies the quickest in the presence of direct sunlight under these conditions," he said. "Our most striking observation to date is the powerful effect that solar light appears to have on killing the virus, both surfaces and in the air."

Temperature and humidity also affect how long the virus survives, he said.

Bryan called the finding "another weapon in the fight that we can add to it and in the summer." But he added: "It would be irresponsible for us to say that we feel the summer will totally kill the virus. We have an opportunity, though, to get ahead with what we know now and factor that into the decision-making."

Vice President Mike Pence called Bryan's presentation "encouraging news about the impact of that heat and sunlight have on the coronavirus, which will increase the confidence that we feel about the coming summer."

Then, Trump surmised: "Suppose that we hit the body with a tremendous, whether it's ultraviolet or just very powerful light and I think you said that it hasn't been checked and you're going to test it. Suppose you can bring the light inside the body."

It was not immediately clear how the President might propose delivering light into the body.

Ultraviolet light can damage skin and lead to cancer if people get enough of it.

As for how the summer might impact the virus, members of an influential National Academy of Sciences committee told the White House earlier this month that it doesn't look like the coronavirus will go away once the weather warms up.

"There is some evidence to suggest that (coronavirus) may transmit less efficiently in environments with higher ambient temperature and humidity; however, given the lack of host immunity globally, this reduction in transmission efficiency may not lead to a significant reduction in disease spread without the concomitant adoption of major public health interventions," the panel wrote, noting that the virus continued to spread in countries experiencing warm weather

Myths already have been debunked

Trump's statements echo myths and rumors that got so rampant on the internet and in social media that the World Health Organization posted a myth busters page to debunk them.

"No. Spraying alcohol or chlorine all over your body will not kill viruses that have already entered your body," the WHO's page states. "Spraying such substances can be harmful to clothes or mucous membranes (i.e. eyes, mouth).

"Be aware that both alcohol and chlorine can be useful to disinfect surfaces, but they need to be used under appropriate recommendations."

As for sunlight and heat, "exposing yourself to the sun or to temperatures higher than 25C (77F) degrees DOES NOT prevent the coronavirus disease," WHO says on its website. "You can catch COVID-19, no matter how sunny or hot the weather is. Countries with hot weather have reported cases of COVID-19."

It also warns against using ultraviolet lamps, including tanning lamps, to try to kill virus. "UV lamps should not be used to sterilize hands or other areas of skin as UV radiation can cause skin irritation," WHO cautions.