(CNN) -- One of the key aspects to gaining control of the fast-moving cholera outbreak in Haiti is the simplest of human necessities, actor and activist Sean Penn told CNN's "AC360°."
People must stop using contaminated water, he said, noting that they will only do that if clean water is provided.
"So, whether that's through filtration systems or trucked in water, this is going to be the essential element -- water, water, water," Penn said in an interview that aired Monday.
Penn, a co-founder of Haitian relief organization J/P HRO, visited Haiti over the weekend -- days after news broke about the cholera outbreak in the earthquake-ravaged country.
"It's bad," Penn said of the conditions in the Caribbean nation, devastated by a magnitude 7.0 earthquake on January 12 which killed nearly a quarter million people, left more than 1.6 million people homeless and destroyed homes, commercial buildings and basic infrastructure.
And the cholera outbreak has made a bad situation worse, he said.
"What we know about it at this point is that it is affecting a very regional area, in particular the epicenter of it, but it's spreading very fast," he said.
Penn also told CNN's Anderson Cooper that he was concerned about whether there were enough medical supplies and personnel available in Haiti to treat those infected by the fast-moving outbreak.
Reaching patients with medication and treatment within a specific time frame is of the utmost importance, he said, and medical supplies could be caught up in bureaucratic processing at warehouses.
"Now we have this terrible epidemic, and if it hits camps... we're going to have a devastation that nobody wants to see," he said.
The actor's relief organization runs one of the many camps sheltering Haitians until more permanent housing is available, and Penn said his camp is preparing to treat patients with cholera if that becomes necessary.
"We're stockpiling [supplies] now, but it's slow, and our access has been disappointing to those supplies in country. We have those things that we're initiating ourselves, and with support, we'll be able to do a lot more," he said.
With the help of Oxfam, J/P HRO's camp has chlorinated water, Penn said.
"While it's not pleasant to drink, it's safe to drink and to wash with and to wash fruits and vegetables with. There are many, many camps that don't have those services," he said.
In the interview, Penn also weighed in on the slow pace of the recovery effort in Haiti, one of the poorest nations in the Western Hemisphere.
To get people out of camps in Port-au-Prince, he said, 400,000 temporary shelters must be built, he said.
So far, 17,000 have been constructed, according to U.S. Agency for International Development.
"The camps are a devastation. We have probably the best-organized camp, and it's a terrible place to live. It doesn't provide dignity, pride, health, security on any human reasonable level. And yet, this is where they're going to be for some time," he said. "I don't want to make predictions on how long it's going to be. Our job is to work every day to give them other options. But it's going to be a long time."
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