Seventy years after The Grapes of Wrath, Chris McGreal recreates John Steinbeck's famous fictional journey to reveal life in the worst economic crisis since the Great Depression

Looking back on the past few weeks, Johnnie Levy can see how she was driven to the brink of death and didn't care.

The sharpest economic downturn of her 63 years stripped Levy of her beloved job as a seamstress and unravelled her world until she found herself sitting in a church hall in the black end of Tulsa waiting to see a nurse with a syringe in one hand and a Bible in the other.

Tulsa has seen its share of poverty and desperation over the years. In the 1930s, it saw a tide of hundreds of thousands struggling west along Route 66 to escape economic collapse in the north and the notorious dustbowl of drought and wind across the Midwest. Whether they had lost their land or their jobs, that flow of desperate humanity – chronicled so devastatingly through the fictional Joad family in John Steinbeck's Grapes of Wrath – struggled hard to find enough to feed and clothe their children as they trekked towards an illusory dream of prosperity in distant California.

To travel the old road today – stumbling across crumbling ghost towns and half-abandoned communities, across the sprawling Native American desert reservations, through cities where people work all the hours they aren't sleeping and still cannot afford to go to the doctor - is to encounter new despair, some of it still recognisable to the Joads.

The banks are once again evicting. Foreclosures plague the parts of northern Arizona and New Mexico traversed by the evicted 70 years ago.

But the monster – as Steinbeck described the financial system – has spawned modern beasts unknown to the Joads, such as the vast multinationals discarding American workers in favour of cheaper labour in Mexico and the health insurance companies that cut off the medical lifelines to the gravely ill.

For those who fall off the juggernaut of American capitalism, or who fail to find space on it in the first place, there are considerable challenges in a land with an inherent suspicion of people in need.

There were a dozen or more at Tulsa's Friendship Baptist Church – a young blonde mother grappling with two small children, an old Mexican immigrant with a gammy leg and a walking stick, elderly African American women – staring at a television with an animated preacher beseeching them to follow the word of God. Occasionally someone stood and made their way out the rear of the hall to a room where they were encouraged to pray for divine intervention.

But it was the other door, at the front of the church, that everyone had half an eye on. Periodically a name was called to a large van in the car park painted with an orange cross that formed the "T" in the logo Good Samaritan. Inside doctors and nurses – all required to be good Christians – offered free consultations and medicines to those who Oklahoma's hospitals don't want to see because they can't pay.

The van perpetually makes the rounds of Tulsa's churches in run-down neighbourhoods, providing for the city's working poor, struggling pensioners and, increasingly, newly unemployed Americans when their health becomes one more burden on top of the daily trial to pay the rent and put food on the table.

"It affected me very emotionally when I lost my job," said Levy, who shares a first name with her father. "I'm a seamstress and I love to sew and I love to talk to people about sewing. That's one of the reasons I stopped taking the medications. I got to the point where I didn't care, and that's not right."

Levy was cut adrift when the recession first reduced her hours and then wiped out her job in June. With the job went the medical insurance that paid the cost of the daily dose of insulin she needs to counter diabetes and for other treatments that come with age.

Although Levy has a pension, most of it is eaten up by rent on a one-bedroom flat and food and utilities. She shakes her head at her confused priorities but said there simply wasn't enough money left to meet the high cost of medicines and so, as she is still too young to qualify for the government's free medical care for the elderly, Levy stopped taking her insulin and other drugs.

"I didn't realise how badly it hit me and affected my health until I came here for treatment a couple of weeks ago. My blood sugar level was more than four times what it should be," she said. "I really have nothing else to lean back on."

Like so many in Oklahoma and across the south, Levy has a visceral distrust of government – not just President Barack Obama's administration but any of them.

In the heart of the Bible Belt it is often religious organisations that step in to the breach. Evangelising courses through Oklahoma and charity healthcare comes with God thrown in.

The Good Samaritan clinic sits in the car park of a church in a mostly black, with some Hispanics, district of Tulsa. The city, like so many in America, remains racially divided with much of its African American population, poor or affluent, gathered in northern neighbourhoods separated from the shiny, soulless heart of Tulsa and its pristine riverside walks by an industrial area and railway tracks.

"You see a lot of children in need here," said Veronica Banks, the minister at Friendship church. "You see a lot of elderly in need, a lot of single mothers and a lot of the working poor. Even though they're working they cannot afford medical care, the cost of healthcare the way it is. They're on minimum wage jobs or only working part time. We know the faces, we know the names."

Friendship church has a mostly black congregation. But the clinic draws white faces across boundaries that many in the city would not normally cross.

Among them is Harmony Banes, raised in poverty in what she describes as an abusive family without love by a mother who was eventually certified as clinically insane because of drug addiction.

"When I was in high school my family only had 60 bucks a month for groceries for five people. We lived in a trailer. I'm much happier here. I live in an apartment, around a lot of love," she said.

Banes is 27 and a mother herself now. Her husband pulls in about £15,000 a year as a bartender. From that there's the rent, two young mouths to feed and clothe, and the interest on college loans to study at Oral Roberts university in Tulsa, led by a prominent Christian evangelist and described as one of the "buckles on the Bible Belt".

She cannot even begin to think about paying back the principal on the loans. That leaves nothing for medical insurance for Baines or her husband, although the children get free cover from the state of Oklahoma. So she's at the free clinic to get blood tests.

"I pretty much hold back from going to the doctor," she said. "I was raised in a very poor family and never had insurance all the way through high school so for me it's normal. Thank God I've never been really super sick. If ever I needed something somehow it was provided.

God willing, whatever way it came, it came. It was just one of those faith, trust in God kind of things. If the needs not met there's a reason, I guess."

But Banes does worry and her lip quivers as she thinks about what would happen to her children if she ever did get really sick.

Banks says that as the financial crisis has deepened the free clinics are seeing more people like Banes.

"Everybody feels that economic crunch now. Generally in the past it was very rare we had to turn people away. But within the last eight months we've had to send them down the pipe to the next clinic because of the overflow. I walked in today and there was probably one of the largest lines I've seen at this clinic, and our clinic is a small clinic."

The patients are encouraged to pray while awaiting treatment. The medical staff introduce God as part of what the organisation describes as holistic care.

"We find a lot of people who come to us with a medical need but wouldn't set foot in the door of a church," said the mobile clinic's nurse, Lynn Hersey. "They want to check and see if someone who is a Christian can be trusted with one little thing, if they're going to shove Jesus down their throat because they ate the bait and came in through the door."

But there's another kind of evangelising at work too, involving a web of interests more focussed on Mammon than the Almighty. Much of Good Samaritan's work is funded by hospitals trying to keep patients who cannot pay out of emergency rooms, where they must be treated for any immediate health crisis by law whether they can pay or not. Those same hospitals have an interest in promoting charity as an alternative to President Obama's plans for government to take the lead in getting healthcare to the poor and the middle classes likely to be bankrupted by catastrophic illness.

Good Samaritan makes no secret of where it stands on the issue; the government has no business involving itself in healthcare.

"Governments treat you like a number," said the organisation's director, Dr John Crouch. "I really believe that there has to be a way to cover the folks who can't get care at all, and I think one of the ways is what we're doing. Maybe there's a different way of funding us, besides just funding us through our donations. We're emphasising that the more all the time."

Hersey concedes that the present system can be a tragedy for the poor.

What happens to someone with a chronic disease and no insurance? A woman with cancer, say, who might get the surgery she needs thanks to Good Samaritan but not the medicines afterwards. Hersey hesitates.

"They go without," she said.

You mean they die?

"Yes."

But Hersey quickly added that where there is no chemotherapy there is still God.

"I can say that even with the spiritual help they may die but for those of us who are Christians and believe in God intervening directly in peoples lives, we've seen many answers to prayer where medicine falls short. We have seen cancer turn around," she said.

It's a message Banes and Levy are only to open to. There is no anger or bitterness on their part at their situation, only a sense of helplessness and suspicion of authority.

Banes might have been expected to support Obama as the president most likely to act to help the poor.

"I voted for the other guy. McCain," she said. "Something grated against me [about Obama]. I really don't know what it was. I'm not racist. It's just one of those things where he's a good speaker, he talks very very well, even better than Bill Clinton I would say. But I wasn't about to go there. I went the other way."

Banes said she doesn't have confidence in the government to look after her interests even if the state of Oklahoma is providing free healthcare to her children.

"If for some reason Oklahoma state's healthcare failed then I would have something to worry about because of my children, I know. But I'm really not going to worry about it because that's one more thing to put on the plate. I don't really trust the government," she said. "The Lord has a plan and if anything happens, then it's meant to be".

Levy, too, voted for McCain.

"There's a lot of people with health problems who really need help and they have no place to turn," she said. "But the government? People who run government don't care about people like us. And there's a lot of people need to know that there's someone who cares about them."