FINDING an Australian footballer in a bar is no surprise. Finding him in one on a highway in rural Mozambique, drinking local beer with truck drivers and the sex workers they have pulled over to visit, is another story.

On a fact-finding mission in his off-season role as an ambassador for Melbourne's Burnet Institute — which works in disease prevention with some of the most impoverished communities in the world — Collingwood defender Harry O'Brien found himself in trickier positions than anything he's experienced in the back line.

Not least of them was the visit to an outdoor bar on a hot night in Chimoio, about an hour's drive from the Zimbabwean border. He watched astonished as smokers rolled their tobacco in $50 billion Zimbabwean notes. That country's trashed economy means they are good for little else.

O'Brien's visit to the bar was with a group of women who do outreach work in the places where sex is sold for survival, trying to educate men, and the women they pay, to be safe. Ostensibly with them as an observer, O'Brien proved a willing recruit to the cause, enlisting his fluent Portuguese to spread the message.

After introductions and some preliminary explanation of the rudiments of Australian football, he was grilled by a couple of drinkers, several beers into their evening, about the HIV infection rate in Australia. He told them that it is less than 1%, which roused more consternation than the foreign football code. In Mozambique, United Nations estimates put it at 16%, but among the 100 or so clientele in the bar this night, who can guess?

How is it that it is so low, the men want to know. This is not the time or place to give a lesson on the infection patterns and history of the disease in Australia, so Harry keeps it simple (if not entirely accurate). "By using condoms," he insists. It was plainly not the answer the men wanted to hear.

Over the week of his sabbatical, Brazilian-born O'Brien's hope was to gain some understanding of the African heritage bequeathed to him on his father's side, as well as to experience the reality of the development work he has lent his voice and support to.

He'd spent as much time as he could through the past season learning about the medical, cultural and social conditions that feed the spread of diseases such as HIV and malaria, and the factors that undermine the health of mother's and babies.

But none of it could prepare him for the many and varied encounters of his Mozambique itinerary. Like the one with a spiritual healer (whose prescription for pretty much everything was to have sex) and a woman said to be possessed by the devil — both performing within the too-close quarters of a thatched mud hut. A somewhat spooked O'Brien couldn't get out fast enough.

Then there were the children. The dancers who delighted with their fevered energy; the drummers whom he'd join, trading Brazilian and Mozambican rhythms; and AIDS orphans, whose physical neglect and utter aloneness broke his heart.

Reflecting on the week as his visit drew to an end, O'Brien says the thing that will stay with him most strongly will be those orphans. And the phrase that followed him down every street, waited on the car at every corner, punctuated every meeting: "Eu estou com fame" ("I'm hungry").

"You look in their eyes and you see the desperation. With the orphans, it was like their souls had been taken from them, they were just existing."

On a subsequent visit to an orphanage where some children had found refuge and kind care, he saw spirits still intact. "There were people with hope there, they were so positive, they are the ones that survive, like in any life situation. That's the solution, that is the only thing that will cure them," he says — more powerful than any medicine is having hope.

He ponders the question of what role a successful sportsman might play in the realm of development and aid. "I think when you have a sphere of influence, you can use it in various ways, I think you can use it very positively to capture the power of people as a collective — that has more power than any sportsperson or celebrity."

He compares this to people who are election-time donkey voters, or those who leave it to others to donate whenever there is a human crisis. "There is a collective consequence of all that."

Though a long way from the financial meltdown consuming the world, snippets of that reality have reached Mozambique: Obama fever, market failures, climate action. "It seems we're at an important stage in history, I think we are on the brink of a new world. I want to be part of that. I feel so optimistic despite what I've seen."

Has the experience changed him? "No. But it has strengthened my ideas. There's been so much positivity, and I want to feed off that energy."

Leaving Mozambique, two airport security guards delay him.

They want to admire his singlet, which pays homage to Bob Marley.

He was, they tell O'Brien, a man who claimed his roots and used his voice to speak up for Africa.