The UN estimates that in the first quarter of 2009 more than five million people, or nearly half Zimbabwe's population, will require food assistance, and shortages of basic foods are forcing people to buy in neighbouring countries.
Thousands of buses and private vehicles depart daily from various centres in Zimbabwe on shopping trips to South Africa, Botswana, Namibia, Mozambique, Zambia, Lesotho, Swaziland and Malawi to buy basic commodities for consumption or resale.
An IRIN correspondent travelled from the Zimbabwean capital, Harare, to South Africa's economic hub, Johannesburg, and boarded a battered bus in time to hear the conductor asking a passenger to offer prayers for a safe journey and an end to Zimbabwe's political crisis.
"We pray that our political leaders do not become selfish during the ongoing power-sharing talks, and that they should put the welfare of ordinary people first," said the passenger leading the prayers.
On 15 September rival Zimbabwean political parties signed a power-sharing deal, but the talks soon deadlocked over the allocation of cabinet posts.
The point of departure in Harare, known as Roadport, is frequented by illegal currency dealers and criminals waiting for passengers returning from their cross-border shopping trips.
The outward-bound passengers on the nearly 2,500km round trip to Johannesburg carry an array of empty bags that will be bulging with goods unavailable in Zimbabwe on the return journey.
The shortages are reflected in the passengers' food for the trip; a few people nibble on snacks and at a stop in Masvingo, 300km south of Harare, no one buys refreshments, even though the bus crew are given a free lunch if they bring in customers.
At Beitbridge, the border crossing between Zimbabwe and South Africa, the passengers are goaded and taunted by South African immigration officials.
"Go back to your [President Robert] Mugabe and tell him to retire from power. He has been in power for too long and is a disgrace to Southern Africa. Now you are coming to South Africa to loot all our food because you cannot deal with your dictator," one immigration official said.
After a few hours spent clearing immigration, the bus stops at the South African border town of Musina and the passengers stampede to the nearest supermarkets.
Thick wads of South African rands are brandished, the proceeds from informal trade or remittances to family and friends from the more than three million Zimbabweans thought to have left the country - where the unemployment rate has topped 80 percent in recent years - in search of work.
Meat pies, bread, sweets, biscuits and juices fly off the shelves as the parched and hungry travellers rush to buy rare items unavailable at home.
Shopping begins in earnest at Johannesburg's Park Station, and the once-empty bags are bulging when the passengers return to the terminus. When the bus trailer is full, bags, boxes and assorted other containers are squeezed into every available space on the bus and along the corridor.
According to the Reserve Bank of Zimbabwe, cross-border shoppers and traders are spending nearly US1 billion annually on groceries and household necessities in neighbouring countries.
The returning bus looks like a mobile supermarket selling everything from medicines, eggs, vegetables, meat, butter, sweets, rice and maize-meal - the staple food - to blankets, fridges, stoves, motor spare parts and stationery.
At the final stop before re-entering Zimbabwe there is one last buying spree, as the passengers realise they are returning to a country that is now characterised by empty shop shelves and a sense of panic sets in.
One of the passengers, Immaculate Gushu, told IRIN she had spent more than a month in the Lesotho capital of Maseru, where she sold an assortment of Zimbabwean goods, such as crotchet ware and wood carvings, and had used the profits to buy groceries for her family. "I am a single parent and economic hardships have forced me to engage in this kind of work," she said.
Memory Shumba, a 70-year-old grandmother, said she was forced to engage in cross-border trade because all her children had died from AIDS-related illnesses. "I sell commodities in South Africa, and sometimes I have problems getting my money from some of the clients who refuse to pay. I look after 14 orphans, as my children and their spouses have died of 'today's disease' [HIV/AIDS]. If I don't work hard, they will all starve to death."
Those who have been trading in South Africa for longer periods are curious to know about developments in their home country. "Is it true that there is yet another currency [denomination] in circulation? Have the political parties agreed on a way forward? Have shops started selling seed and fertiliser?"
On arrival at the Harare bus depot, the passengers are met with unconcealed joy by friends and relatives eager to know if their favourite foods have been bought.