Video: the aftermath | Eyewitness report | DEC appeal

Teams of aid experts allowed into the cyclone-ravaged Irrawady delta have returned to Thailand with the bleakest of warnings: Burma is on the brink of a “devastating public health crisis” compounded by an emerging refugee disaster.

But for the hundreds of aid workers who have flown into Bangkok from around the world, the chances of a sudden glut of the precious entry visas appeared slimmer by the hour.

Rumours have begun circulating between international aid organisations that the Burmese regime is preparing to close its doors altogether: a decision, warned UN-affiliated aid workers, that will cost the lives of thousands.

Although some medical and food supplies have begun to trickle into the country – a cargo plane chartered by the International Committee of the Red Cross carrying 35 tons of aid was one of the latest to land – disaster experts said that the shipments fell far short of what was needed.

Stephan Goetghebuer, a director of operations at Medecins Sans Frontieres said that while the Burmese authorities had allowed just enough leeway for a few aid shipments “it's no more than a drip-feed, really, given a serious response is more than required.”

Dysentery, diarrhoea and other diseases would, said medical observers, tear through the storm’s survivors as they struggle to rebuild their lives.

Warehouses full of unsent medical and food supplies are a rising source of fury among aid groups. But the lack of expertise on the ground is also significantly heightening the crisis – the junta’s stonewall tactics against foreign aid distributors means that many of the world’s foremost specialists in disasters are pacing around their offices in Bangkok just a few hundred miles from where they believe they should be.

The frustrated aid workers are not the only ones waiting in Thailand with rising dread for the situation there and growing rage with the behaviour of the Burmese authorities.

Khin, who works as a gardener in Bangkok, is one of the hundreds of thousands of Burmese living in Thailand with family back home – family that he has not heard from and now believes have been claimed by the cyclone. Over the weekend, large numbers of Burmese migrants protested outside their own embassy in Bangkok, demanding that the regime abandon its objection to foreign aid.

Holding a page of newspaper bearing aerial photographs of the devastation, Khin weeps as he thinks of his sister and her family: “it is terrible not to know, but it is worst to think that they might have been saved if the foreign aid had been allowed in.”

So far, only a few of the assessment teams that would normally be on the scene to establish the scale of the problem have been allowed into Burma to do their jobs.

For the logisticians, doctors, water specialists and other aid workers, the teams now returning are expected to deliver an extremely grim picture of what is needed to ensure the survival of an estimated 1.5 million people affected by the cyclone.

After three days probing the worst-affected parts of the country, returning assessment teams said that the Burmese junta’s de facto blockade on large-scale foreign assistance is now in danger of creating a separate refugee crisis.

Tens of thousands of people left homeless by Cyclone Nargis have, until now, stayed put and held out in the desperate hope that food, shelter and medical supplies would come to them eventually. But because more than a week has now past and nothing has arrived, many have set off in search of salvation.

One of the teams sent by the aid group WorldVision said it discovered 30,000 such refugees encamped around the village of Myaung mya. “These are desperate people who, after a week of waiting, are giving up on the aid response and heading off in search of food and shelter," said Chris Webster, one of dozens of WorldVision workers effectively trapped in Bangkok waiting for Burmese visas.

Aid workers who have flown into Bangkok from around the world said that the weekend had been a crucible of frustration and anger with the Burmese regime. Emotions have swung wildly between hope and despair as the odd visa application has been processed, only for hundreds of others to sink without a trace.

This morning optimism was triggered by news that the former prime minister of Thailand, Surayud Chulanont, was planning to lead a delegation to Naypyidaw in a last-ditch bid to persuade the junta to open its borders to large-scale foreign assistance.

But by those hopes faded as the junta re-iterated its position that only the Burmese government would be allowed to distribute whatever aid was sent in.

Times Recommends

• No apology for Germany’s own Nazi victims
• Intricate web of fear and hope tying down deal
• Victims remembered a year after Mumbai attacks