Illness means both Greece's new prime minister and finance minister will miss an anxiously awaited summit of European leaders this week.
It also means a visit by the country's international lenders has been delayed.
The news was a blow to Athens' attempts to ease the terms of its bailout in the teeth of German opposition, as well as an untimely complication for a summit that some hoped would take new steps to grapple with the region's debt crisis.
According to a document prepared for the June 28-29 meeting, European leaders will discuss specific steps towards a cross-border banking union, closer fiscal integration and the possibility of a debt redemption fund.
But Prime Minister Antonis Samaras underwent eye surgery on Saturday and Vassilis Rapanos is in hospital after suffering from nausea before he could be sworn in as finance minister.
Instead, Greece's foreign minister and outgoing finance minister will attend the meeting to ask for the terms of the €130 billion ($207 billion) bailout to be loosened.
The unexpected turn of events forced the postponement of a visit to Athens later today by officials from Greece's "troika" of lenders - the European Union, European Central Bank and International Monetary Fund.
Athens faces a stern test at the two-day EU summit, with euro zone paymaster Germany particularly resistant to giving Athens any leeway.
German Finance Minister Wolfgang Schaeuble made his country's position all too clear in a bluntly worded interview on Sunday, telling Greece to stop asking for more help and instead move quickly to enact reform measures already agreed.
"The most important task facing new prime minister Samaras is to enact the programme agreed upon quickly and without further delay instead of asking how much more others can do for Greece," Schaeuble, a close ally of Chancellor Angela Merkel, told Bild am Sonntag.
His comments came as the paper carried a poll of 4,000 people showing 78 percent of Germans and 65 percent of French people wanted Greece to leave the euro zone, with 51 percent in Spain and 49 percent in Italy also backing a Greek exit.
YET ANOTHER SUMMIT
Having once hoped this week's summit could be a turning point for the EU debt crisis, financial markets have toned down expectations of concrete progress.
"We believe it will conclude with further general support for the development of a roadmap towards tighter fiscal union, but with significant preconditions attached to various stages of the timeline," said analysts at Barclays.
"We doubt that concerns about the method for the pooling of national sovereignty can be sufficiently resolved in detail, implying there will be further deliberations during the second half of the year."
The lack of excitement was palpable in the currency market, where the euro was pinned at US$1.2530 in Asian trade on Monday, just a whisker above its lows of last week.
Analysts do expect some sort of growth pact to emerge from the summit, though the touted spending of 130 billion euros is modest at best.
There is likely to be heated discussion on issues such as debt mutualisation and any pooling of liability under a banking union, with Germany adamant that it will not be put on the line to underwrite the liabilities of other euro zone countries.
No major decisions are expected at the summit and a definitive solution seems a long way off.
European Council President Herman Van Rompuy hopes to have a more thorough set of plans drawn up by the next EU leaders' summit in October, or possibly the one after in December.
Key also will be the attitude of the European Central Bank (ECB) which has fiercely resisted calls to become a lender of last resort and help ease funding pressures in the region.
It took a small supportive step on Friday, relaxing its collateral rules to let financial institutions pledge a wider range of assets in exchange for cash. The move helps counter the impact of credit rating downgrades.