You might have to stay away from low-lying areas for as long as twenty hours after the first warning.

VOA: special.2011.06.07

In hindsight the low ratios were warning flares.

FORBES: Beyond Low Price-Earnings Ratios

He opened the coop and stuck his hand in toward the fierce creature inside, eyes yellow, beak sharp as a cat's claw, trilling a warning so low it was almost a growl.

NPR: Excerpt: 'The Prince of Frogtown'

The British Medical Association has dismissed this, arguing they had been warning stocks were running low for weeks and claiming not all of the doses may have gone to GPs - pharmacists and primary care trusts also stock the vaccine.

BBC: NEWS | Health | Q&A: Flu jabs