Accident and emergency units in West London were under severe pressure on Sunday evening trying to cope with thousands of people laughing uncontrollably.
Said a spokesman for the Welsea and Chestminster: "We are working flat out and staff have been called in from holiday in an effort to cope with the outbreak.
"It began at about 5.45 this afternoon when a man was brought in struggling to breathe, holding his sides and laughing.
"More cases followed very quickly until we had to open extra rooms and wards to take the extra case load."
The picture was repeated across West London and reports are suggesting that it is also the story across the country.
The epidemic seems to have been caused by an incident during the "massive" Premier League football match between Tottenham Hotspur and Chelsea. With the score at 1-1, Chelsea had the chance to grab a win when they were awarded a penalty with minutes left to play.
But star striker, Didier Drogba, who started the game on the substitutes' bench, made a feeble effort, easily kept out by Spurs' keeper Gomes.
Mrs Pentheselia Roast, of Holland Park, said: "I heard my husband start to laugh while he was watching the football. He couldn't seem to stop and appeared to be in some distress so I called an ambulance.
"I couldn't make out all he was saying, but some of it was 'haha... Drogba... wanker...'"