There are 11 people in the UK with food poisoning apparently linked to a toxic E.coli outbreak, the Health Protection Agency said.
Eight have bloody diarrhoea and three are being treated for haemolytic uraemic syndrome (HUS) - a deadly complication of E.coli.
All are from or have visited northern Germany, where experts are working to try to find the source of the outbreak.
Globally more than 1,800 people have been infected so far, and 18 people have died. Around one in three of those affected have been hit by HUS, a complication that affects the blood, kidneys and, in severe cases, the central nervous system.
The number of HUS cases in Germany has risen to 520 and 1,213 cases of bloody diarrhoea linked to the outbreak have been reported so far.
Experts there said on Friday there were signs that the infection could be slowing, but have warned more cases will arise.
The outbreak is thought to be the deadliest in recent world history, and is one of the biggest. In 1996, 12 people died during a Japanese outbreak, while seven died in a Canadian outbreak in 2000.
Scientists believe salad vegetables and leaves may be to blame for the latest outbreak, although the World Health Organisation (WHO) says the origin "of the outbreak still remains unknown".
The bug has now been identified in people in the Czech Republic, France and the United States, as well as Germany, Austria, Denmark, the Netherlands, Spain, Sweden, Switzerland and the UK.
On Friday night, experts from WHO said the strain of E.coli was extremely rare and, although seen in humans previously, it has never been at the centre of an outbreak. The strain is known to be resistant to many antibiotics, making treatment difficult.