Billions of dollars have been wiped off the value of McDonald’s after the fast food giant was knocked by an E. coli outbreak which health authorities linked to its hamburgers.

Shares dropped by as much as 6% in morning trading on Wednesday, adding to a fall in its stock overnight.

Its market value has fallen to about 215 billion US dollars (£166 billion) from over 225 billion dollars (£174 billion) on Tuesday.

It came after the US Centres for Disease Control and Prevention (CDC) issued a food safety alert on Tuesday, reporting at least 49 illnesses across 10 states.

The outbreak, which was linked to McDonald’s quarter pounder burgers, resulted in one death while 10 others were hospitalised, according to the CDC.

McDonald’s stores in the UK and Ireland have not been affected.

The CDC said each individual who became ill and was interviewed reported eating at a McDonald’s before the illness started, with most specifically mentioning they had a quarter pounder.

It added that the specific ingredient linked to the illness has not yet been identified but that investigators have focused particularly on the slivered onions and beef patties in the hamburgers.

McDonald’s reported to the public health authorities that they proactively removed the slivered onions and beef patties used for the quarter pounder hamburgers from stores in the affected states while the investigation continues.

The quarter pounder product is, therefore, temporarily unavailable in some states.

On Wednesday morning, McDonald’s USA president, Joe Erlinger, told NBC: “We are very confident that you can go to McDonald’s and enjoy our classics.

“I want to say to our consumers that you can confidently go to McDonald’s today.

“We took swift action yesterday to remove the quarter pounder from our menu.

“If there has been contaminated product within our supply chain, it’s very likely worked itself through that supply chain already.”

McDonald’s has been contacted for comment.