Cucumbers in clear – so what is causing deadly E.coli outbreak?

After days of recriminations that threatened new inter-European trade wars, the German authorities conceded last night that contaminated Spanish cucumbers are not, after all, to blame for a mystery illness which has claimed the lives of 16 people and infected more than 1,200 others.

It has now emerged that many more women than men are falling ill in what is now one of the world's most deadly E.coli outbreaks. The search to find the source of the infection was stepped up, although scientists said that vegetables such as spinach or salads remained a likely cause because of animal manure used as fertiliser.

Russia meanwhile threatened to extend its ban on German and Spanish produce to include the whole of the European Union, as growers demanded hundreds of millions of euros to compensate them for the collapse of cucumber, tomato and lettuce sales.

The German State Agriculture Secretary Robert Kloos admitted that tests revealed that Spanish cucumbers did not carry the deadly bacteria strain – confirming earlier investigations carried out on three sites in Spain. "Germany recognises that the Spanish cucumbers are not the cause," he told reporters at an EU farm ministers meeting in Hungary.

The Spanish Agriculture Minister Rosa Aguilar criticised the German response: "Germany accused Spain of being responsible for the E.coli contamination in Germany, and it did it with no proof, causing irreparable damage to the Spanish production sector." Her Andalusian counterpart, Clara Aguilera, appeared on television to eat a cucumber, in the hope of convincing the continent that they were safe.

Denmark, the Czech Republic, Luxembourg, Hungary, Sweden and Belgium have stopped importing Spanish produce while Germany itself has told consumers to stop eating it.

The French Health Minister Xavier Bertrand also condemned the handling of the crisis. "I want to know the origin [of the contamination]. We need completely transparent information from the German authorities, and from the Spanish authorities as well," he said.

The European Commission said it was doing everything it could to find the source of the outbreak but that, despite the mounting death toll, a ban on any product remained "disproportionate". Britain's Health Protection Agency said there was no evidence to suggest any infected products had reached the UK but advised consumers to wash and peel salad and fruit before eating it. So far three people in the UK have been infected, all of them Germans.

Experts remained puzzled as to why the bacteria continue to affect more women than men. One theory is that women are more health-conscious and likely to eat salad. Professor Ulf Goebel of the Institute of Microbiology at the Charité Hospital, Berlin, said: "At present [it is affecting] mostly adult people: young adults and women are severely affected. The reason for this is still unknown."

The disease has been identified as hemolytic-uremic syndrome, a serious complication of a type of E.coli known as shiga toxin-producing E.coli which affects the blood, nervous system and causes kidney failure. Other victims, all of whom had returned from Germany, have also been confirmed in Spain, Denmark, France, Netherlands, the Czech Republic and Sweden, where a woman died of the disease yesterday.

Spanish farmers are dismayed at being blamed for the outbreak. As orders have been cancelled, growers are laying off workers at a time when the country is battling with 21 per cent unemployment. "We farmers are furious, very angry and indignant because we see no explanation for us to be treated this way on the basis of unfounded information," said Francisco Vargas, a farm leader in Almeria where two companies are being investigated.

British farmers are concerned that a glut of unwanted cucumbers could lead to a collapse in price for UK growers. Derek Hargreaves, of the Cucumber Growers' Association, said there are around 60 producers currently growing the salad vegetable. He said the source of contamination was most likely during processing in Germany.

When E.Coli turns deadly

E.Coli are bacteria that occur naturally in the intestines of humans and all warm-blooded animals. Most strains are harmless but some, such as the O104 strain implicated in the German outbreak, produce toxins that can cause serious illness.

Cattle can carry these toxin-producing strains of E.coli in their intestines without showing any symptoms of illness. If their manure is then used as a fertiliser there is a risk that vegetables such as cucumbers may become contaminated. These type of E.coli survive in harsher conditions than ordinary E.coli and so are likely to be more persistent in the environment. Infection can be avoided by properly washing vegetables.

Timeline: How a lethal bug created a Europe-wide food panic

21 May An 83-year-old woman dies in Lower Saxony, Germany, after being ill for a week. She is later found to have been infected with E.coli.

24 May After two more deaths, Germany's national disease control and prevention agency, the Robert Koch Institute, says the infection rate is "scarily high".

25 May 80 people are confirmed to have become "seriously ill" from illness caused by E.coli.

26 May Spanish cucumbers are implicated by German medical officials, who say three out of four contaminated specimens came from there. The German authorities advise their citizens to avoid eating cucumbers, tomatoes and lettuces, while some products are removed from sale. In the UK, the Health Protection Agency warns British travellers to Germany.

28 May The number of deaths in Germany suspected to have been caused by the virus rises to 10, as the European Centre for Disease Prevention and Control, which monitors disease in the European Union, says the outbreak is one of the largest of its kind seen anywhere in the world.

31 May As the fatalities spread across borders to Sweden, adding to the 15 deaths in Germany, Spain's Agriculture Minister claims that her country's produce has been blamed "without having reliable data". The number of people infected in Europe has now passed 1,200.

A history of food scares around the world

Britain British beef was banned in the European Union for 10 years following a massive outbreak of BSE, or mad cow disease. The ban lasted until 2006 and resulted in estimated losses of £675m a year for British farms.

Japan Following the devastating earthquake and tsunami earlier this year and the ensuing nuclear crisis, many countries stopped importing Japanese produce, such as fish and dairy products. The food was feared to be contaminated by radiation from the Fukushima nuclear power plant which was destroyed in the disaster.

Thailand The European Union followed Japan in 2004, as it banned all poultry sourced from Thailand amid fears that avian flu could transmit from the birds to humans. The attempt to halt the spread followed several confirmed cases and one death in the country.

Taiwan Taiwanese sports drinks were banned in Hong Kong this week, after the chemical plasticiser, DEHP, was found. The chemical can affect hormone balances in young people, and extended consumption can lead to liver damage, kidney problems and cancer. The owner of the drinks company using the chemical has been arrested by Taiwanese authorities.

Ireland The EU announced a recall of all Irish pork products in December 2008. Tested meat was found to be contaminated with dangerous levels of carcinogenic dioxins, thought to have come from tainted animal feed. Thousands of jobs were lost in the Irish pig processing industry and farmers demanded compensation following the mass recall.

China Restrictions were imposed in the US and Europe following the deaths of six babies caused by the industrial chemical melamine contained in Chinese baby milk in 2008. More than 300,000 children were taken ill during the scare, causing widespread panic across Asia. Those considered responsible for the crisis were arrested and prosecuted by Chinese authorities.