"This bacteria is different from what we are used to. Something has happened to it. We have to look into if it is how it enters the body or what toxins it produces that causes the severe symptoms," specialist Anders Wallenstein of the Swedish Institute for Communicable Disease Control (Smittskyddsinstitutet) said to news agency TT.
Usually it is children and the elderly that are affected the worst but this variation seems to hit otherwise healthy adults the hardest.
Sweden's health services and the Institute have received many calls from an increasingly worried public.
"So far, there is no reported case that hasn't been connected to Germany and therefore you can feel pretty safe not to fall ill from eating food in Sweden. However, this can change," Wallenstein said.
According to Wallenstein it is too soon to say when the source of the outbreak will be identified.
"It is detective work. First you have to have an indication where you should look and then scientists will have to identify the bacteria in the food. They may find it tomorrow, or in a few weeks, it is hard to say," Wallenstein told TT.
The bacteria combines a very poisonous toxin with something akin to an adhesive, which grabs hold in the intestines, allowing the bacteria to pump out poison.
The EHEC outbreak has cost 18 lives so far, one of which in Sweden.
But if the spread hasn't ceased it seems to have slowed down for the time being.
"We received 50 test results today, from travelers who've been in Germany and from their relatives. All the tests came back negative, so it looks favorable, and we will continue to take tests all weekend," Leif Dotevall, deputy epidemiologist in Gothenburg, said to TT.
"This tells us that the spread is decreasing, at least in our area," he continued.
The Russian decision to introduce an immediate ban on imports for vegetables from EU countries has turned out to be incompatible with World Trade Organization's entry rules.
Russia applied to join the WTO earlier this year, and the decision to stop buying vegetables does not sit well with this, reports news agency AFP, citing a spokesperson from EU.
The decision, made public on Thursday, was immediately met with sharp criticism from the EU and health commissioner John Dalli, who considered it to lack proportion.
On Friday, Russian prime minister Vladimir Putin said that he would look into the validity of the Russian stop on imports.
But he also added that he was not going to let Russians "be poisoned" for the sake of the WTO, according to news agency AFP.
Lebanon also announced a stop to the import of vegetables from the EU on Friday.
In Sweden, the condition of the three patients currently at Sahlgrenska hospital in Gothenburg continues to be serious but stable.
One of the two patients treated at Varberg's intensive care unit has improved, the other is stable.
The woman who is being treated at Jönköping's hospital, in the county of Småland, south of Stockholm, is still gravely ill, but her condition hasn't worsened.
So far, 46 people in Sweden have fallen ill with EHEC, of which 15 have developed the serious complication Hemolytic-uremic syndrome (HUS).