The bacteria neoehrlichia can be difficult to detect, however.
"Routine analysis don't help discover the bacteria, as it can't be cultivated, "Sahlgrenska Academy researcher Christine Wennerås said in a statement on Monday.
She said that a person older than fifty and already suffering a blood disease or rheumatic condition was most at risk, as neoehrlichia can lead to blood clots in the legs and in the blood vessels in the head. Patients receiving cortisone treatments were also considered at risk.
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Of the 19 known cases worldwide, six patients were diagnosed in Sweden.