Recently in a few European countries a new pathogen transmitted by ticks Ixodes ricinus - Candidatus Neoehrlichia mikurensis was identified. It is a Gram negative intracellular bacterium belonging to the Anaplasmataceae family. Worldwide 23 cases were described, among which 16 in Europe. Infection with Candidatus Neoehrlichia mikurensis in humans runs mainly with fever, headache, nausea, arthralgia, thrombotic or haemorrhagic lesions, subcutaneous haemorrhages, haemorrhagic rash, general malaise, weight loss. The course of infection may be acute or chronic. The diagnosis is based on TaqMan real-time PCR, which allows for the detection of the gene coding for 16S rRNA and a blood smear. The drug of choice is doxycycline. Due to the fact that the Ixodes ricinus ticks are common in Poland, there is a probability of infection with Candidatus Neoehrlichia mikurensis among patients bitten by ticks. The possibility of non-symptomatic human infection Candidatus Neoehrlichia mikurensis in north-eastern Poland was shown, confirming the necessity to conduct research on a larger scale. Moreover, awareness of physicians about the possibility of infection in patients with non-specific symptoms after tick bite should be increased.