The patient was a 67-year-old male American Chinese. On the evening of August 28th, 2023 (US local time), the patient developed fever symptoms, with a maximum body temperature of 39.7 ℃. On August 29th (US local time), he visited the Massachusetts General Hospital of Harvard Medical School. Chest X-ray showed bilateral ground glass shadows, diagnosed with “pneumonia”, and was treated orally with “azithromycin, benzoate, amoxicillin, and guaiacol”. The patient arrived in Zhuhai on August 31st (Beijing time). On September 1st, he sought medical attention at the Fifth Affiliated Hospital of Sun Yat-sen University due to persistent fever symptoms. Admission examination: hemoglobin 93.00 g/L↓, eosinophils 0.00 × 10⁹/L↓, urinary occult blood 4 +↑, urinary protein 2 +↑. Microscopic examination of blood smear revealed the presence of Babesia microti in red blood cells. Metagenomic next-generation sequencing (mNGS) detection of 1 338 308 sequences of Babesia microti. The patient has been residing in New Hampshire, USA (Babesia epidemic area) for a long time, and had a history of insect bites. The next-generation sequencing results showed positive results for Babesia microti. The patient was treated with minocycline (0.1 g each time, once every 12 hours) + clindamycin (0.6 g each time, once every 6 hours) for anti-infection. After treatment, the condition improved, and the patient was discharged on September 11th. The blood count prior to discharge showed: hemoglobin 76.00 g/L, platelet count 208.00 × 10⁹/L, alanine aminotransferase 39.60 U/L, and aspartate aminotransferase 37.20 U/L. After 2 months of follow-up after discharge, the patient recovered well.