Human T-lymphotropic virus

A 42-year-old Jamaican man comes to the office because of third upper respiratory infection for the past month. He is easily fatigued with insidious onset as well as easily bruising without bleeding, and denies blood in his stools. Vitals show no abnormalities, and examination shows diffuse lymphadenopathy. On the complete blood count, the white blood cell count is noted to be significantly elevated with a right shift. Peripheral smear demonstrates atypical lymphocytes, including flower cells. Which of the following is the most likely viral cause of the patient’s symptoms?