The blood recipient contracted the mosquito-borne illness during treatment for a gunshot wound in April 2015, according to the Campinas health department. Brazilian health authorities said Thursday that one of his blood donors had the Zika infection, Reuters reports.
Doctors originally believed the patient had dengue fever, and did not complete a blood test for Zika until Jan. 28.
The possibility of transmitting the virus through blood transfusions adds another method of Zika transmission, boosting the infection’s ability to spread. The World Health Organization declared the cluster of birth defects linked to Zika an International Public Health Emergency on Feb. 1, and estimates the total number of cases could reach 4 million by the end of the year.
Zika in pregnant women has been linked to cases of microcephaly in their babies, a birth defect in which the baby’s head is unusually small.