Two intensive-care patients at public hospitals in the Argentine province of Cordoba contracted HIV through blood transfusion, The Associated Press (AP) reports. The story was originally reported by local newspaper La Voz del Interior.

According to the AP, an unidentified donor gave blood at a Cordoba hospital in December, initially testing negative for HIV. When the donor returned in May to donate once again, his test came back positive. However, the blood had already been distributed, and two patients were infected through blood transfusions from the donor.

The AP reports that the initial test may have been taken during the 16- to 22-day window period between HIV exposure and the time antibodies can be detected in a standard blood test. During that time, the virus can still be transmitted.

The newspaper did not identify the donor, the hospitals or the infected patients in accordance with a national law forbidding disclosure of such information.