Health Minister Carlos Vallejos said Thursday the blood banks will be inspected by a commission that will include officials from the World Health Organization (WHO).
"This situation cannot continue," Vallejos told a news conference. "All of Peru's blood banks are being reviewed."
A Health Ministry investigation found that Judith Rivera, a 44-year-old mother of four, was infected with the virus after receiving blood transfusions during an operation for a tumor in her uterus in April at a state hospital in Callao, Lima's port city.
Vallejos confirmed three other cases, including that of an 11-month-old infant, all at the same hospital.
On Thursday, a 17-year-old boy told local media that he was also infected with HIV after receiving a transfusion at the hospital, but the ministry had not yet confirmed the case.
Jose Cruz, an adviser on blood and laboratory safety for the Washington-based Panamerican Health Organization, called Peru's blood banks "worrying."
He said Peru is the organization's list, along with Bolivia, Colombia and Mexico, of countries that fail to perform preliminary disease screening all blood collected in blood banks.
The organization's most recent figures show almost a quarter of the blood Peru's banks receive is not properly screened, Cruz said.
Vallejos said Peru fulfills international standards for blood donation screening.
The United Nations estimates that some 93,000 of Peru's 27 million people are HIV positive.
Testing each unit of donated blood for HIV began in 1985, and tests for HIV are now used on all donated blood. With improved testing for HIV, the number of transfusion-related AIDS cases continues to drop. The risk of HIV transmission through transfusion is about now about one in 2,135,000.