Dozens of blood banks in Peru have been closed after at least four people were infected with the HIV virus through contaminated transfusions.
Judith Rivera's public plea alerted officials to the crisis
The government said all 240 of the country's facilities would be thoroughly screened, amid what is being described as a national emergency.
The patients were all infected at a hospital in the port city of Callao.
Officials insisted Peru's blood banks met international standards and urged people to continue giving blood.
"We do not want people to panic, what we have to do is be more careful, strengthen our care [of patients]," said Health Minister Carlos Vallejos.
The crisis was prompted after 44-year-old Judith Rivera contacted the media earlier this week to say she had been infected with HIV during a routine operation.
Mrs Rivera, a mother of four, said she was taking legal action to claim compensation.
"What is done is done, as they say, and a life has no price tag," she said during a news conference.
Health officials later revealed that three other patients had been infected with the virus after having blood transfusions at the same hospital - one of them a child aged 11 months.
The Washington-based Pan American Health Organization says its latest figures show that up to a quarter of the blood in Peru's banks is not properly screened.
In a further blow to the health system, officials also confirmed that 30 patients who attended a dialysis treatment centre had been infected with Hepatitis C.
The BBC's Dan Collyns, in Lima, says Peruvians are alarmed and are avoiding public hospitals.
He says the government's response to the crisis is unlikely to restore public confidence in the country's flagging health service.