Hundreds of children became infected with HIV due to poor healthcare practices such as using dirty needles and contaminated blood in southern Pakistan, according to a study.
Doctors looked at the medical data of 31,239 people in the city of Ratodero in Sindh province, who agreed to take part in the research.
Out of that group 930 were positive for HIV, with 763 of them younger than 16 and 604 of those under five.
The doctors are urging Pakistan's government to do more to understand how the virus went from high-risk groups – such as drug users and sex workers – to the general population.
They warned there is not enough medication in Ratodero, where 591 children are registered for HIV care.
Doctors have also said the HIV outbreak in the city is extremely worrying and called it "one of the worst" in Pakistan.
The study was published in the international Lancet Infectious Diseases journal.
By the end of July, when the study was completed, only one in three children had started antiretroviral treatment "due to an inadequate supply of drugs and a lack of trained staff".
The study said 50 of the children examined were showing signs of "severe immunodeficiency" but did not specify if they have full-blown AIDS.
The doctors said in a statement: "The results, which are the first scientific report on the outbreak, appear to confirm observations … that HIV was mostly transmitted to children as a result of healthcare providers using contaminated needles and blood products."
Doctor in Pakistan suspected of malpractice after HIV outbreak in hundreds of children
Around 500 people have been affected in the outbreak, with the majority of cases being found in children.
Dr Fatima Mir from Aga Khan University in Karachi, the provincial capital, is one of the authors of the study quoted in the statement.
She said: "Pakistan has experienced a series of HIV outbreaks over the past two decades, but we've never before seen this many young children infected or so many health facilities involved."
The study was completed after Dr Muzaffar Ghangro, a paediatrician, was arrested during an investigation into the outbreak of HIV in hundreds of children in Sindh.
About 70% of Pakistan's 220 million people use the private healthcare sector, which is mostly unregulated and rarely monitored for cleanliness and safety.
Popular belief among Pakistanis is that intravenous or intramuscular injections are more effective that medicine taken by mouth, which has increased the use of syringes across the country – and the likelihood of dirty needles being used.
The doctors' statement said the government did act quickly in the immediate aftermath of the HIV outbreak in Ratodero, closing three blood banks as well as 300 clinics run by untrained medical staff.