A UN report says Pakistan now has the second-fastest growing rate of HIV in Asia. (Representational)

The Pakistan government has sought the help of the World Health organisation (WHO) to probe the recent outbreak of HIV in the country's Sindh province, that has till now affected over 600 people, mostly children, according to a media report.

Till now, 681 HIV positive cases have been identified among the 21,375 tested in Ratodero town of Larkana district in the north-west part of the province. Out of the affected, 537 are between the ages of 2 to 15.

Health officials have attributed the cause to the use of unsanitary equipment, unsafe blood transfusion and rampant malpractice often at the hands of quacks.

"We are expecting a 10-member rapid response team from the WHO and Centres for Disease Control and Prevention (CDC) to arrive in a few days and we will be able to know the exact reason for the outbreak of the disease in Ratodero," Zafar Mirza, Special Assistant to the Prime Minister on National Health Services, was quoted as saying by the Dawn newspaper.

The CDC is a leading public health institute in the US and works with several public health institutions in Pakistan.

"We have a hypothesis that they became infected with HIV either through unscreened blood transfusions or usage of infected syringes as they are usually re-packed and re-used in unhygienic conditions. Third reason could be the lack of infection prevention and control and unprotected sex," he said.

Police last month arrested a doctor for allegedly transferring the virus to his patients. Seventeen quacks in the district were also arrested and their clinics sealed earlier this month.

Mr Mirza said they have ordered 50,000 more HIV test kits to screen all possible patients and three more HIV treatment centres being planned in Mirpurkhas, Nawabshah and Hyderabad in the province.

He said that the number of reported HIV cases in Pakistan was much lower than the actual number of cases.

According to estimates, 163,000 people were infected with HIV in the country but only 25,000 were registered with state-run HIV programmes and out of that, only about 16,000 came regularly for treatment and medicines.

He recalled that there had been HIV outbreaks in the country in the past, including in Sindh in 2016 and in Punjab in 2008.

"Our problem here is that HIV is seen as a big stigma. We need to deal with it with frankness," Mr Mirza said.

According to a UN report, Pakistan now has the second-fastest growing rate of HIV in Asia, with about 20,000 new infections in 2017 alone.