LUCKNOW, India -- A fake doctor treating poor villagers in northern India for colds, coughs and diarrhea has infected at least 21 of them with HIV by using contaminated syringes and needles, a health official said Tuesday. Sushil Choudhury, the official, said police were looking for Rajendra Yadav, who fled Bangarmau, a small town in Uttar Pradesh state, after the HIV infections were detected in December last year.

The villagers said they rarely saw Yadav changing the needles. Choudhury said that probably led to the spread of HIV.

With India's health care system facing a massive shortage of doctors and hospitals, millions of poor people seek fake doctors for cheap treatment.

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India had 2.1 million people living with HIV at the end of 2016, according to a UNAIDS report. Of those, 9,100 were children under age 15. India has registered a 20 percent annual decline in new infections over the past few years, according to the report.

Yadav would visit villages on his bicycle and treat patients outdoors. Villagers complained that he would give injections for almost all ailments for meager payments, Choudhury said.

A sudden spurt in HIV cases in and around Bangarmau detected in December last year alerted state authorities. "An investigation showed that almost all of them had taken injections from one person," Choudhury said. "This was an important lead. We set up special medical camps in villages in the area and checked 566 people, and 21 were found to be HIV positive."

Mehtab Alam, a project manager for Raza Hussain Memorial Charitable Trust, said that fake doctors do not use disposable syringes, instead using glass syringes and one needle to inject hundreds of patients. The group works with HIV and AIDS patients in the region.

"Villagers are ignorant about hygiene," he said.

HIV -- or the human immunodeficiency virus -- is transmitted through blood transfusion, use of infected needles and syringes, unprotected sex, or from mother to child. It weakens the body's immune system, making it susceptible to various infections. Over time, an HIV infection can develop into AIDS, a progressive failure of the immune system that leaves the body open to life-threatening infections and cancers.