The World Health Organization issued a call to action to China Monday over HIV/AIDS as government figures said nearly half a million people are living with the disease or its precursor, with hundreds of thousands more thought to be undiagnosed.

Bernhard Schwartlaender, the World Health Organization’s representative in China, wrote in an op-ed in the state-run China Daily newspaper that “there is much more China needs to do” to prevent infection and better help those living with HIV.

“Perhaps most importantly, we must eliminate stigma and discrimination towards people living with HIV, and at-risk populations such as men who have sex with men, sex workers, and injecting drug users,” Schwartlaender wrote.

“I’ve seen some of my own colleagues in the medical profession turn patients away because they disapproved of the person’s sexual orientation. That is simply unacceptable, and it has to stop,” he added.

The op-ed was published on World AIDS Day, a day after the National Health and Family Planning Commission said that by the end of October, a total of 497,000 people in China had been diagnosed with HIV/AIDS since the country’s first case in 1985.

The figure represents an increase from September 2013, when 434,000 people in China were known to be living with HIV/AIDS. But it was not clear whether the rise was due to an increase in infection, or more cases being diagnosed.

Another 154,000 have died from AIDS over the past three decades, the commission said.

China’s National Center for AIDS/STD Control and Prevention last year estimated that as many as 810,000 people are living with HIV/AIDS in the country, including those who have not yet been diagnosed, out of a total population of 1.36 billion.

That is a far lower proportion than India, where UNAIDS says there are more two million people living with HIV, in a slighter smaller total population — although UNAIDS does not give figures for China.

More than a quarter of a million HIV-positive people are currently on antiretroviral treatment in China, UNAIDS China director Catherine Sozi wrote in a China Daily op-ed on Saturday.

China “needs to increasingly go beyond its initial success in the roll-out of large-scale HIV programmes and focus on how to reach people who are currently falling through the cracks,” she wrote.