Hospital scalpers are a disease China has been working to cure for years.

Commonly known as huangniu, or yellow bulls, these crooks book appointments at major public hospitals - preventing genuine patients from doing so - and then illegally sell them on at vastly inflated prices.

Those unwilling to pay up face a lengthy wait, potentially putting their lives at risk.

A registration ticket to see a specialist in Beijing, for example, costs roughly 100 yuan ($15). Yet in October, the city police found dozens of scalpers hawking such appointments for at least 2,000 yuan.

Victims are often those who have traveled far from their hometown to see an experienced doctor at a top facility, according to a vascular surgeon at a prestigious Beijing hospital who did not want to be identified.

"Those from outside Beijing will often pay the scalper's price rather than wait a few days, as that would cost them even more," he said.

In addition to snapping up appointments, some scalpers also try to persuade patients to seek treatment at a different hospital, which pays kickbacks to those who bring in "customers". They often pretend to be sick or familiar with a particular doctor to earn the patients' trust.

The problem of scalping has slowly grown into a black market industry, yet it has been dealt a heavy blow in recent years as legislators and political advisers - including those now attending the two sessions of the National People's Congress and the National Committee of the Chinese People's Political Consultative Conference - have tested out various solutions.

Some health institutions have extended the operating hours of their busiest departments, while many hospitals have also introduced a "real name" registration system that requires patients to provide an identity card when making an appointment. Doctors are instructed to recheck the information before a checkup and to raise the alarm if it doesn't match.

Mobile apps also now allow people to book appointments directly using an automated system, in an effort to remove middlemen from the equation.

In mid-2016, Beijing's public security authority urged public hospitals to upgrade their security camera systems and pledged to respond to any complaints about scalpers, according to Xinhua News Agency.

Since then, there have been several reported cases, including one in October in which police detained 54 scalpers accused of manipulating online booking systems after a two-month investigation at five hospitals, including Peking University Third Hospital.

Thirty-seven received administrative detentions, an extrajudicial punishment that can last up to 15 days, while the others were still awaiting criminal prosecution, the authorities said.

Yet outside the capital, problems persist.

In April, nurse Luo Fuyu at the Nanjing Maternity and Child Health Care Hospital became an online celebrity after a viral video showed her confronting a female scalper.

Zheng Mingfei, the hospital's security director, said afterward, however, that administrators have no effective way to penalize scalpers. All they can do is ask them to write a letter promising to stay away.

"There's no law to which we can refer to punish them," he said, adding that if the hospital calls the police, the scalper is usually simply told to repay the money to the scammed patients.

"Hospitals that collaborate with scalpers must be punished, and we need regulations and laws to severely punish them. That's the only way to rid hospitals of scalpers," he added.

His comments echoed a China Daily editorial a month earlier that complained few people had received severe penalties, and that it was an "open secret" that some hospital employees helped the scalpers.

"They are ... the root cause of the chronic disease," the editorial said, calling for "zero tolerance" toward such activities.

As with any tricky disease, the treatment will only be truly effective if it attacks the root cause, not just the symptoms.