When TB drugs first became available, the traditional method was oral delivery. But the clinical outcome was limited because the drugs were absorbed via the digestive tract, and so only a limited amount managed to reach the lungs and help close up the cavities.

In the 1950s, doctors attempted to use a nasal catheter to inject drugs into lungs directly.

The method was promising but proved unable to target the holes precisely.

At a time when modern equipment was a scarcity in most Chinese medical institutions, in order to develop a gadget that could shift valves in a desired direction, Ma enlisted the help of a surgeon and two other patients.

One of them, an aircraft maintenance technician, provided Ma with high-quality steel wire that could be used to make an adjustable spring.

The other, who repaired bikes for a living, gave her latex tubes to wrap around the steel as protection.

Ma said the invention of the directional catheters would not have been possible without the collaboration of her fellow doctors and the two patients, who pooled limited resources to work together toward conquering the disease.

Because of the insufficient daytime supply of electricity at the time, Ma sometimes had to begin treatment at four in the morning.

"I remember as it got closer to 4 am, patients waiting in the corridor would whisper to each other, 'let's quiet down so Doctor Ma can sleep a while longer'," she said.

One patient who benefited from the new technique kept in touch with Ma. In one letter to the patient, Ma wrote that "seeing patients receive the correct diagnosis and successful therapy is our greatest joy, and the spiritual anchor that motivates me to work harder".

Thanks to the firm conviction and dedication of healthcare workers like Ma, as well as improvements to the national TB prevention and control system, China's TB mortality rate has declined continuously, reaching 2.2 per 100,000 people in 2019. According to the WHO, the country has now dropped to 30th on the list of 30 high-burden countries for the first time.

With the development and rollout of more advanced tools, Ma said the age when doctors were constantly baffled and dismayed by poor diagnoses had passed, and Chinese TB patients have access to most drugs available globally.

Some things haven't changed though, such as Ma's heartfelt respect and genuine care for patients.

In the past, she had to trek to remote areas to visit rural patients, enduring rain and sunshine while grappling with outdated equipment and the shortage of medications.

Her team was used to putting spare change in their medication kits to help patients who could not cover the full cost of treatment.

Ma also developed the habit of warming up the stethoscope with her hands before placing it on a patient's chest or back, so that they wouldn't feel cold.

As she has said previously, "the doctor's greatest enemy is aloofness, and their best prescription is love".

On April 24, Peng Liyuan, wife of President Xi Jinping and the World Health Organization's Goodwill Ambassador for tuberculosis and HIV/AIDS, said in a reply to Ma Yu that she admired and was touched by her deeds.

"You have worked in the field of tuberculosis diagnosis and treatment, scientific research and education for 60 years and you have always been fighting on the frontline against the disease," the letter said.