Dr Mathilde Jachym is pushing a trolley down a corridor at the sanatorium. Here over 60 patients are being treated for TB at any one time.
Jachym is worried about one of her patients who has not been eating enough. Some of them have developed drug-resistant TB, which is difficult to cure.
"This type of TB is difficult to treat because it need other drugs which are less tolerated," says Dr. Jachym, "we have to give patients this drug for a long time."
In the 1980s many thought TB would disappear in France thanks to better living conditions and medicine. But doctors have observed a slight increase in the number of cases in the 21st century. Today cases of tuberculosis are still very rare in France. There are eight cases for every 100,000 inhabitants.
The illness kills two million a year worldwide.
Jachym says tuberculosis is linked to poor living conditions.
"People who have social problems tend to postpone going to the doctor," she says. "So tuberculosis can grow and grow. And when they come to the doctor, they often have developed very severe case of tuberclosis."
Patients with social problems also struggle to keep to the treatments given to them.
In the Petit Fontainebleau's garden, patients sit on benches soaking in the sun.
A French pensioner chats with Maka Traoré, a patient from Mali. Life at the sanatorium is pleasant, but many patients know that once they recover and leave, life gets more complicated.
Traoré is an undocumented worker and is not looking forward to leaving the sanatorium.
" I don't have a home and I don't have any work," he says. "I wanted to work here to send money to my family back home. It's very difficult to find work."
Traoré admits it will be difficult to follow his TB treatment when he leaves the sanatorium. For the sanatorium’s French teacher Régine Lavaux, it is frustrating to let patients leave and return to their problem. Many struggle to take care of themselves.
Some patients get over problems such as alcohol abuse while they are at the sanatorium. However, they often relapse outside.
"They leave hospital, and sometimes a few weeks, a few days afterwards, we get a call and they are completely drunk," says Lavaux. "And all that we have done is destroyed."
Staff at the sanatorium know much of the fight against TB takes place outside their walls. France's last remaining sanatorium still has a lot of work ahead.