Pope Benedict XVI left his seat as the head of Roman Catholic church. He cited health reasons, noting that he was no longer strong to continue.

A secret meeting, and echoes of Benedict’s exit, have heightened talk that Francis could resign, too. But the possibility is anyone’s guess.

(AP Photo/Gregorio Borgia) FILE-- A mosaic icon of Pope Francis is lifted to be placed next to the icon of Benedict XVI inside St. Peter and Paul’s Basilica in Rome, Monday, Dec. 9, 2013. (AP Photo/Alessandra Tarantino) FILE-- The tapestries showing late ...

The resignation of Pope Benedict XVI has demonstrated the process by which a pope might step down and be replaced.

Concerns over Pope Francis' health have mounted in recent years as have questions about his succession. Here's what we know.

The pope was admitted to hospital on February 14 where he is fighting a complex respiratory infection and pneumonia in both lungs.

The Vatican also released Francis' message for Lent, which runs from March 5 to April 17. The message, dated Feb. 6, encouraged Catholics to put themselves in the shoes of a migrant as an “examination of conscience.”

The Vatican says Pope Francis, who is hospitalized in critical condition with double pneumonia, was well enough to meet with Cardinal Pietro Parolin.

Despite his hospital stay, Pope Francis remains in charge of the Catholic Church. But what if his health continues to decline?

Francis was admitted to Rome's Gemelli hospital on Feb. 14 after a case of bronchitis worsened; doctors later diagnosed a complex respiratory infection, involving bacteria, virus and other organisms and the onset of pneumonia in both lungs on top of asthmatic bronchitis. They prescribed “absolute rest.”

Pope Francis marked the one-week point Friday in his hospital stay, getting up to eat breakfast as the 88-year-old pontiff continued fighting pneumonia and a complex respiratory infection, the Vatican said.