Will he survive the serious respiratory infection?
And if so, how able will he be to speak and act afterwards?
In addition to these anxious worries, many people are currently concerned about another question: What will happen in the Vatican?
As the oldest elective monarchy in the world, the Vatican has experience with such delicate phases: The head of Catholic Christianity is only able to act to a limited extent.
Death or resignation are conceivable at any time - but so too is a long period in a state of serious ill health.
What is possible now and what can follow next is relatively clear, but not completely regulated.
This includes the principle that there is no substitution for the core of the papal office.
This is why recent appointments of bishops or the confirmation of the first female head of government in the Vatican state have been publicised as current decisions despite the Pope's medical rest order.
A simple paraphe - currently an "F" - is enough to bring such acts into force.
Relief at the Synod on Synodality
Participants in the Synod on Synodality, who decided on reform ideas for the Catholic Church at the end of October, are now relieved that the Pope immediately approved their votes.
If he had announced a "post-synodal letter" first, as is usually the case, this might have been lost during the current illness phase of the pontificate - because no one other than the Pope would be allowed to write it.
The situation is different with the Holy Year: the machinery has been running ever since the opening bull was published.
Pilgrimages, the jubilee indulgence, the church services - all of this is also possible without Francis.
But something essential is missing: the personal encounter with the successor of the Apostle Peter, the Bishop of Rome.
Here, even a Pope who is only present in silence or via livestream would be a reason for the participants to celebrate.
The Vatican's attempts to disseminate the Pope's most recent speeches as texts have recently seemed ghostly. After all, it is precisely for Francis that the man with his personal charisma is the "message".
The charismatic man on the papal throne has attracted all eyes and ears from the very beginning. And there are hardly any other popular cardinals besides him who are capable of being a crowd-puller.
The latter also applies to the number two in the Vatican, Cardinal Secretary of State Pietro Parolin (70). In terms of foreign policy, the shrewd chief diplomat can represent the Pope, write greetings and give political speeches, as he did recently in Burkina Faso.
During the first four days of the papal hospitalisation, Parolin was in North West Africa and met secular and religious leaders there. And the "Substitute of the Secretariat of State", currently Archbishop Edgar Pena Parra (64) - also an inconspicuous deputy - is authorised to sign on current legal and property transactions.
A case that has never happened before
Cardinal Parolin would be a key figure in the event of the Pope's permanent incapacity. As Cardinal Secretary of State, he is the guardian of the "conditional declaration of resignation" that Francis signed in 2013.
If the Pope were permanently unable to act due to illness, Parolin could pull out this card and declare the Chair of Peter vacant. It is rumoured in the Vatican that the Pope recently had a flat for the sick built next to the Basilica of Santa Maria Maggiore for this eventuality.
There has never been such a declaration of impediment. It is therefore disputed among canon lawyers who would have to agree to it.
The consensus is that at least the dean of the College of Cardinals, currently Cardinal Giovanni Battista Re (91), would have to agree.
The highest-ranking member of the College of Cardinals would have the task of calling the cardinals from all over the world to Rome to elect a new pope in any case - even in the event of the pope's death or active resignation.
Unlike in the recent cinema film"Conclave", however, the cardinal dean would not then preside over the election in the Sistine Chapel.
This is because Re has long since passed the prescribed age limit of 80.
This task would currently fall to the "most senior" cardinal bishop - because the current vice-dean Leonardo Sandri is also over 80 years old.
And that in turn would be Cardinal Parolin.