Is migration considered desirable for the sick, and what is the ruling if his illness worsens due to migration, with no treatment available in the country of migration to which he intended to preserve his religion?

Migration from lands of disbelief to lands of Islam is obligatory if a Muslim is unable to openly practice his religion or fears fitna (temptation/tribulation), unless there is an impediment, such as an inability to migrate due to severe illness. People regarding migration are of three types: one upon whom migration is obligatory, who is capable and unable to openly practice his religion; one upon whom there is no migration, who is incapacitated by illness or weakness; and one for whom migration is desirable, who is capable and able to openly practice his religion, but migration is desirable for him to enable him to participate in jihad and increase the Muslim population. Illness is an excuse in obligatory migration if it incapacitates the person from undertaking it. However, if a person is capable of migrating but fears an increase in illness because of it, then his excuse is not valid. An illness that occurs after migration is subject to the same ruling as other illnesses, and this happened to some companions of the Prophet, peace and blessings be upon him, after the migration to Medina. A sick person may move to another country where he can find treatment, provided he is able to openly practice his religion.