Extreme age and a past joust with tuberculosis place former South African president Nelson Mandela among the highest categories of risk when it comes to respiratory illness, experts said.
Mandela was released after two days of hospital care in Johannesburg for what was described as an acute respiratory infection.
He will now be treated at home, South Africa's surgeon general, Vejaynand Ramlakan, said.
Mandela's condition was stable and "he surprises us on a daily basis with his powers of recovery," he added.
Details about the illness were sketchy, and French lung specialists wondered whether part of the picture was being obscured for political reasons.
Patient of prime concern
But, they said, a man of Mandela's age and with his medical history would clearly be a patient of prime concern.
Mandela is 92 and, while imprisoned on Robben Island during the anti-apartheid struggle, had TB, which weakens the lungs and boosts the risk of respiratory disease.
"Anyone can catch a respiratory virus, but the impact is greater for elderly people compared with young people, and their condition can swiftly deteriorate," said Yves Martinet, a professor at the Brabois University Centre Hospital in Nancy, eastern France.
"However, if the patient responds well to treatment and the vital signs are good, it's preferable to continue treatment at home, with medical surveillance, a nurse, a kinesitherapist, rather than keep him in hospital, where there's the risk of catching germ strains" which are aggressive or antibiotic-resistant.
If, for instance, Mandela had had a viral infection and bronchitis, "the fact that he's been discharged after two days is rather positive," said Bernard Maitre, a professor of pulmonology at the Henri Mondor Hospital in the Paris region.
But Jean-Pierre Grignet, a department head at a hospital in the northern town of Denain, cautioned that a bout of illness at such an advanced age left its mark, even when successfully treated.
"Even if the infection is cured, the problem is a reduction in respiratory capacity," he said. "There is always a risk of a decline in general health."
(Reuters Health, January 2011)