Pope John Paul has spent a second night in the hospital after being taken ill with an acute respiratory infection. He is not said to have had any problems during the night.

The Vatican's chief spokesman, Joaquin Navarro-Valls, said Thursday morning the pope has been responding well to treatment and medical tests have given satisfactory results.

The pope was rushed to Rome's Gemilli hospital Tuesday night with breathing problems linked to the flu. Hospital sources said his second night at the hospital was a quiet one without any problems.

The Vatican insists there is no cause for alarm over the pope's health but doctors remain on guard for any complications. A top Vatican official said he expected the pope to stay in hospital for a full week.

Well-wishers went to mass at a chapel inside Gemelli hospital this morning while Catholics around the world have been saying special prayers for the pope's recovery.

"His health is important. We prayed for the pope," said one well-wisher. "We want him alive, said these pilgrims."

There has been much concern over the pope's health in recent years. His frailty and suffering has been visible to all.

The 84-year-old Pope, once known as God's athlete, suffers from arthritis and Parkinson's disease, which have steadily reduced his mobility and ability to speak clearly.