Australia's top-rating radio host, Alan Jones, is back in hospital just a few months after he returned to the airwaves.

The veteran broadcaster went off the air last Friday and was taken to hospital with an infection this week.

"Good morning, back in hospital with a nasty bug," Jones posted on his Facebook page on Friday.

Jones said he was recovering slowly and would not be back for at least another week.

"I wound up in intensive care but now recovering well," he said.

"Feel like I've gone 15 rounds with [boxer Muhammad] Ali."

Jones, 75, was forced to take a four-month break from his show on Sydney's 2GB radio in November last year for operations on his neck and back.

He returned to work on March 27.

The high-rating host's lengthy absence hurt ratings for the station.

Macquarie Media suffered a 1.6 per cent drop in the Sydney breakfast slot in the first radio ratings survey of the year, across the January 22 to March 4 period, market research company GfK reported.

AAP