A health trust in Sussex is at a loss to explain why rates of MRSA infection suddenly jumped up at the start of 2006 after nine months of steady decline.
The Princess Royal Hospital in Haywards Heath is run by the trust
Brighton and Sussex University Hospitals NHS Trust reported 42 cases from January to March this year, up 13 from the last three months of 2005.
It said there was no "obvious identifiable reason to explain this".
The trust's target set by the Department of Health is to have only 43 MRSA cases in total by 2008.
Before the recent sharp rise, the trust said it had been showing "a reduction towards the target trajectory".
There were 36 cases from April to June 2005, 33 from July to September and then 29 from October to December.
The first MRSA results for 2006 were discussed by the trust's board on Tuesday.
Its monthly meeting also heard the latest financial figures and forecasts.
The trust is reporting an £11.3m year-end deficit for 2005/06.
It is also projecting a continued deficit of £9.3m for the current financial year up to the end of March 2007.
However, the trust said this was consistent with its turnaround plan.
It also said its current monthly deficit was £1.4m, and that it would continue to need external support until late 2007 when it expects to be breaking even on a monthly basis.
The trust runs five hospitals and in March announced plans to cut 325 jobs.