Hospitals have made good progress in fighting infections on wards and the number of cases has fallen in recent years as awareness has increased, an expert has said.

While the outbreak caused by the bacteria pseudomonas at Belfast's Royal Maternity Hospital was "tragic" for the babies involved, it did not necessarily signify that such cases were on the rise, said Dr Martin Wiselka, a consultant in infectious diseases.

"There's always more that can be done but actually we've made really good progress in the last few years," he said.

"We've reduced the rates of MRSA nationally over the last few years and rates of Clostridium difficile have come down a great deal."

Norovirus - known as the winter vomiting bug - remains "quite a big problem" in hospitals but is difficult to prevent from spreading in any confined space, and overall there has been a decrease in hospital infections, he said.

This was attributed partly to government targets imposed on hospitals, a greater focus on infections and many more patients being screened for infections than previously.

There has also been more emphasis placed on cleanliness, with more alcohol gel present in hospitals than there was a few years ago.

And surveillance of infections means that if more than one or two cases are recorded in a particular area, "alarm bells start ringing and we start looking into it", the University Hospitals of Leicester NHS Trust consultant said.

"Doctors don't really like targets but I think they've probably helped here," he added. "There are always new challenges and ones like pseudomonas do appear from time to time. But this is a localised outbreak at one hospital and hopefully they'll be able to eradicate it."

But figures from the NHS Information Centre released last month reportedly showed that more people than ever picked up life-threatening infections while spending time in hospitals in 2010.

The number was said to have doubled from 22,488 to 42,712 in just two years.

And the Health Protection Agency said there were often outbreaks of a wide variety of bacteria and viruses on neonatal units due to the vulnerable and high-risk nature of the patients.

"Due to the complex nature of these sorts of units and long lengths of stay, it can take a relatively long time to get the outbreak under control, even when best practice is applied," a spokesman said.

Dr Wiselka added: "It just shows how we have to be on our guard and that hospitals are dangerous places because you've that combination of sick patients and nasty bacteria."