About 200 patients a day are visiting the hospital's A&E section

Derriford Hospital in Plymouth says it is doing its best to cope with the increase, but hospital staff do not know what is behind the increase.

The numbers have risen from 170 patients a day to 200, while on some days there have been as many as 250 patients seeking attention.

The hospital says this is a rise of about 17% over the last year.

Derriford is not the only South West hospital noticing an increase.

Localised problems

The Royal Devon and Exeter Hospital at Wonford has seen a rise of about 6% over a similar period.

Meanwhile, the Royal Cornwall Hospital at Treliske says it has seen a 20% increase in admissions since 1998 from holidaymakers and other people from out of the area.

Very little statistical work has been done so far by the National Health Service to work out where the rises are coming from.

Localised problems like outbreaks of the Norwalk virus can have a major but short-term impact.

However, there is no obvious problem at Derriford Hospital at the moment to explain the recent increase.