The number of people in Ilkley suffering from a gastro-intestinal illness caused by the giardia lamblia parasite has risen to 46.

Dr Martin Schweiger, consultant in communicable disease control at the West Yorkshire unit of the Health Protection Agency, said: "Cases are continuing to come to our attention - there are now 46 people who have tested positive for giardia.

"We are continuing to encourage people to contact their GP if they feel unwell. If someone has already tested negative for giardia but their symptoms persist, then they should go back to their GP to be tested again.

"We have alerted family doctors in the local area to look out for people showing signs of the illness - which are diarrhoea, gas or flatulence, indigestion, nausea and stomach cramps."

The Health Protection Agency and Bradford Council's environmental health department are continuing to investigate the cause and source of the outbreak.

The Saffron restaurant in Staion Plaza Ilkley, is the current focus for these investigations. The water supply to Ilkley and several other possible environmental sources of giardia lamblia have now been excluded as sources for this outbreak.

Dr Schweiger added: "The spread of gastro-intestinal infections can be limited by ensuring thorough handwashing, especially when preparing food, after using the toilet (including nappy changing) and during and after contact with animals."

Giardia lamblia is quite rare in the UK and can be spread by direct contact with infected animals or humans, particularly where good hand washing procedures are not followed, or by consumption of infected water, food or beverages. People may also be infected by swimming in contaminated water.

Once diagnosed, it can be treated by GPs but there is an incubation period of up to 25 days between people contracting the infection and symptoms showing.

Anyone with diarrhoea needs to be particularly careful with their personal hygiene so they do not infect others and if they are food handlers or health care workers they should seek advice about continuing to work while they are ill.