Q&A: Cryptosporidium outbreak

Welsh Water customers in the Bangor area have been told to boil their drinking water after raised levels of the Cryptosporidium parasite were found in it. BBC News takes a closer look at the bug.

Why are customers told to boil drinking water?

'Elevated' levels of Cryptosporidium have been found in the water from Mynydd Llandegai water treatment works.

What does the bug do?

It causes gastro-intestinal illness with diarrhoea or sickness.

How long should the water be boiled for?

It is sufficient to bring the water to the boil and then allowing it to cool. Using an electric kettle is fine.

Use of drinks dispensers is not recommended unless the water is heated to at least 70C. Ideally, they should be turned off and disconnected from the water supply. When the water supplies are back to normal, the machine should be cleaned out before re-use, and any filters replaced and disposed of carefully.

When will the boil water notice be lifted?

When the water quality is back to an 'expected' standard for 10 days in a row.

Why are some areas being told to boil water for the second time in three years?

The problem this time was found in the Mynydd Llandegai reservoir. In 2005 it was in the Cwellyn reservoir. There are some households which receive water blended from the two.

So, although the source of the problem is different, households which receive water blended from both have been affected by both incidents. Households which receive water from Cwellyn only are unaffected this time.

Will Dwr Cymru be paying compensation?

Yes. As the boiling notices is expected to last over a week all customers affected will be given £25 to cover the 'cost and inconvenience'.

What is cryptosporidiosis?

It is a diarrhoeal disease of humans and animals caused by a microscopic parasite called Cryptosporidium. It takes up to a week for the illness to incubate, and no cases have emerged yet.

How is it spread?

It is spread by a variety of routes. Person-to-person spread is an important source of infection if care is not taken with personal hygiene. It is also spread through contact with farm animals (or sick pets) or through contaminated drinking water.

Hand washing is important after using the toilet, or as soon as possible after handing farmyard animals or sick pets, manure on the ground, or having contact with people with diarrhoea. Good hygiene is particularly important before handling food.

What about brushing teeth, bathing and washing up?

Brushing teeth - used cooled boiled water. Washing and bathing - it is safe to wash and take a bath - the route to infection is through swallowing the water.

Washing up - dishes should be washed using boiled water if possible, but it is probably sufficient to rinse washed dished with cooled water before they are dried. Dishwashers are unaffected if used on hot wash cycle.

What should I do if I become ill?

The infection usually clears up by itself in a healthy person, although this may take several days. Consult your GP if diarrhoea is unduly prolonged or if you are at all concerned. A GP should also be consulted if the person affected is very young, elderly or frail.