Severe stomach pains the earliest sign of trouble

Hundreds of types of E-coli bacteria exist, mostly in animal intestines. One is a killer.

The strain, known as O-157, and first discovered in humans only in the past decade, is responsible for Japan's mass food poisoning epidemic.

The bacteria causes severe symptoms when it finds its way into humans.

The first sign that anything is wrong is usually wrenching stomach pain followed by severe diarrhoea.

As the illness takes hold blood appears in the stools.

If the cause of the symptoms is recognised at this stage, antibiotics are often effective in bringing about a cure.

What are more dangerous are the secondary symptoms, which can be fatal.