AKIPRESS.COM - Spain has issued an international alert after the number affected by the country's biggest ever listeria outbreak rose to 150, Sky News reports.

A 90-year-old woman has been killed by the infection as the health ministry said it was checking another 523 suspected cases of listeriosis.

The spread has sparked fears in Spain, which is visited by around 80 million tourists a year.

Listeriosis is usually caught from eating food containing listeria bacteria.

It can be found in many types of food but is mainly a problem with unpasteurised milk, soft cheeses and chilled ready-to-eat snacks like pre-packed sandwiches.

Most confirmed cases in Spain have been recorded in the southern region of Andalusia, where a packaged pork plant linked to the outbreak is situated.

But there have been other cases as far away as Catalonia in the northeast, where around 50 people remain in hospital.