Eating food contaminated with bugs leads to more than half a billion cases of illness a year, the World Health Organization warns.

It says this "global threat" contributed to 351,000 deaths in 2010. Unsafe foods, for example undercooked meat, can cause 200 problems - from diarrhoea to cancer.

But changes in food production mean there are more opportunities for meals to harbour harmful bugs or chemicals, experts say.

A local food problem can quickly turn into an international emergencyDr Margaret Chan, WHO.

Culinary caution

Unsafe foodstuffs can contain many types of harmful bacteria, viruses, parasites or chemicals.

Examples include undercooked meat, fruits and vegetables contaminated with faeces and shellfish containing marine toxins.

But the WHO says investigating these outbreaks has become increasingly challenging as single plates of food often have ingredients from many countries.

In its first WHO report on this issue, its director-general Dr Margaret Chan warns: "A local food problem can quickly turn into an international emergency.

"Food production has been industrialised, and its trade and distribution have been globalised.

"These changes introduce multiple opportunities for food to become contaminated with harmful bacteria, viruses, parasites or chemicals." The analysis, which pulls together scientific literature from across the globe, shows:

Most deaths are caused by pathogens such as salmonella, E. coli and norovirus

The majority of lives lost are in Africa and South East Asia 40% of the deaths are among the under-5s, the most vulnerable group

Raw hazards

Experts say illnesses caused by food also carry major economic risks. They estimate the E. coli outbreak in Germany in 2011 cost about US$1.3bn (£876m) in losses for farmers and industries.

WHO leaders are calling on governments to urgently strengthen food safety systems.

On April 7, the WHO launches its food safety campaign, From Farm to Plate. It aims to prompt the public and governments to consider where individual ingredients in meals come from and question whether these are properly and safely handled at every stage.

How to be food-safe:

Wash hands, surfaces and equipment before preparing food

Separate raw and cooked food - use separate utensils for handling raw foods

Safe temperatures - do not keep cooked food at room temperature for more than two hours. Keep food piping hot (above 60C) before serving Use safe water to wash raw fruit and vegetables