New research released by the US Centers for Disease Control and Prevention this week shows foodborne disease outbreaks in the US that were tied to imported foods appeared to rise in 2009 and 2010, with nearly half of them linked to imports from regions that had not been associated with outbreaks before.

The CDC researchers who presented their findings at the International Conference on Emerging Infectious Diseases in Atlanta on 14 March, said so far, the most common imported foods linked to disease outbreaks were fish and spices.

Research team member Dr Hannah Gould, an epidemiologist in the Division of Foodborne, Waterborne and Environmental Diseases at the CDC, told the press:

“It’s too early to say if the recent numbers represent a trend, but CDC officials are analyzing information from 2011 and will continue to monitor for these outbreaks in the future.”

For their research, Gould and colleagues reviewed outbreaks reported to the CDC’s Foodborne Disease Outbreak Surveillance System.

Through this system the CDC collects reports of foodborne disease outbreaks due to enteric bacterial, viral, parasitic, and chemical agents.

The reports are filed by state, local and territorial public health agencies through the National Outbreak Reporting System (NORS).

Gould and colleagues found 39 outbreaks and 2,348 illnesses reported to the Surveillance System during 2005 to 2010 were linked to imported food from 15 countries.

For that five-year period, nearly half of the outbreaks (17) happened in 2009 and 2010.

Over the five-year period, fish was the most common source (tied to 17 outbreaks), followed by spices (tied to 6 outbreaks, 5 of which were linked to fresh or dried peppers).

Nearly 45% of foods linked to the outbreaks were imported from Asia.

Gould said that as the food we eat increasingly comes from all over the world, there is a greater risk of people being exposed to germs from all over the world too.

“We saw an increased number of outbreaks due to imported foods during recent years, and more types of foods from more countries causing outbreaks,” she added.

The types of food causing the outbreaks align closely with the types of food that were most commonly imported.

Figures from the US Department of Agriculture’s (USDA’s) Economic Research Service (ERS) show that US food imports have nearly doubled from £41 billion in 1998 to $78 billion in 2007.

A lot of the growth has been in imported fruits and vegetables, plus seafoods and processed foods. The ERS figures also show that 85% of seafoods eaten by Americans comes from outside the country. Also, depending on the season, up to 60% of fresh food eaten in the US is imported.

Gould said their analysis probably does not show the true number of disease outbreaks caused by imported foods, due to under-reporting.

She said we need to collect more information on the types of food that are causing outbreaks and their origin.

“Knowing more about what is making people sick, will help focus prevention efforts on those foods that pose a higher risk of causing illness,” she urged.

The Food and Drug Administration (FDA) has recently increased environmental assessments to find out the root causes of foodborne disease outbreaks, with a view to using the information to help prevent outbreaks.

A new piece of FDA legislation, the Food Safety Modernization Act, should also lead to better ways of preventing foodborne diseases from both domestic and imported foods.

You can search the CDC’s Foodborne Disease Outbreak Surveillance System database with the web-based FOOD tool, which lets you see national information and limited descriptive summaries of outbreak data.

Written by Catharine Paddock PhD