Studies: US gastroenteritis deaths, imported food outbreaks on rise

Mar 14, 2012 (CIDRAP News) – The number of US gastroenteritis deaths more than doubled in 8 years, with Clostridium difficile and norovirus as the two most common culprits, researchers reported today at an infectious disease conference.

The study of gastroenteritis deaths is the first analysis of its kind in the last 20 years. Investigators from the US Centers for Disease Control and Prevention (CDC) presented the findings at the International Conference on Emerging Infectious Diseases (ICEID) in Atlanta.

Among other foodborne illness topics presented at ICEID today, another group of CDC researchers reported on the growing role of imported foods in illness outbreaks.

Gastroenteritis death patterns
Gastroenteritis—inflammation of the stomach and intestines that produces vomiting and diarrhea—occurs with several foodborne illnesses as well as other infections such as C diff, a nosocomial illness that has been increasingly linked to settings outside of the hospital.

Aron Hall, DVM, MSPH, who led the study and is with the CDC's Division of Viral Diseases, said in a CDC press release that gastroenteritis is common but can be very serious. "By knowing the causes of gastroenteritis-associated deaths and who's at risk, we can develop better treatments and help health care providers prevent people from getting sick," he said.

For the gastroenteritis study, researchers analyzed data from the National Center for Health Statistics on gastroenteritis-related deaths that occurred from 1999 to 2007.

Over the study period, gastroenteritis deaths from all causes increased from nearly 7,000 to more than 17,000 per year. Adults older than 65 made up 83% of the deaths, and C diff and norovirus were the most common infectious causes of death, according to the study.

Investigators found a fivefold increase in deaths from C diff, and overall the disease was linked to two thirds of gastroenteritis deaths.

On average, norovirus was linked to 800 deaths each year, but deaths from the virus doubled in years when outbreaks were caused by new strains. The CDC said norovirus is responsible for more than 20 million infections each year and is the country's top cause of gastroenteritis outbreaks.

Hall said the study shows for the first time that norovirus is the second leading cause of gastroenteritis deaths. "Our findings highlight the need for effective measures to prevent, diagnose, and manage gastroenteritis, especially for C difficile and norovirus among the elderly."

Rising illnesses from imported food?
In the imported food study, other CDC researchers found that foodborne illness outbreaks linked to the products appeared to rise in 2009 and 2010.

Hannah Gould, PhD, lead author of the study and an epidemiologist with the CDC's Division of Foodborne, Waterborne, and Environmental Diseases, said in a CDC press release, "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."

The research team based its findings on an analysis of outbreaks reported to the CDC from 2005 to 2010. During that period, 39 outbreaks and 2,348 infections were traced to imported food from 15 countries. Almost half (17) of the outbreaks occurred in 2009 and 2010. Fish was the most commonly implicated food, followed by spices, which included fresh and dried peppers.

Gould said as the US food supply becomes more global, people are potentially exposed to pathogens from a wider array of sources. Besides just a rise in imported food outbreaks, the group also found that nearly half involved foods from countries that hadn't been linked to outbreaks before.

The CDC said US Department of Agriculture (USDA) figures show that US food imports grew from $41 billion in 1998 to $78 billion in 2007, with much of the growth from fruit and vegetables, seafood, and processed food. According to USDA estimates, as much as 85% of seafood in the United States is imported.

The types of food responsible for outbreaks in the CDC analysis seemed to mirror the most commonly imported foods.

She said the group's findings probably underestimate the true number of imported food outbreaks, because the origin is sometimes not known or not reported. "We need better and more information about what foods are causing outbreaks and where these foods are coming from," Gould said. "Knowing more about what is making people sick will help focus prevention efforts on those foods that pose a higher risk of causing illness."

Over the past few years, the US Food and Drug Administration (FDA) has launched several efforts to improve the safety of imported food. For example, it has launched a Web-based screening system for imported food and drugs and unveiled a new strategy. The 2011 FDA Food Safety Modernization Act mandates that the agency inspect at least 600 foreign food facilities by the end of the year, with plans to scale up the inspections over the next 6 years.

More studies: Campylobacter GBS connection, Salmonella subtype patterns
Among several other foodborne illness presentations at ICEID today, other research groups unveiled more evidence that foodborne illness is an important cause of Guillain-Barre syndrome (GBS) and that outbreaks from different Salmonella serotypes are linked to exposure to different foods.

In the GBS study, researchers from New Zealand explored the relationship between hospitalization from Campylobacter infection and GBS and whether GBS incidence followed the decline in the country's campylobacteriosis rates, according to the study abstract. The group explored hospital data for GBS, Campylobacter infections, and other conditions for 1988 through 2010.

They found that, for the period from 1989 through 2008, GBS hospitalizations were closely linked to Campylobacter illness reports. Patients hospitalized with campylobacteriosis had an increased risk of GBS hospitalization in the following month.

Interventions to curb Campylobacter in fresh poultry led to a 52% decline in Campylobacter infections and a 13% drop in GBS hospitalizations in the 3 years after the measures were introduced.

The researchers concluded that their findings provide more evidence that Campylobacter infection is an important cause of GBS and that regulatory measures can yield important health and cost-saving benefits when infections and GBS are prevented.

In the Salmonella study, CDC researchers examined patterns in food vehicles in outbreaks caused by different serotypes. They reviewed Salmonella outbreaks with a single known serotype reported to the Foodborne Disease Outbreak Surveillance System from 1998 to 2008. They limited their analysis to outbreaks that involved only a single food commodity.

Of 1,193 outbreaks with a single Salmonella serotype, 34% (403) were linked to a single commodity. The researchers found that eggs accounted for 65% of Enteritidis outbreaks and that poultry was most commonly implicated in events involving Typhimurium, Newport, Heidelberg, Saintpaul, and Hadar serotypes. All outbreaks cause by Litchfield and Poona subtypes were linked to fruits and nuts.

Of serotypes that caused more than five outbreaks, Typhimurium, Newport, and Javiana had the widest range of commodity groups, and the lowest were Enteritidis, Heidelberg, and Hadar.

The group concluded that there are differences in food commodities and their links to different Salmonella strains, which suggest that the serotypes have different reservoirs. Keeping the differences in mind could help guide outbreak investigations and control measures, they added.

See also:

Mar 14 CDC press release on gastroenteritis deaths

Mar 14 CDC press release on imported foodborne illnesses

Baker MG, Kvalsvig A, Zhang J, et al. Guillain-Barre syndrome incidence declines following successful countrywide control of campylobacteriosis. 2012 ICEID online abstracts, page 193

Jackson BR, Griffin PM, Cole D, et al. Different Salmonella serotypes vary widely in predominant food source and in range if implicated food commodities: data from outbreaks, United States, 1998-2008. 2012 ICEID online abstracts, page 185

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