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Norovirus, Salmonella Key Culprits in CDC Outbreak Report

Norovirus remained the most common foodborne disease in 2008, but more people were hospitalized for Salmonella poisoning than any other food-related illness, the Centers for Disease Control and Prevention (CDC) says in its annual report on foodborne illness.

Poultry, beef and fish were once again implicated most often as the source of outbreaks, according to the summary.

Those findings, published Thursday in the CDC’s Morbidity and Mortality Weekly Report, are from cases reported by states to the national Foodborne Disease Outbreak Surveillance system for 2008, the most recent year for which the information is complete. 

There were 1,034 foodborne disease outbreaks with 23,152 confirmed illnesses, 1,276 hospitalizations and 22 deaths reported in 2008, the CDC said.  Of course, the actual toll was much higher because only a fraction of foodborne illnesses are diagnosed and reported.

The CDC said the number of 2008 outbreaks was 10 percent lower than the annual average (1,151) reported for 2003–2007, and the number of related illnesses was 5 percent lower (down from 24,400). Salmonella, E. coli and Listeria infections were up in 2008 compared with the 2003-2007 average, while the number of most other bug-caused illnesses remained steady or decreased.

 

Norovirus was the most common confirmed cause, blamed for 49 percent of outbreaks and 46 percent of illnesses. Norovirus outbreaks often are the result of widespread exposure, the CDC said, because more than one food can become contaminated by food workers who may be shedding norovirus in their stools and haven’t properly washed their hands. Leafy greens used in salads are the most easily contaminated, the report noted.

Salmonella was responsible for 23 percent of outbreaks and 31 percent of confirmed illnesses. It was the most deadly pathogen, and also the cause of more than half the multistate outbreaks in 2008. Of the 17 outbreaks that crossed state lines, Salmonella caused nine of them. The source foods were identified in six of those outbreaks: cantaloupes, cereal, ground turkey, ground white pepper, jalapeno and serrano peppers, and peanut butter/peanut paste.

The CDC predicted new efforts may curb Salmonella, citing the new shell-egg regulations imposed last year and lower Salmonella-tolerance limits for young chicken and turkey carcasses, which took effect in July.

Shiga toxin–producing E. coli caused the second highest number of hospitalizations (17 percent), followed by norovirus (7 percent). Outbreaks caused by Clostridium botulinum resulted in the highest proportion of hospitalizations (90 percent), followed by Listeria outbreaks (76 percent).

E. coli O157 caused six multistate outbreaks in 2008; ground beef was the source in two of them. Two other multistate outbreaks, linked to sprouts and Mexican-style cheese made from pasteurized milk, were the result of Listeria contamination.

Among the 22 deaths confirmed to be linked to outbreaks of foodborne illness, 13 were attributed to Salmonella, three to Listeria monocytogenes, three to Shiga-toxin producing E. coli (two O157, one O111), and one each to Staphylococcus, norovirus and mycotoxin.

The number of E. coli O157 and Salmonella Enteritidis (SE) outbreaks in 2008 exceeded the government’s Healthy People 2010 food safety goal of reducing outbreaks caused by certain foodborne bacteria. The 35 outbreaks caused by E. coli O157 were more than triple the Healthy People 2010 target of 11, and the 29 outbreaks attributed to SE exceeded the target of 22 by nearly a third.

There were 218 outbreaks linked to single food commodities, led by poultry (15 percent of outbreaks), beef (14 percent), and finfish (14 percent), numbers the CDC said haven’t budged over the past decade.  But in terms of numbers of outbreak illnesses, fruits and nuts (24 percent), vine-stalk vegetables (23 percent ), and beef (13 percent) were the major suspects.

The bad bug-food combination linked to the most outbreaks was norovirus in leafy vegetables (18), while Salmonella-tainted vine-stalk vegetables were blamed for the most illnesses (1,604), followed by Salmonella in fruits or nuts (1,401).

Where did people get contaminated food? In 52 percent of the 868 outbreaks that could be linked to a single location, the source was a restaurant or deli and 15 percent were the result of home-cooked meals, according to the summary.

Information from the annual surveillance reports offers insight into what causes foodborne illness outbreaks so that prevention efforts can target the pathogens and susceptible foods, the CDC said.

The summary authors cautioned that the findings have several limitations, including that only a small proportion of foodborne illnesses reported each year are associated with outbreaks. And for every confirmed foodborne illness, many more go unreported. The CDC estimates that tainted foods cause 48 million illnesses, 125,000 hospitalizations and 3,000 deaths annually in the United States.

2008 Foodborne Outbreaks, Bacterial Illnesses:

 1. Salmonella – 117 outbreaks with 4,960 illnesses

 2. Clostridium perfringens – 40 outbreaks with 1,409 illnesses

 3. E. coli (both O157 and non) – 36 outbreaks with 920 illnesses

 4. Campylobacter – 25 outbreaks with 615 illnesses

 5. Bacillus cereus – 15 outbreaks with 122 illnesses

 6. Staphylococcus enterotoxin – 14 outbreaks with 311 illnesses

 7. Shigella – 6 outbreaks with 170 illnesses

 8. Clostridium botulinum – 4 outbreaks with 10 illnesses

 9. Listeria – 3 outbreaks with 33 illnesses

10. Vibrio parahaemolyticus – 1 outbreak with 2 illnesses

Average Annual Foodborne Outbreaks, Bacterial Illnesses 2003-2007:

 1. Salmonella – 129 outbreaks with 3,290 illnesses

 2. Clostridium perfringens – 44 outbreaks with 1,815 illnesses

 3. E. coli (both O157 and non) – 27 outbreaks with 402 illnesses

 4. Campylobacter – 22 outbreaks with 623 illnesses

 5. Bacillus cereus – 18 outbreaks with 138 illnesses

 6. Staphylococcus enterotoxin – 35 outbreaks with 472 illnesses

 7. Shigella – 11 outbreaks with 500 illnesses

 8. Clostridium botulinum – 3 outbreaks with 10 illnesses

 9. Listeria – 2 outbreaks with 13 illnesses

10. Vibrio parahaemolyticus – 2 outbreaks with 109 illnesses

Average Annual Foodborne Virus Outbreaks, Illnesses, 2003-2007

1. Norovirus – 376 outbreaks with 10,534 illnesses

2. Hepatitis A – 5 outbreaks with 234 illnesses

3. Rotavirus – 1 outbreak with 17 illnesses

CDC maps:

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© Food Safety News
  • Doc Mudd

    Indiana is the place to live and eat if these maps are accurate!
    Likewise, the lower Mississippi states are mostly disease-free! Well, maybe not — life expectancy there is short according to this nifty website that drills down to cause by county (including poisonings):
    http://www.worldlifeexpectancy.com/usa/louisiana-life-expectancy
    Hey, wait a minute…the states with active health departments staffed with competent epidemiologists have the most reported cases…Minnesota, Colorado, Oregon, Washington, North Dakota. The exception, of course is Maine, New Hampshire and Vermont, a stalwart backward region where people deliberately project themselves back in time to savor the quaint eccentricities of our forbears, including their foodborne diseases apparently.
    http://www.foodsafetynews.com/2011/03/maine-town-declares-food-sovereignty/
    Indiana…they’ve known this for a long time, I guess
    http://www.youtube.com/watch?v=fZL_tZxyBDo

  • mattj

    In regard to the source of norovirus outbreaks, ill food workers are by far the most common source, but poor handwashing is not the real problem. Because of the insanely low infectious dose, and the insanely high number of virus particles in the stool of infected workers, it is nearly impossible for an ill food worker to wash thoroughly enough to eliminate the risk of disease transmission. Glove use only marginally reduces the risk.
    The key is to keep ill food workers away from work, and if they are afraid of losing income if they stay home, they will show up at work. If a manager does not notice obvious signs of illness, and exclude the worker based on those signs, an outbreak is likely to happen.
    Co-workers will get ill and customers will get ill, but it is highly unlikely that anyone will put the pieces together and identify that an outbreak has occurred. If the outbreak is large enough someone may alert the local health department, but these days the odds of a thorough inspection being conducted are slim.
    All foodborne illnesses are under-diagnosed and under-reported, but norovirus continues to be least of the least.