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An outbreak of foodborne disease is defined as the occurrence of two or more cases of a similar illness resulting from ingestion of a common food (1). It is a global health problem that is harmful to humans. Foodborne diseases encompass a wide spectrum of illnesses, including infectious diseases caused by microorganisms and toxic diseases mainly caused by chemical and toxic agents. The World Health Organization estimated that 600 million foodborne diseases occurred globally in 2010, causing 420,000 deaths (2). The US CDC estimated that 48 million foodborne diseases (1 in 6 Americans) occur each year in the USA, resulting in 12,800 hospitalizations and 3,000 deaths (3). In the Western Pacific Region, including China, 125 million people get sick and more than 50,000 die every year due to foodborne diseases (4). Foodborne diseases bring huge economic burdens to human beings. According to the requirements of Food Safety Law of the People’s Republic of China, the National Foodborne Disease Outbreaks Surveillance System was established to continuously and systematically collect data on foodborne disease outbreaks in 2010.
Therefore, the objectives of this study were to characterize the epidemiological status of foodborne diseases in China and to analyze the distribution of high-risk foods and pathogenic factors to provide technical support for food safety risk assessment, formulation and revision of standards, and risk management.
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The study obtained data on foodborne disease cases reported through the National Foodborne Disease Outbreaks Surveillance System from January 1, 2020 to December 31, 2020. Data were collected from 30 of 31provincial-level administrative divisions (PLADs) in the mainland of China, excluding Xizang (Tibet) Autonomous Region. Data requested for each outbreak report included the individual CDC reporting the outbreak, date of occurrence, number of illnesses, hospitalizations, and deaths, etiology, implicated food(s) and setting. All variable values were reported as counts or proportions (%). The number and proportion of outbreaks, illnesses, and deaths by etiology, setting, and food categories were calculated. The statistical analysis was performed using SPSS (version 21.0, IBM Corp, Chicago, USA).
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Most outbreaks (97.5%), illnesses (98.0%), and deaths (99.1%) were linked to households and catering service locations. Households and catering service locations were the most common settings of reported outbreaks. In 2020, the highest number of outbreaks occurred in households (4,140), followed by catering service locations (2,719), and school campuses (27). Most illnesses (59.9%) were reported in catering service locations, followed by households (37.6%), and 0.5% in campuses. Within catering service locations, street stalls accounted for the largest proportion (26.2%) of outbreaks, and school canteens accounted for the largest proportion (13.6%) of illnesses. However, households had the most deaths, accounting for 89.5% of all deaths (Table 1); poisonous mushrooms (79 deaths), aconite (10 deaths), bongkrek acid (11 deaths), and methanol (8 deaths) were the most common causes of deaths, accounting for 84.4% of total deaths in private home settings.
Setting Outbreaks Illnesses Deaths Fatality rate*
(%)Number Proportion
(%)Number Proportion
(%)Number Proportion
(%)Household 4,140 58.5 14,066 37.6 128 89.5 0.9 Catering Service Places 2,719 38.4 22,432 59.9 15 10.5 0.1 Street stall 712 10.1 2,659 7.1 3 2.1 0.1 Hotel restaurant 508 7.2 4,184 11.2 5 3.5 0.1 Staff canteen 371 5.3 3,607 9.6 1 0.7 0.0 School canteen 310 4.4 5,081 13.6 0 0.0 0.0 Bistro 291 4.1 1,473 3.9 3 2.1 0.2 Fast food restaurant 240 3.4 1,171 3.1 0 0.0 0.0 Rural banquet 130 1.8 2,165 5.8 3 2.1 0.1 Home delivery of meal 110 1.6 1,807 4.8 0 0.0 0.0 Other 47 0.7 285 0.8 0 0.0 0.0 Campus 27 0.4 196 0.5 0 0.0 0.0 Other location 187 2.6 760 2.0 0 0.0 0.0 Total 7,073 100.0 37,454 100.0 143 100.0 0.4 * Fatality rate=number of deaths / number of illnesses. Table 1. Number and proportion of foodborne disease outbreaks, illnesses, and deaths by setting in China, 2020.
In 2020, there were 4,662 outbreaks with confirmed etiology. Poisonous mushrooms were the most common cause of outbreaks and deaths, accounting for 58.0% of outbreaks and 57.6% of deaths; bacterial pathogens were the most common cause of illnesses (41.7%); in poisonous animals and plants and their toxins, undercooked Phaseolus was the most common cause leading to the largest proportion of outbreaks (31.2%) and illnesses (33.3%); aconite had the most deaths, accounting for 57.1%. Within microbial pathogens, Salmonella (286 outbreaks and 3,446 illnesses) was the most common bacterial pathogen associated with outbreaks and illnesses, followed by Vibrio parahaemolyticus (128 outbreaks and 1,848 illnesses), and Staphylococcus aureus (75 outbreaks and 954 illnesses). Bongkrek acid accounted for the largest proportions (75.0%) of deaths and the largest fatality rate (52.2%). Among the chemical agents, nitrite was the most common pathogenic factor associated with outbreaks (49.1%) and illnesses (49.6%), followed by pesticide (32.5% outbreaks and 27.7% illnesses); methanol had the highest death and fatality rates at 63.6% and 25.0%, respectively, followed by nitrite at 22.7% and 1.1%, respectively (Table 2).
Etiology Outbreaks Illnesses Deaths Fatality
rate* (%)Number Proportion (%) Number Proportion(%) Number Proportion(%) Poisonous mushrooms 2,705 38.2 9,111 24.3 80 55.9 0.9 Plant and animal toxicants 1,020 14.4 4,584 12.2 21 14.7 0.5 Undercooked Phaseolus* 318 4.5 1,526 4.1 0 0.0 0.0 Coriaria sinica 111 1.6 354 1.0 0 0.0 0.0 Potherb 93 1.3 355 1.0 1 0.7 0.3 Aconite 84 1.2 337 1.0 12 8.4 3.6 Bitter bottle gourd 48 0.7 381 1.0 0 0.0 0.0 Tungoil or seed 46 0.7 238 0.6 0 0.0 0.0 Hyoscyamine 33 0.5 183 0.5 1 0.7 0.6 Herb-medicine 27 0.4 110 0.3 0 0.0 0.0 Elephant’s-ear 24 0.3 86 0.2 0 0.0 0.0 Sproutedpotato/solanine 17 0.2 97 0.3 2 1.4 2.1 Colchicin 12 0.2 78 0.2 0 0.0 0.0 Gelsemine 11 0.2 64 0.2 3 2.1 4.7 Castor bean 10 0.1 58 0.2 0 0.0 0.0 Pokeberry root 10 0.1 42 0.1 1 0.7 2.4 Sago seed 10 0.1 36 0.1 0 0.0 0.0 Barbados nut 9 0.1 41 0.1 0 0.0 0.0 Undercooked soymilk/Trypsin inhibitor † 3 0.0 18 0.1 0 0.0 0.0 Other plants toxicants§ 83 1.2 285 0.8 0 0.0 0.0 Fish roe 19 0.3 51 0.1 0 0.0 0.0 Tetrodotoxin 15 0.2 53 0.1 1 0.7 1.9 Pupae 13 0.2 60 0.2 0 0.0 0.0 langoustine 10 0.1 25 0.1 0 0.0 0.0 Other animal toxicants** 14 0.2 106 0.3 0 0.0 0.0 Bacterial 766 10.8 10,483 28.0 16 11.2 0.2 Salmonella 286 4.0 3,446 9.2 4 2.8 0.1 Vibrio parahaemolyticus 128 1.8 1,848 4.9 0 0.0 0.0 Staphylococcus aureus 75 1.1 954 2.6 0 0.0 0.0 Escherichia coli 54 0.8 1,520 4.1 0 0.0 0.0 Bacillus cereus 50 0.7 620 1.7 0 0.0 0.0 Bacillus proteus 10 0.1 149 0.4 0 0.0 0.0 Clostridium perfringens 5 0.1 287 0.8 0 0.0 0.0 Bongkrek acid†† 5 0.1 23 0.1 12 8.4 52.2 Campylobacter jejuni 3 0.0 133 0.4 0 0.0 0.0 Clostridium botulinum 3 0.0 10 0.0 0 0.0 0.0 Listeria monocytogenes 1 0.0 28 0.1 0 0.0 0.0 Others 108 1.5 807 2.2 0 0.0 0.0 2 or more pathogens 12 0.2 224 0.6 0 0.0 0.0 Norovirus 26 0.4 434 1.2 0 0.0 0.0 Chemical agents 163 2.3 922 2.5 22 15.4 2.4 Nitrite 80 1.1 457 1.2 5 3.5 1.1 Pesticide§§ 53 0.8 255 0.7 2 1.4 0.8 Prohibited drugs 10 0.1 115 0.3 1 0.7 0.9 Methanol 9 0.1 56 0.2 14 9.8 25.0 Other chemical pollutants*** 11 0.2 39 0.1 0 0.0 0.0 Fungi 7 0.1 27 0.1 0 0.0 0.0 Parasitic 1 0.0 4 0.0 0 0.0 0.0 Unknown etiology 2,411 34.1 12,323 32.9 4 2.8 0.0 Total 7,073 100.0 37,454 100.0 143 100.0 0.4 * Refers to uncooked Phaseolus beans.
† Contained in uncooked soy milk.
§ Including wild flowers, hellebore, wild ginseng, pollen, daffodils, and wild fruits, etc. Including bee pupae and silkworm pupae.
** Including dog liver, insects, fish gall, toads and ants, etc.
†† Including Shigella, Aeromonas, Enterobacter cloacae, Citrobacter flaudus, Schneider, and Enterococcus, etc.
§§ Including Carbamates, organophosphates, pyrethroids, paraquat, bromfamethamine and bromadiolone, etc. Including clenbuterol hydrochloride, xylazine, and tetramine.
*** Including lead, engine oil, desiccant, chlorine dioxide, and detergent, etc.Table 2. Number and proportion of foodborne disease outbreaks, illnesses, and deaths by etiology in China, 2020.
In 2020, outbreaks that occurred at households (7,073) had surpassed those of catering service units (5,652), and outbreaks (485) and outbreak-associated illnesses (6,661) caused by Salmonella surpassed those of Vibrio parahaemolyticus. Foodborne disease illnesses occurred in school canteens (5,081).
The top 10 pathogen-food category pairs resulting in outbreaks, outbreak-associated illnesses, and deaths were analyzed. Salmonella in eggs had the highest occurrence, accounting for 32.8% (75/229) of outbreaks, followed by Salmonella in sauce-marinated meat (Table 3). Salmonella in sauce-marinated meat had the highest proportion (21.7%) of illnesses and 23.2% of hospitalizations, followed by Salmonella in eggs.
Etiology Food category No. outbreaks Proportion (%) Salmonella Egg 75 32.8 Salmonella Sauce-marinated meat 44
19.2Salmonella Pastry 28 12.2 Bacillus cereus Rice flour 22 9.6 Vibrio prahaemolyticus Sauce-marinated meat 17 7.4 Salmonella Livestock meat 13 5.7 Vibrio parahaemolyticus Crustaceans 11 4.8 Escherichia coli Sauce-marinated meat 10
4.4Staphylococcalaureus enterotoxins
Pastry
9
3.9Salmonella Poultry 6 100.0 Total 229 32.8 Table 3. Top 10 number and proportion of most common confirmed pathogen-food category pairs resulting in outbreak in China, 2020.
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Influenced by the coronavirus disease 2019 (COVID-19) pandemic, epidemiological characteristics of foodborne diseases in China had changed greatly in 2020.
For the first time in the past 5 years, outbreaks that occurred in private homes had surpassed that of catering service units in 2020 (5). The local residents in mountainous areas of southwest and central China tended to pick mushrooms and poisonous plants frequently in the wild (6). Continued and targeted health education programs should caution against picking wild mushrooms and toxic wild fruits. Eating habits with regional characteristics should be further emphasized and intervention measures should be taken to reduce the occurrence of poisonings.
The study showed that poisonous mushrooms caused the most deaths, the same as previous studies (5). They were mainly caused by wild mushrooms collected by households (97.5%). This was consistent with the research results of Ren et al. (6). Residents picking and eating mushrooms could not distinguish between poisonous mushrooms from non-toxic mushrooms, and the rate of timely treatment after poisoning was low and increased the risk of death. Health education targeted for specific groups in rural areas is also essential to reduce mushroom poisonings.
Outbreaks and illnesses caused by Salmonella surpassed that of Vibrio parahaemolyticus, becoming the first pathogenic bacteria of bacterial foodborne diseases. This analysis on pathogen and food pairs in China showed that Salmonella outbreaks were most often linked to eggs, sauce-marinated meat products. Data showed that Salmonella was responsible for the largest number of outbreaks, hospitalizations, and deaths among meats and eggs; this was consistent with the result from the EU: Salmonella accounted for 36.8% of deaths in “eggs and egg products” (7). For Salmonella outbreaks, most outbreak-associated cases in the US were associated with seeded vegetables, eggs, poultry, beef, and pork, which differed from China (8). Pathogenic microbial contamination was still the main pathogenic factor of foodborne diseases in China and an important food safety issue that should not be ignored. Hygiene guidance and education should be done to reduce the burden of foodborne diseases caused by microbial factors.
Therefore, continued surveillance for foodborne disease outbreaks is important to understand changes in the foods, settings, and pathogens associated with illness (9). In order to reduce public health risks, more measures were adopted to enhance awareness of reporting, improve trace-back technology to achieve early detection, early warning, and early control of food safety risks.
This study was subject to at least two limitations. First of all, for many reported outbreaks, information on certain aspects of the outbreaks was missing or incomplete, so the conclusions might not be representative of unknown aetiologies or food categories. Second, reported foodborne disease outbreaks can’t represent all actual occurred outbreaks, since underreporting existed for various reasons, such as administrative intervention, insufficient ability of outbreak investigation, etc.
Not all the National Foodborne Disease Outbreaks Surveillance System recorded with the epidemiological information in 2020. Like most countries, there are also cases of under-report, and incomplete information.
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Members in all participating CDCs.
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No reported conflicts.
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