Preventing Foodborne Disease — What Clinicians Can Do
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《新英格兰医药杂志》
The food in the United States is among the safest in the world, but recent outbreaks of hepatitis A remind us that foodborne illness remains an important public health concern. Between September and November 2003, outbreaks of hepatitis A were identified in Tennessee, North Carolina, Georgia, and Pennsylvania. In total, these outbreaks included nearly 1000 cases. The Pennsylvania outbreak among patrons of a single restaurant was the largest outbreak of foodborne hepatitis A ever reported in the United States, with more than 600 infected persons identified to date, including 3 who died. Epidemiologic field investigations of restaurant-associated outbreaks in the four states implicated green onions, rather than infected restaurant workers, as the source of transmission. Trace-back investigations indicate that the green onions served in the restaurants were grown in Mexico. Pending further investigation into the cause of contamination, the Food and Drug Administration (FDA) has advised consumers about the need to cook green onions thoroughly and to ask about the use of green onions in foods prepared outside the home.
Outbreaks of foodborne hepatitis A often attract intense media coverage, but such outbreaks are not common in the United States, where most cases of hepatitis A are acquired through person-to-person transmission in households and extended-family settings or by adults with specific risk factors for infection. On the basis of the epidemiology of hepatitis A, the Advisory Committee on Immunization Practices has made recommendations for the use of hepatitis A vaccine in the United States, which are summarized by Craig and Schaffner in this issue of the Journal (pages 476–481). The national incidence of hepatitis A has declined precipitously with the use of hepatitis A vaccine, from approximately 25,000 to 35,000 reported cases per year in the 1980s and early 1990s to fewer than 10,000 cases in 2002. Despite the recent large outbreaks associated with green onions, the overall rate for 2003 remains very low. However, the full implementation of the current recommendations would result in the vaccination of many millions more people — including people, such as those with chronic liver disease, who are at increased risk for severe hepatitis A. Persons for whom routine vaccination is not currently recommended but who wish to reduce to nearly zero the small risk of transmission of hepatitis A through food or close contact can also be vaccinated. Employers who want to ensure that their workers are protected from hepatitis A and health care plans that want to reduce hepatitis A–related claims can also take advantage of the availability of this safe and effective prevention measure, just as some employers and plans choose to reduce influenza-related illness and costs by providing vaccination against influenza.
Hepatitis A virus is only one of many foodborne pathogens (see Table), and hepatitis A vaccination would prevent a small fraction of the more than 76 million foodborne illnesses and 5000 related deaths that occur annually in the United States. Many of these illnesses are unrecognized or unreported, or their source is never identified, because they are never linked to an outbreak that would prompt an epidemiologic investigation. Laboratory-based surveillance and molecular epidemiology are improving our understanding of the scope and source of foodborne outbreaks by permitting more rapid identification of clusters of cases of illness and links among "sporadic" infections that are not geographically or temporally clustered.
Table. Selected Clinical and Epidemiologic Characteristics of Typical Illnesses Caused by Common Foodborne Pathogens.
However, the identification of outbreaks still depends on alert clinicians who make accurate and timely diagnoses and report cases of foodborne illness immediately to the appropriate public health agency. For some foodborne pathogens, such as Escherichia coli O157:H7, salmonella, and Listeria monocytogenes, subtyping in public health laboratories is critical for the rapid detection and investigation of large outbreaks. Clinical laboratories should rapidly send isolates from patients affected by such outbreaks to the appropriate public health laboratories. The spectrum of agents and clinical presentations is broad and includes diseases that have long incubation periods, such as hepatitis A and listeriosis, and diseases in which gastrointestinal symptoms are not a prominent part of the clinical presentation, such as botulism and ciguatera. Self-limited gastrointestinal infection with E. coli O157:H7 or Campylobacter jejuni may be followed (and obscured) by life-threatening sequelae, such as the hemolytic–uremic syndrome or Guillain–Barré syndrome, respectively. Early diagnosis is also important if the risk of severe complications is to be kept at a minimum. For example, the use of antibiotics should be avoided in patients infected with E. coli O157:H7, and patients who might have hepatitis A should be cautioned to avoid medications that are potentially hepatotoxic, including nonprescription medications such as acetaminophen.
For some persons, certain pathogens confer a greater risk than others of adverse outcomes or death. Patients who are at increased risk for severe hepatitis A can be protected by vaccination. Patients at increased risk for severe infections with other foodborne pathogens should seek advice from health care professionals about how to avoid infection. For example, specific guidelines have been issued by public health agencies and professional associations to help pregnant women reduce their risk of contracting listeriosis by properly cooking or avoiding certain foods. Health care providers should also follow federal, state, and local advisories about other foods that may put their most vulnerable patients at risk.
The year-round availability and increased variety of fresh produce can help to improve the typical U.S. diet, and physicians should continue to promote the health benefits of fresh fruits and vegetables. However, the centralization of food production and widespread distribution also provide opportunities for the broader dissemination of foodborne pathogens. As the per capita consumption of produce has increased, outbreaks associated with contaminated produce have accounted for an increasing proportion of reported outbreaks of foodborne illness. For example, fresh produce has replaced raw shellfish as the most commonly identified source of hepatitis A outbreaks caused by foods that become contaminated before distribution.
The events of September 11, 2001, led Congress to enact the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, which required the FDA to develop four regulations. The first regulation requires domestic and foreign facilities that manufacture, process, pack, or hold food that will be consumed by humans or animals in the United States to register with the FDA. The second regulation requires that the FDA receive prior notification of all food imported or offered for import into the country. The FDA published both of these regulations as interim final rules on October 10, 2003, and it plans to issue the other two regulations by March 2004. One would require persons who manufacture, process, pack, hold, transport, distribute, receive, or import food to keep records that would assist the FDA in identifying the immediate previous sources and immediate subsequent recipients of the food if the FDA had a reasonable belief that an article of food presented a threat of serious adverse health consequences or death to humans or animals. The final regulation will outline the procedures whereby the FDA could detain any article of food for which there is credible evidence of such a threat. The authority to detain food under these criteria became effective with the enactment of the Bioterrorism Act. These regulations will improve our ability to investigate outbreaks that are caused by intentional or unintentional acts or that result from naturally occurring agents.
The identification of steps in the food-production process that can result in contamination and the implementation of measures or protocols that reduce the risk of contamination can reduce the rate of foodborne illness. For example, improving sanitation in the communities where food is grown, harvested, processed, or prepared can reduce the opportunities for food contamination. Outbreaks such as the hepatitis A outbreaks of 2003 highlight gaps in our knowledge about why food contamination occurs and how it can be prevented or minimized. Some foods, such as green onions, seem more prone than others to contamination with certain pathogens, perhaps because they must be handled extensively during harvesting or because of certain characteristics of the plant surfaces. In addition, protocols for the detection of pathogens — especially nonbacterial pathogens — that can be effectively integrated into food-production systems require further development and evaluation.
From farm to table, further improvements in food handling at every stage are critical for ensuring food safety. Health professionals can play an important part in preventing foodborne illness by educating their patients about the risks of foodborne illness, making rapid and appropriate diagnoses, and reporting cases promptly to public health authorities.
Source Information
From the Food and Drug Administration, Center for Food Safety and Applied Nutrition, College Park, Md. (D.W.K.A.); and the Division of Viral Hepatitis, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta (A.E.F.).(David W.K. Acheson, M.D.,)
Outbreaks of foodborne hepatitis A often attract intense media coverage, but such outbreaks are not common in the United States, where most cases of hepatitis A are acquired through person-to-person transmission in households and extended-family settings or by adults with specific risk factors for infection. On the basis of the epidemiology of hepatitis A, the Advisory Committee on Immunization Practices has made recommendations for the use of hepatitis A vaccine in the United States, which are summarized by Craig and Schaffner in this issue of the Journal (pages 476–481). The national incidence of hepatitis A has declined precipitously with the use of hepatitis A vaccine, from approximately 25,000 to 35,000 reported cases per year in the 1980s and early 1990s to fewer than 10,000 cases in 2002. Despite the recent large outbreaks associated with green onions, the overall rate for 2003 remains very low. However, the full implementation of the current recommendations would result in the vaccination of many millions more people — including people, such as those with chronic liver disease, who are at increased risk for severe hepatitis A. Persons for whom routine vaccination is not currently recommended but who wish to reduce to nearly zero the small risk of transmission of hepatitis A through food or close contact can also be vaccinated. Employers who want to ensure that their workers are protected from hepatitis A and health care plans that want to reduce hepatitis A–related claims can also take advantage of the availability of this safe and effective prevention measure, just as some employers and plans choose to reduce influenza-related illness and costs by providing vaccination against influenza.
Hepatitis A virus is only one of many foodborne pathogens (see Table), and hepatitis A vaccination would prevent a small fraction of the more than 76 million foodborne illnesses and 5000 related deaths that occur annually in the United States. Many of these illnesses are unrecognized or unreported, or their source is never identified, because they are never linked to an outbreak that would prompt an epidemiologic investigation. Laboratory-based surveillance and molecular epidemiology are improving our understanding of the scope and source of foodborne outbreaks by permitting more rapid identification of clusters of cases of illness and links among "sporadic" infections that are not geographically or temporally clustered.
Table. Selected Clinical and Epidemiologic Characteristics of Typical Illnesses Caused by Common Foodborne Pathogens.
However, the identification of outbreaks still depends on alert clinicians who make accurate and timely diagnoses and report cases of foodborne illness immediately to the appropriate public health agency. For some foodborne pathogens, such as Escherichia coli O157:H7, salmonella, and Listeria monocytogenes, subtyping in public health laboratories is critical for the rapid detection and investigation of large outbreaks. Clinical laboratories should rapidly send isolates from patients affected by such outbreaks to the appropriate public health laboratories. The spectrum of agents and clinical presentations is broad and includes diseases that have long incubation periods, such as hepatitis A and listeriosis, and diseases in which gastrointestinal symptoms are not a prominent part of the clinical presentation, such as botulism and ciguatera. Self-limited gastrointestinal infection with E. coli O157:H7 or Campylobacter jejuni may be followed (and obscured) by life-threatening sequelae, such as the hemolytic–uremic syndrome or Guillain–Barré syndrome, respectively. Early diagnosis is also important if the risk of severe complications is to be kept at a minimum. For example, the use of antibiotics should be avoided in patients infected with E. coli O157:H7, and patients who might have hepatitis A should be cautioned to avoid medications that are potentially hepatotoxic, including nonprescription medications such as acetaminophen.
For some persons, certain pathogens confer a greater risk than others of adverse outcomes or death. Patients who are at increased risk for severe hepatitis A can be protected by vaccination. Patients at increased risk for severe infections with other foodborne pathogens should seek advice from health care professionals about how to avoid infection. For example, specific guidelines have been issued by public health agencies and professional associations to help pregnant women reduce their risk of contracting listeriosis by properly cooking or avoiding certain foods. Health care providers should also follow federal, state, and local advisories about other foods that may put their most vulnerable patients at risk.
The year-round availability and increased variety of fresh produce can help to improve the typical U.S. diet, and physicians should continue to promote the health benefits of fresh fruits and vegetables. However, the centralization of food production and widespread distribution also provide opportunities for the broader dissemination of foodborne pathogens. As the per capita consumption of produce has increased, outbreaks associated with contaminated produce have accounted for an increasing proportion of reported outbreaks of foodborne illness. For example, fresh produce has replaced raw shellfish as the most commonly identified source of hepatitis A outbreaks caused by foods that become contaminated before distribution.
The events of September 11, 2001, led Congress to enact the Public Health Security and Bioterrorism Preparedness and Response Act of 2002, which required the FDA to develop four regulations. The first regulation requires domestic and foreign facilities that manufacture, process, pack, or hold food that will be consumed by humans or animals in the United States to register with the FDA. The second regulation requires that the FDA receive prior notification of all food imported or offered for import into the country. The FDA published both of these regulations as interim final rules on October 10, 2003, and it plans to issue the other two regulations by March 2004. One would require persons who manufacture, process, pack, hold, transport, distribute, receive, or import food to keep records that would assist the FDA in identifying the immediate previous sources and immediate subsequent recipients of the food if the FDA had a reasonable belief that an article of food presented a threat of serious adverse health consequences or death to humans or animals. The final regulation will outline the procedures whereby the FDA could detain any article of food for which there is credible evidence of such a threat. The authority to detain food under these criteria became effective with the enactment of the Bioterrorism Act. These regulations will improve our ability to investigate outbreaks that are caused by intentional or unintentional acts or that result from naturally occurring agents.
The identification of steps in the food-production process that can result in contamination and the implementation of measures or protocols that reduce the risk of contamination can reduce the rate of foodborne illness. For example, improving sanitation in the communities where food is grown, harvested, processed, or prepared can reduce the opportunities for food contamination. Outbreaks such as the hepatitis A outbreaks of 2003 highlight gaps in our knowledge about why food contamination occurs and how it can be prevented or minimized. Some foods, such as green onions, seem more prone than others to contamination with certain pathogens, perhaps because they must be handled extensively during harvesting or because of certain characteristics of the plant surfaces. In addition, protocols for the detection of pathogens — especially nonbacterial pathogens — that can be effectively integrated into food-production systems require further development and evaluation.
From farm to table, further improvements in food handling at every stage are critical for ensuring food safety. Health professionals can play an important part in preventing foodborne illness by educating their patients about the risks of foodborne illness, making rapid and appropriate diagnoses, and reporting cases promptly to public health authorities.
Source Information
From the Food and Drug Administration, Center for Food Safety and Applied Nutrition, College Park, Md. (D.W.K.A.); and the Division of Viral Hepatitis, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta (A.E.F.).(David W.K. Acheson, M.D.,)