Molecular Epidemiology of Foodborne Hepatitis A Outbreaks in the United States, 2003
Epidemic Intelligence Service, Epidemiology Program Office and Division of Viral Hepatitis, National Center for Infectious Diseases, Centers for Disease Control and Prevention
Georgia Department of Human Resources, Division of Public Health, Atlanta, Georgia
Tennessee Department of Health, Nashville
Knox County Health Department and East Tennessee Regional Health Office, Tennessee Department of Health, Knoxville
Department of Epidemiology, North Carolina Center for Public Health Preparedness, North Carolina Institute for Public Health, University of North Carolina, Chapel Hill
Pennsylvania Department of Health, Harrisburg
Background.
Molecular epidemiologic investigations can link geographically separate foodborne hepatitis A outbreaks but have not been used while field investigations are in progress. In 2003, outbreaks of foodborne hepatitis A were reported in multiple states.
Methods.
Case-control studies were conducted in 3 states. Hepatitis A virus was sequenced from serologic specimens from individuals associated with outbreaks and from individuals concurrently ill with hepatitis A in nonoutbreak settings in the United States and Mexico.
Results.
Case-control studies in Tennessee (TN), North Carolina (NC), and Georgia (GA) found green onions to be associated with illness among restaurant patrons (TN: odds ratio [OR], 65.5 [95% confidence interval {CI}, 8.9482.5; NC: OR, 2.4 [95% CI, 0.321.9]; GA: OR, 20.9 [95% CI, 3.9110.3]). Viral sequences from TN case patients differed by 2 nt, compared with those from case patients in NC and GA. A third sequence, differing from the TN and GA/NC sequences by 1 nt, was identified among case patients in a subsequent outbreak in Pennsylvania. Each outbreak sequence was identical to 1 sequence isolated from northern Mexican resident(s) with hepatitis A. The sources of green onions served in restaurants in TN and GA were 3 farms in northern Mexico.
Conclusions.
Ongoing viral strain surveillance facilitated the rapid implementation of control measures. Incorporation of molecular epidemiologic methods into routine hepatitis A surveillance would improve the detection of hepatitis A outbreaks and increase our understanding of hepatitis A epidemiology in the United States.
In the United States, hepatitis A virus (HAV) is transmitted primarily by person-to-person contact, but the source of infection for 50% of reported cases is not identified. Foodborne outbreaks are recognized as the source of infection for <5% of reported cases. However, this proportion may be an underestimate, because routine surveillance may not detect cases related to foodborne transmission, and cases may accrue gradually or be dispersed among a number of public health jurisdictions [1].
Incorporation of molecular subtyping methods into surveillance has greatly improved detection of outbreaks and helped to define the epidemiology of other foodborne pathogens [2]. Molecular epidemiologic studies of hepatitis A, which combine HAV sequencing and traditional epidemiologic approaches, have been used to define the distribution of HAV strains and to clarify retrospectively whether case patients who were part of suspected multifocal foodborne outbreaks might be linked [316]. However, viral sequencing is time consuming and not widely available, and it has not previously been integrated into an ongoing epidemiologic investigation of a hepatitis A outbreak.
Hepatitis A is a reportable disease in the United States. In September 2003, hepatitis A outbreaks were reported to the Centers for Disease Control and Prevention (CDC) from state health departments in Tennessee (TN), North Carolina (NC), and Georgia (GA). In each state, preliminary investigations sug
Georgia Department of Human Resources, Division of Public Health, Atlanta, Georgia
Tennessee Department of Health, Nashville
Knox County Health Department and East Tennessee Regional Health Office, Tennessee Department of Health, Knoxville
Department of Epidemiology, North Carolina Center for Public Health Preparedness, North Carolina Institute for Public Health, University of North Carolina, Chapel Hill
Pennsylvania Department of Health, Harrisburg
Background.
Molecular epidemiologic investigations can link geographically separate foodborne hepatitis A outbreaks but have not been used while field investigations are in progress. In 2003, outbreaks of foodborne hepatitis A were reported in multiple states.
Methods.
Case-control studies were conducted in 3 states. Hepatitis A virus was sequenced from serologic specimens from individuals associated with outbreaks and from individuals concurrently ill with hepatitis A in nonoutbreak settings in the United States and Mexico.
Results.
Case-control studies in Tennessee (TN), North Carolina (NC), and Georgia (GA) found green onions to be associated with illness among restaurant patrons (TN: odds ratio [OR], 65.5 [95% confidence interval {CI}, 8.9482.5; NC: OR, 2.4 [95% CI, 0.321.9]; GA: OR, 20.9 [95% CI, 3.9110.3]). Viral sequences from TN case patients differed by 2 nt, compared with those from case patients in NC and GA. A third sequence, differing from the TN and GA/NC sequences by 1 nt, was identified among case patients in a subsequent outbreak in Pennsylvania. Each outbreak sequence was identical to 1 sequence isolated from northern Mexican resident(s) with hepatitis A. The sources of green onions served in restaurants in TN and GA were 3 farms in northern Mexico.
Conclusions.
Ongoing viral strain surveillance facilitated the rapid implementation of control measures. Incorporation of molecular epidemiologic methods into routine hepatitis A surveillance would improve the detection of hepatitis A outbreaks and increase our understanding of hepatitis A epidemiology in the United States.
In the United States, hepatitis A virus (HAV) is transmitted primarily by person-to-person contact, but the source of infection for 50% of reported cases is not identified. Foodborne outbreaks are recognized as the source of infection for <5% of reported cases. However, this proportion may be an underestimate, because routine surveillance may not detect cases related to foodborne transmission, and cases may accrue gradually or be dispersed among a number of public health jurisdictions [1].
Incorporation of molecular subtyping methods into surveillance has greatly improved detection of outbreaks and helped to define the epidemiology of other foodborne pathogens [2]. Molecular epidemiologic studies of hepatitis A, which combine HAV sequencing and traditional epidemiologic approaches, have been used to define the distribution of HAV strains and to clarify retrospectively whether case patients who were part of suspected multifocal foodborne outbreaks might be linked [316]. However, viral sequencing is time consuming and not widely available, and it has not previously been integrated into an ongoing epidemiologic investigation of a hepatitis A outbreak.
Hepatitis A is a reportable disease in the United States. In September 2003, hepatitis A outbreaks were reported to the Centers for Disease Control and Prevention (CDC) from state health departments in Tennessee (TN), North Carolina (NC), and Georgia (GA). In each state, preliminary investigations sug