Novel use of genetic testing methods helped public health officials control and limit the further spread of four outbreaks of foodborne hepatitis A virus in 2003 related to the consumption of green onions, according to a detailed analysis published in the Oct. 15, 2005 issue of the Journal of Infectious Diseases.
The authors of the study, Joseph J. Amon, PhD, MSPH, and colleagues at the Centers for Disease Control and Prevention (CDC), explained that these molecular epidemiologic methods had not previously been used in an ongoing investigation of a hepatitis A virus outbreak. The methods, involving genetic sequencing analysis of virus found in blood samples from infected individuals, have greatly improved understanding of outbreaks of other foodborne pathogens, but are time-consuming and not widely available.
In September 2003, Tennessee, North Carolina, and Georgia reported a total of 422 cases of foodborne hepatitis A virus infection to CDC. Preliminary investigations suggested clustering of reported cases among patrons of three unrelated restaurants. Investigators identified green onions as the likely culprit in the outbreak by interviewing infected and uninfected restaurant patrons. In addition to these standard techniques, the researchers also compared viral RNA sequences from case patients and individuals concurrently ill with hepatitis A virus infection in non-outbreak settings in the United States and Mexico.
Viral RNA sequences from patients in the three states, plus patients involved in a subsequent outbreak in Pennsylvania in October 2003 (the latter recently described in the Sept. 1 issue of the New England Journal of Medicine), were slightly different from each other. The viral sequence from each outbreak, however, was identical to one or more sequences isolated from northern Mexican residents infected with hepatitis A virus. The researchers concluded that the sources of the green onions served in restaurants in Tennessee and Georgia were three farms in northern Mexico.
Amon and colleagues credited the viral sequencing techniques with helping them to identify the relationships between the outbreaks in four separate locations, and to define the scope of the outbreaks quickly. The sequencing allowed them to determine if cases reported in other states were related to the four original outbreaks and provided reassurance that a larger outbreak was not occurring. The molecular epidemiologic methods also enabled public health officials to respond quickly to the later Pennsylvania outbreak. As a result, consumers were warned of the potential risk, and entry of green onions from four Mexican farms into the state was banned.
"This research highlights the role of viral sequence analysis in improving our overall understanding of the roughly 50 percent of hepatitis A cases in the U.S. that are from an unknown source," Amon said. "Just as the E. coli-contaminated beef outbreaks in the early 1990s prompted changes in epidemiological surveillance that have increased our knowledge of foodborne bacteria, the 2003 hepatitis A outbreaks demonstrated the potential for integrated molecular surveillance to provide a better understanding of the epidemiology of hepatitis A and facilitate rapid responses to outbreaks."
Source: Infectious Diseases Society of America
CDC Urges Vigilance: New Recommendations for Monitoring and Testing H5N1 Exposures
July 11th 2025With avian influenza A(H5N1) infections surfacing in both animals and humans, the CDC has issued updated guidance calling for aggressive monitoring and targeted testing to contain the virus and protect public health.
IP LifeLine: Layoffs and the Evolving Job Market Landscape for Infection Preventionists
July 11th 2025Infection preventionists, once hailed as indispensable during the pandemic, now face a sobering reality: budget pressures, hiring freezes, and layoffs are reshaping the field, leaving many IPs worried about their future and questioning their value within health care organizations.
A Helping Hand: Innovative Approaches to Expanding Hand Hygiene Programs in Acute Care Settings
July 9th 2025Who knew candy, UV lights, and a college kid in scrubs could double hand hygiene adherence? A Pennsylvania hospital’s creative shake-up of its infection prevention program shows that sometimes it takes more than soap to get hands clean—and keep them that way.
CDC Urges Vigilance: New Recommendations for Monitoring and Testing H5N1 Exposures
July 11th 2025With avian influenza A(H5N1) infections surfacing in both animals and humans, the CDC has issued updated guidance calling for aggressive monitoring and targeted testing to contain the virus and protect public health.
IP LifeLine: Layoffs and the Evolving Job Market Landscape for Infection Preventionists
July 11th 2025Infection preventionists, once hailed as indispensable during the pandemic, now face a sobering reality: budget pressures, hiring freezes, and layoffs are reshaping the field, leaving many IPs worried about their future and questioning their value within health care organizations.
A Helping Hand: Innovative Approaches to Expanding Hand Hygiene Programs in Acute Care Settings
July 9th 2025Who knew candy, UV lights, and a college kid in scrubs could double hand hygiene adherence? A Pennsylvania hospital’s creative shake-up of its infection prevention program shows that sometimes it takes more than soap to get hands clean—and keep them that way.
2 Commerce Drive
Cranbury, NJ 08512