ATLANTA — Viruses surpassed bacteria as the pathogen group responsible for the most foodborne disease outbreaks in the United States in 2004, Rachel Yelk Woodruff reported in a poster at the International Conference on Emerging Infectious Diseases.
She and her colleagues at the Centers for Disease Control and Prevention in Atlanta reviewed data on 9,034 foodborne outbreaks collected through the Foodborne Outbreak Reporting System from 1998 to 2004.
Overall, the number of foodborne disease outbreaks remained stable during the study period, but the median number of illnesses per outbreak increased steadily, from a median of six illnesses per outbreak during 1998–2000, to seven illnesses per outbreak during 2001–2003, and eight illnesses per outbreak in 2004, Ms. Woodruff and her associates said.
In 2004, viral pathogens caused more outbreaks than did bacterial pathogens (249 vs. 208). In contrast, foodborne disease outbreaks caused by bacterial pathogens outnumbered those caused by viral pathogens during 1998–2003.
However, the median number of illnesses per viral outbreak decreased from 32 in 1998 to 22 in 2004, while the median number of illnesses per bacterial outbreak was fairly stable: 12 in 1998 and 11 in 2004.
Salmonella was the predominant bacteria, accounting for 9%–12% of all bacterial outbreaks. Shiga toxin-producing Escherichia coli (STEC) was the second most common, accounting for 1%–2% of all reported outbreaks. The total number of Salmonella outbreaks did not change significantly from 1998 to 2004 (125 vs. 117).
The number of STEC outbreaks decreased from 26 to 16, and the number of outbreaks of unknown origin decreased from 946 in 1998 to 801 in 2004.