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Volume 11, Number 1—January 2005

Research

Norovirus and Foodborne Disease, United States, 1991–2000

Marc-Alain Widdowson*Comments to Author , Alana Sulka*, Sandra N. Bulens*†, R. Suzanne Beard*, Sandra S. Chaves†‡, Roberta Hammond§, Ellen D.P. Salehi¶, Ellen Swanson#, Jessica Totaro**, Ray Woron††, Paul S. Mead*, Joseph S. Bresee*, Stephan S. Monroe*, and Roger I. Glass*
Author affiliations: *Centers for Disease Control and Prevention, Atlanta, Georgia, USA; †Atlanta Research and Education Foundation, Atlanta, Georgia, USA; ‡Department of Human Resources, Atlanta, Georgia, USA; §Bureau of Community Environmental Health, Tallahassee, Florida, USA; ¶Ohio Department of Health, Columbus, Ohio, USA; #Department of Health, Minneapolis, Minnesota, USA; **Maryland Department of Health and Mental Hygiene, Baltimore, Maryland, USA; ††New York State Department of Health, Troy, New York, USA

Main Article

Table 2

Selected epidemiologic and clinical features of foodborne outbreaks of gastroenteritis of noroviral, bacterial, and unknown cause, United States, 1998–2000*

Features† Etiology of outbreak
p value‡
Norovirus (N = 136) (%) Bacterial (N = 173)(%) Unknown (N = 907) (%)
No. of persons ill
  <10 22 (16) 65 (38) 544 (60) < 0.001
  >10 114 (84) 108 (62) 363 (40)
Median no. of persons/outbreak (range) 25 persons (2–199) 15 persons (2–736) 7 persons (2–800) 0.001§
Median duration of illness (h)
  <48 111 (82) 70 (40) 763 (85) < 0.001¶
  >48 25 (18) 103 (60) 134 (15)
Median incubation period (h)
  <24 21 (15) 105 (61) 517 (57) < 0.001
  25–48 82 (60) 13 (7) 266 (29)
  >48 33 (25) 55 (32) 124 (14)
% of persons vomiting
  <50 19 (14) 114 (68) 352 (39) < 0.001
  >50 117 (86) 59 (32) 555 (60)
% of persons with fever
  <50 90 (66) 100 (57) 752 (83) < 0.001
  >50 46 (34) 73 (42) 155 (17)

*Data are no. (%), unless otherwise noted.
†No significant differences found in proportions of ill persons with diarrhea or abdominal cramping.
‡Chi-square test for unequal odds unless otherwise noted. p value refers to comparison of norovirus (NoV) outbreaks to both bacterial and unknown outbreaks separately unless otherwise noted.
§Wilcoxon rank sum test comparing median values.
¶Significant association only between NoV and bacterial outbreaks.

Main Article

1Efforts in 1998 to improve outbreak reporting resulted in more outbreaks being retrospectively attributed to this period. The current figures for 1993 to 1997 are 65 (2%) of 3,257 outbreaks attributable to NoV and 67% of unknown etiology.

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