I was watching a King 5 TV report this evening regarding the ongoing E. coli outbreak north of Seattle that has sickened dozens – some who never even attended the event (secondary cases). The tragedy reminded me that the Centers for Disease Control and Prevention (CDC), in its journal “Emerging Infectious Diseases,” published a study recently on “secondary” E. coli O157:H7 infections. A “secondary” infection is roughly defined as a person who is part of an outbreak that did not consume the implicated food or was exposed to an E. coli source, but rather fell ill through exposure to an ill person who did consume the food or was exposed to E. coli.
Lead author Mary E. Locking and her colleagues reviewed E. coli outbreaks in Scotland from 1999-2008. The authors found that 11% of the cases in the outbreaks they reviewed were secondary. It was also reported that factors that increased the likelihood of secondary transmission included the “presence of siblings, young age of persons with primary or potential secondary cases, and waterborne compared with foodborne transmission in outbreaks.”
Person-to-person transmission in E. coli O157:H7 outbreaks has been documented in the past. These reports include:
- K. Ludwig, “Outbreak of Escherichia coli 0157:H7 Infection in a Large Family,” Eur. J. Clin. Microb. Infect. Dis. Vol. 16, at 238-41 (1997);
- P. Rowe, “Diarrhea in Close Contacts as a Risk Factor for Childhood Hemolytic Uremic Syndrome,” Epidem. Infect. 110:9-16 (1993).
- E. Belongia, et al., “Transmission of Escherichia coli 0157:H7 Infection in Minnesota Child-Care Facilities,” JAMA, at 887 (Feb. 17, 1993) (describing the inevitable spread of illness from primary to secondary cases).
Secondary cases have been recognized in the legal context as well. Nearly a decade ago, MarlerClark took the claim of a young girl who was a secondary case in an outbreak to trial, and then up on appeal. The Court upheld the girl’s claim. Almquist et al. v. Finley Sch. Dist., 57 P. 3d 1191 (Wash. App. 2002) Cert Denied 75 P.3d 968 (2003).