Epidemic serogroup B meningococcal disease in Oregon: the evolving epidemiology of the ET-5 strain

JAMA. 1999 Apr 28;281(16):1493-7. doi: 10.1001/jama.281.16.1493.


Context: In 1993, Oregon's incidence of serogroup B meningococcal disease began to rise because of a highly clonal group of strains designated enzyme type 5 (ET-5), the first such increase observed in the United States.

Objective: To evaluate the impact that the ET-5 strain has had on the epidemiology of meningococcal disease in Oregon.

Design and setting: Epidemiologic analysis of surveillance data on Oregon meningococcal disease cases from 1987 through 1996 and multilocus enzyme electrophoresis typing of serogroup B isolates from June 1993 through April 1995 and from April through June 1996.

Patients: A total of 836 persons with invasive meningococcal disease.

Main outcome measures: Disease frequency and clonality of strains.

Results: Serogroup B disease incidence rates more than doubled from the preepidemic period in 1987-1992 (1.0 case per 100000 population) to the recent epidemic period in 1995-1996 (2.2 cases per 100000). The age-specific incidence rate of serogroup B disease among those 15 through 19 years old increased 13-fold between the preepidemic period (0.5 case per 100000) and 1995-1996 (6.4 cases per 100000). However, the proportion of cases with meningococcemia and the case-fatality rate did not change. Of 99 Neisseria meningitidis isolates obtained from 1993-1995, 88 (89%) belonged to the ET-5 complex. Of these, 69 (78%) were a single clone, designated 301. Of 20 serogroup B isolates from 1996, 18 (90%) belonged to the ET-5 complex; 17 (94%) were the 301 clone.

Conclusion: Serogroup B meningococcal disease incidence continues at high levels in Oregon with increasing predominance of the ET-5 clonal strains.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Child
  • Child, Preschool
  • Disease Outbreaks*
  • Female
  • Humans
  • Incidence
  • Infant
  • Male
  • Meningococcal Infections / epidemiology*
  • Meningococcal Infections / microbiology
  • Middle Aged
  • Neisseria meningitidis / classification*
  • Neisseria meningitidis / isolation & purification
  • Oregon / epidemiology
  • Serotyping