By Dr. Marcia Johnson
January 18, 2001
Click Here To Visit ProMED-mail
(A Program for Monitoring Emerging Diseases by the International Society for Infectious Diseases)
Capital Health Authority (CHA) serves a population of 827 500 in Edmonton, Alberta and surrounding counties. The region has experienced significantly increased rates of invasive meningococcal infection since Dec 1999 associated with a novel serogroup C clone.
The usual incidence of invasive meningococcal disease in the region is 0.5 to 1.5 /100 000 annually. Between Dec 1999 and Dec 2000 inclusive 49 cases of invasive meningococcal disease occurred in CHA (47 in 2000). All cases have been sporadic affecting all parts of the region (although 2 cases in Dec 2000 attended the same rave-like event). Routine public health follow-up including contact tracing and prophylactic antibiotics has occurred with each case. The age groups most affected were 0-4, 15-19 and 20-24 years with rates of 21.6, 27.3 and 10.6 per 100 000 respectively in 2000.
The outbreak was declared in Feb 2000 when the rate in the 15-19 year group reached 10/100 000 in less than 3 months. A mass immunization campaign in Edmonton and surrounding counties using quadrivalent vaccine was undertaken with the cooperation of Alberta Health & Wellness with 168 000 children aged 2 to 19 immunized over a 2-week period in Feb 2000 (an 80% coverage rate).
Cases continued to occur through the spring and summer in all age groups but primarily in those 19 years or less. Vaccine effectiveness rate was 92% between Feb and Oct with 2 cases in immunized children and 6 cases in the population eligible for immunization but unimmunized. The case occurrence accelerated in the Fall of 2000, resulting in a rate of 10.6/100 000 in the 20-24 year age group. In Oct 2000 quadrivalent vaccine was again offered to unimmunized 2-19 year olds and the vaccine campaign was expanded to all 20-24 year olds. A further 60 000 young people were immunized with resulting in a coverage rate of 87% of 2 to 25 year olds.
The Microbiology & Public Health Laboratory (M&PHL) of Alberta (Edmonton) identified a novel strain of _Neisseria meningitidis_ serogroup C through DNA characterization of involved strains by Restriction Fragment Length Polymorphisms using Pulsed Field Gel Electrophoresis (PFGE) as the causative organism in 92.9 percent (39/42) of the recovered serogroup C isolates. PFGE was performed within days of specimen isolation. The lab examined the previous 4 years of meningococcal isolates in Alberta and did not find a similar strain. Isolates from other jurisdictions are currently being tested with no similar isolate being identified to date.
In summary, CHA has experienced an outbreak of meningococcal disease caused by a new serogroup C clone previously unrecognized in this province. The demonstration of the disease consequences of a new clone in a community combined with timely laboratory characterization of different serogroup C clones may prove to be ground breaking in the future management of meningococcal disease.
Marcia M. Johnson, MD, MHSc, FRCPC
Deputy Medical Officer of Health
Capital Health Authority
Edmonton, Alberta, Canada
[Our thanks to Dr. Johnson for this very rapid and thorough reply. According to the original ProMED-mail posting, this outbreak was described as a community-wide person-to-person outbreak and not institutional-based. In the USA, living in college dormitories has been associated with higher risk of disease so that recommendations now include meningococcal vaccination prior to college entry. One wonders if the 20-24 year old population affected by this outbreak were students and would have classified as eligible for vaccination in the USA within the 4 to 5 year protective range of the vaccine. Some questions that remain are: Is the outbreak still ongoing? and, have other provinces in Canada seen the introduction of this novel type of Group C meningococcus? – Mod.MPP]