One Way to Protect Yourself From Meningococcal Disease: Be Asocial
abstract & commentary
Synopsis: Among the risk factors for an increased rate of meningococcal carriage were visits to discos, youth clubs, and sport clubs.
Source: Conyn-van Spaendonck MA, et al. Meningococcal carriage in relation to an outbreak of invasive disease due to Neisseria meningitidis serogroup C in the Netherlands. J Infect 1999;39:42-48.
Putten is a small rural dutch town of 22,000. Between May and December 1997, six adolescents and one adult were hospitalized with invasive meningococcal disease (IMD). Most meningococcal infections in North America and Europe are due to serogroup B but the outbreak in Putten was due to serogroup C, serotype 2a, subtype P1.5 (C:2a:P1.5). In fact, during 1997 throughout Holland, there were 19 patients from whom C:2a:P1.5 was isolated.
In January 1998 in the region of Putten, all persons between ages 2 and 20 were vaccinated with meningococcal vaccine, amounting to about 6000 children vaccinated. During this time carriage of meningococci and factors contributing to colonization were also studied. The question was whether there was more colonization in and around Putten than in other Dutch geographic areas.
Oropharyngeal swabs were done on inhabitants of Putten in February 1998 and repeated eight weeks later. All carriers were matched with two controls.
There were 411 persons from Putten included in the study who responded to a questionnaire. Of the 411, 51 carried N. meningitidis (12.4%). Two of seven group C strains were C:2a:P1.5. Adolescents were more likely to be colonized. In the "control" town of Wenlo, 374 persons were studied with 68 found to carry N. meningitidis (18.2%). In Venlo, the highest prevalence was among 16-20 year olds.
In the follow-up study, six of 55 known noncarriers became colonized for an acquisition rate of 11% (1 was serogroup C:2a:P1.5). Of seven known carriers six were restudied, two of whom carried C:2a:P1.5. Only one continued to carry the C:2a:P1.5 strain.
Risk factors for carriers included increasing family size, "discotheque" visits, and visits to youth clubs and sport clubs. Visits to a disco in the previous eight weeks had an OR of 2.3. Persons aged 8-13 had an increased carriage rate three times that of younger children and a five times higher carriage rate than older persons. The use of antimicrobials during the previous eight weeks lowered the risk of carriage to 30%. Swimming, on the other hand, was associated with a decreased risk.
Comment by joseph f. john, md
This study confirms that there are geographic differences in carriage of pathogenic bacteria, even among small towns in small countries. In the case of this study, we see that strains of meningococci capable of producing invasive disease do enter and persist in small town populations, even though their carriage rates may be lower than nonpathogenic meningococci. Some persons colonized with invasive strains may carry the same strains for weeks, but this study was not large enough to make broader generalizations.
The risk factors from this study were interesting. It has been known for years that the close contact in military barracks or within the family unit constitute risk factors for acquisition. A more interesting evolving risk factor is exposure during leisure time. U.S. studies have shown that meningococcal carriage is associated with binge drinking and going to college bars. This Dutch study showed the disco experience to be associated with carriage, although Conyn-van Spaendonck and colleagues failed to study alcohol consumption during disco dancing.
The finding of a carriage rate of 30-40% in persons aged 16-19 in this study affects the current recommendations about meningococcal vaccination in persons attending college in the United States. There has been some impetus to vaccinate college students. Phone lines were abuzz late this summer with questions about whether Billy should get his meningococcal vaccine before he headed off for his freshman year at the college of his choice. But should we limit protection to college-aged persons? This Dutch study would call into question additional risk for carriage of students of high school age. Before jumping into that quagmire, we clearly require more studies like this Dutch study and new studies, using a similar format, should be extended to much larger populations.
What risks are not associated with carriage of Neisseria meningitidis?
a. binge drinking
b. disco club activity
c. swimming
d. close family association
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