An attempt at an epidemiological explanation - Epib.nl

Chapter 2Table 2. An nual number of meningococcal isolates, agc.spccific and QvcraU incidence ratcs ofmeningococcal disease (per 100,000 subjects) in the Netherlands, 1980· 1990Age-specific incidence (y)No. ofOverallYear isolates 0-4 5-9 10-14 15-19 20-24 ",25 incidence1980 209 11.8 1.7 1.7 1.8 0.2 0.4 1.51981 230 11.9 2.9 1.8 1.8 0.7 0.4 1.61982 162 8.9 2.0 1.3 1.3 1.1 0.2 1.11983 183 10.2 1.5 1.5 1.8 0.3 0.4 1.31984 196 11.3 2.5 1.6 1.9 0.7 0.3 1.41985 254 13.2 3.9 1.6 3.3 0.9 0.4 1.81986 357 16.4 5.5 3.7 4.7 1.4 0.5 2.51987 337 16.0 6.6 2.9 4.2 1.4 0.4 2.31988 383 17.2 6.8 1.8 6.2 1.4 0.6 2.61989 520 23.4 9.1 6.3 6.7 2.1 0.7 3.51990 523 22.8 6.8 7.4 8.0 1.7 0.7 3.5In the 1980s the annual incidence of MD has increased from 1.1 cases per 100,000persons (162 cases) in 1982 to 3.5 per 100,000 persons (523 cases) in 1990 (Table 2).11tis increase was caused by a rise in the number of isolates of both serogroup B,which was the predominant serogroup in the Netherlands, and serogroup C (Table 3)_The number of serogroup A isolates decreased from 1980 to 1983 and accounted foronly 2% of the total number of meningococcal isolates in 1990.Table 3. Meningococcal disease in the Netherlands, 1980· 1990: distribution o f serogroups (in absolutenumbers) and proportion of strains isolated from blood alone (blood-strains) per yearData for indicated yearVari able 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990SerogroupA 59 48 21 9 6 8 6 8 14 12 11B 99 117 98 121 147 192 275 263 278 401 385C 45 60 36 45 40 49 64 56 81 94 115X 0 1 I 2 0 0 4 0 1 1 1Y 1 I I 2 I 2 5 4 2 4 3Z 0 0 0 1 0 0 0 1 1 1 129E 0 0 I 0 0 0 0 0 0 1 0W-135 5 1 4 3 1 3 3 3 6 3 3Nongroupable 0 2 0 0 1 0 0 2 0 3 4Total 209 230 162 183 196 254 357 337 383 520 523Proportion ofblood-strains 8% 10% 12% 15% 13% 12% 13% 17% 14% 19% 21%22