PERSPECTIVE Table 1. Mean monthly child and adult admissions at the three study hospitals, Kenyaa Kilgoris (1980-1999) Child Adult Child Adult Child Adult Kisii (1987–2000) Tabaka (1981–2000) Jan 96 49 401 239 197 87 Feb 154 81 465 300 201 85 Mar 164 73 515 285 229 97 Apr 127 61 483 267 231 91 May 151 68 632 285 231 93 Mean monthly admissions Jun 242 94 913 357 385 160 Jul 296 112 1,000 387 371 154 Aug 158 60 539 271 230 101 Sep 60 41 336 193 193 87 Oct 34 26 248 190 178 74 Nov 27 16 233 173 158 69 Dec 34 21 281 200 156 71 Total 1,543 702 6,046 3,147 2,760 1,169 aChildren are defined as <15 years of age. Adults are >15 years. consequences of P. falciparum infection. The hypothesis that cross-sectional estimates of the prevalence of P. falciparum communities located at high altitude are prone to unstable, infection in children from birth to 10 years of age in home- infrequent parasite exposure limiting the development of func- steads in Kisii Central during 1990 suggested infection rates tional immunity before adulthood (8,9,30) is, therefore, not between 4.5% and 13% (42). More recently (July 2000), the reflected in our data. prevalence of P. falciparum infection was 10.3% in children Complicated malaria warranting intensive clinical man- from birth to 9 years of age (HL Guyatt, unpub. data). Neither agement is a problem every year at each hospital. Previous the clinical epidemiology nor estimates of the prevalence of Figure 1. Spider plots of adult, child, and total admissions and time series of adult:child ratio for three study hospitals in Kenya. Spider plots of malaria admissions in Kilgoris (A), Kisii (C), and Tabaka (E). The data are monthly averages for the 1980–1999, 1987–2000, and 1981–2000 time periods, respectively. Adult cases (>15 years of age) are shown in blue, child cases (<15 years) are shown in red, and total cases in black. Time series plots of the monthly adult:child ratio data are also shown for Kilgoris (B), Kisii (D), and Tabaka (f) as the continuous black line. The dashed line represents the value of 1 where adult and child admissions are equal, as is to be expected in true epidemic conditions (39–41). The bold line is a 25-point (month) moving average of the adult:child ratio. Emerging Infectious Diseases • Vol. 8, No. 6, June 2002 545