Seasonality of childhood tuberculosis cases in Kampala, Uganda, 2010-2015

BackgroundSeasonality in tuberculosis (TB) has been described, especially in children. However, few studies have assessed seasonality of TB in the equatorial region, and none in children.ObjectivesTo assess for seasonality of childhood TB cases in Kampala, Uganda, and determine the role of temperature, rainfall patterns, and influenza cases on TB diagnoses.MethodsWe retrospectively analyzed demographic and clinical data of children (under 15 years) diagnosed with TB at a pediatric TB clinic in Kampala, Uganda from 2010 to 2015. We performed decomposition analysis of the monthly case time series to assess seasonality. We compared monthly mean plots and performed Poisson regression to assess any association between TB diagnoses and temperature, rainfall, and influenza.ResultsOf the 713 childhood TB cases diagnosed at the clinic, 609 (85%) were clinically diagnosed and 492 (69%) were pulmonary cases. There were minimal monthly variations in TB cases, with a trough in December and peaks in July and October, but there was no significant seasonality. Temperature variations did not show a clear pattern with TB diagnoses. Rainfall alternated with TB diagnoses in the first half of the year, but then overlapped in the second half and was significantly associated with TB diagnoses. Influenza cases were significantly related to TB diagnoses with (β = 0.05, 95% CI 0.01 to 0.09, p = 0.01) or without (β = 0.06, 95% CI 0.01 to 0.1, p = 0.01) rainfall, and had particular overlap with pulmonary TB cases.ConclusionsSeasonal variations in childhood TB diagnoses were non-significant. Temperature did not have a clear pattern with TB diagnoses, but rainfall and influenza cases correlated with the primarily clinically diagnosed childhood TB cases.

研究背景：结核病（tuberculosis, TB）的季节性特征已有报道，尤以儿童群体为甚。然而，目前针对赤道地区结核病季节性特征的研究尚不多见，针对儿童群体的同类研究更是尚未开展。
研究目的：本研究旨在评估乌干达坎帕拉地区儿童结核病病例的季节性分布特征，并明确气温、降雨模式及流感病例数对结核病诊断的影响。
研究方法：本研究回顾性分析了2010至2015年，乌干达坎帕拉某儿童结核病门诊（pediatric TB clinic）收治的15岁以下确诊结核病儿童的人口统计学与临床资料。研究人员对月度病例时间序列（monthly case time series）开展分解分析（decomposition analysis）以评估其季节性特征；同时对比月度均值分布图表，并实施泊松回归（Poisson regression）分析，以探究结核病诊断数与气温、降雨量及流感病例数之间的关联。
研究结果：本研究共纳入该门诊确诊的713例儿童结核病病例，其中609例（85%）为临床诊断病例，492例（69%）为肺部结核病例。结核病病例数仅存在微弱的月度波动，12月为发病低谷，7月与10月为发病高峰，但未呈现显著的季节性分布特征。气温变化与结核病诊断数未表现出明确的关联模式。上半年降雨量与结核病诊断数呈交替消长趋势，下半年则出现重叠，且降雨量与结核病诊断数存在显著关联。流感病例数与结核病诊断数显著相关：在纳入降雨量因素时，回归系数β=0.05，95%置信区间（95% Confidence Interval, CI）为0.01~0.09，p=0.01；未纳入降雨量因素时，β=0.06，95%置信区间（95% Confidence Interval, CI）为0.01~0.1，p=0.01；且流感病例数与肺部结核病例存在特定的重叠现象。
研究结论：儿童结核病诊断数的季节性变化并不显著。气温与结核病诊断数未呈现明确的关联模式，但降雨量与流感病例数与以临床诊断为主的儿童结核病病例存在显著相关性。