Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
PLoS Negl Trop Dis. 2011 Jan 4;5(1):e935. doi: 10.1371/journal.pntd.0000935.
dengue virus (DENV) was reintroduced into Brazil in 1986 and by 1995 it had spread throughout the country. In 2007 the number of dengue hemorrhagic fever (DHF) cases more than doubled and a shift in the age distribution was reported. While previously the majority of DHF cases occurred among adults, in 2007 53% of cases occurred in children under 15 years old. The reasons for this shift have not been determined.
age stratified cross-sectional seroepidemiologic survey conducted in Recife, Brazil in 2006. Serostatus was determined by ELISA based detection of Dengue IgG. We estimated time-constant and time-varying forces of infection of DENV between 1986 and 2006. We used discrete-time simulation to estimate the accumulation of monotypic and multitypic immunity over time in a population previously completely susceptible to DENV. We projected the age distribution of population immunity to dengue assuming similar hazards of infection in future years. The overall prevalence of DENV IgG was 0.80 (n = 1427). The time-constant force of infection for the period was estimated to be 0.052 (95% CI 0.041, 0.063), corresponding to 5.2% of susceptible individuals becoming infected each year by each serotype. Simulations show that as time since re-emergence of dengue goes by, multitypic immunity accumulates in adults while an increasing proportion of susceptible individuals and those with monotypic immunity are among young age groups. The median age of those monotypically immune can be expected to shift from 24 years, 10 years after introduction, to 13 years, 50 years after introduction. Of those monotypically immune, the proportion under 15 years old shifts from 27% to 58%. These results are consistent with the dengue notification records from the same region since 1995.
assuming that persons who have been monotypically exposed are at highest risk for severe dengue, the shift towards younger patient ages observed in Brazil can be partially explained by the accumulation of multitypic immunity against DENV-1, 2, and 3 in older age groups, 22 years after the re-introduction of these viruses. Serotype specific seroepidemiologic studies are necessary to accurately estimate the serotype specific forces of infection.
登革热病毒（DENV）于 1986 年重新引入巴西，到 1995 年已传播到全国各地。2007 年，登革出血热（DHF）病例数增加了一倍多，年龄分布也发生了变化。以前，大多数 DHF 病例发生在成年人中，但 2007 年，53%的病例发生在 15 岁以下的儿童中。这种转变的原因尚未确定。
2006 年在巴西累西腓进行了分层的横断面血清流行病学调查。通过基于 ELISA 的检测，确定了登革热 IgG 的血清状态。我们估计了 1986 年至 2006 年间 DENV 的时间不变和时变感染力。我们使用离散时间模拟来估计在以前对 DENV 完全易感的人群中，单型和多型免疫随时间的积累。我们假设未来几年感染的风险相似，从而预测人群对登革热的免疫年龄分布。总体 DENV IgG 患病率为 0.80（n=1427）。该时期的时间不变感染力估计为 0.052（95%CI 0.041, 0.063），相当于每年每个血清型有 5.2%的易感个体感染。模拟结果表明，随着登革热再次出现的时间的推移，多型免疫在成年人中积累，而越来越多的易感个体和具有单型免疫的个体出现在年轻年龄组中。预计那些具有单型免疫的人的中位数年龄将从引入后 10 年的 24 岁，变为引入后 50 年的 13 岁。在那些具有单型免疫的人中，15 岁以下的比例从 27%上升到 58%。这些结果与 1995 年以来同一地区的登革热通知记录一致。
假设曾经单型暴露的人患重症登革热的风险最高，那么巴西观察到的患者年龄向年轻方向的转变可以部分解释为，在重新引入这些病毒 22 年后，DENV-1、2 和 3 在年龄较大的人群中积累了多型免疫。进行血清型特异性血清流行病学研究对于准确估计血清型特异性感染力是必要的。
