Emerg Infect Dis. 2024 Sep;30(9):1884-1894. doi: 10.3201/eid3009.240378.
Malaria is increasingly diagnosed in urban centers across the Amazon Basin. In this study, we combined repeated prevalence surveys over a 4-year period of a household-based random sample of 2,774 persons with parasite genotyping to investigate the epidemiology of malaria in Mâncio Lima, the main urban transmission hotspot in Amazonian Brazil. We found that most malarial infections were asymptomatic and undetected by point-of-care microscopy. Our findings indicate that as malaria transmission decreases, the detection threshold of microscopy rises, resulting in more missed infections despite similar parasite densities estimated by molecular methods. We identified genetically highly diverse populations of Plasmodium vivax and P. falciparum in the region; occasional shared lineages between urban and rural residents suggest cross-boundary propagation. The prevalence of low-density and asymptomatic infections poses a significant challenge for routine surveillance and the effectiveness of malaria control and elimination strategies in urbanized areas with readily accessible laboratory facilities.
疟疾在亚马逊盆地的城市中心的诊断率正在不断上升。在这项研究中，我们将基于家庭的随机抽样的 2774 人的寄生虫基因分型的 4 年期间的重复流行率调查结合起来，以调查巴西亚马逊地区曼西尼奥利马的疟疾流行病学。我们发现，大多数疟疾病例是无症状的，无法通过即时检测显微镜检测到。我们的研究结果表明，随着疟疾传播的减少，显微镜的检测阈值升高，尽管通过分子方法估计的寄生虫密度相似，但导致更多的漏诊感染。我们在该地区发现了基因上高度多样化的间日疟原虫和恶性疟原虫种群；城市居民和农村居民之间偶尔存在共享谱系，表明存在跨边界传播。低密度和无症状感染的流行对常规监测以及在具有便捷实验室设施的城市化地区实施疟疾控制和消除策略的有效性构成了重大挑战。
