Devamani Carol, Alexander Neal, Chandramohan Daniel, Stenos John, Cameron Mary, Abhilash Kundavaram P P, Mangtani Punam, Blacksell Stuart, Vu Huong Thi Thu, Rose Winsley, Schmidt Wolf-Peter
Department of Child Health 3, Christian Medical College, Vellore, India.
Medical Research Council International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London.
N Engl J Med. 2025 Mar 13;392(11):1089-1099. doi: 10.1056/NEJMoa2408645.
Hospital studies suggest that scrub typhus is a leading cause of severe undifferentiated fever in regions across Asia where the disease is endemic, but the population-based incidence of infection and illness has been little studied.
We conducted a population-based cohort study to assess epidemiologic and clinical characteristics of scrub typhus in 37 villages in Tamil Nadu, India, where the disease is highly endemic. Study participants were visited every 6 to 8 weeks over a period of 2 years; a venous blood sample was obtained from those who had had fever since the last visit. A subcohort of participants underwent blood sampling to estimate the incidence of serologically confirmed infection.
We systematically assessed 32,279 participants from 7619 households for acute febrile illness. During 54,588 person-years of follow-up, we observed 6175 episodes of fever. A blood sample was obtained in 4474 episodes (72.5%), of which 328 (7.3%) met the clinical case definition of scrub typhus (detection of IgM against on enzyme-linked immunosorbent assay [ELISA] or detection of on polymerase-chain-reaction assay). The incidence of clinical infection was 6.0 cases per 1000 person-years (95% confidence interval [CI], 4.8 to 7.5). A total of 71 clinical cases (21.6%) resulted in hospitalization (incidence, 1.3 events per 1000 person-years; 95% CI, 1.0 to 1.7). A total of 29 clinical cases (8.8%) were severe, as indicated by the presence of organ dysfunction or adverse pregnancy outcomes (incidence, 0.5 cases per 1000 person-years; 95% CI, 0.4 to 0.8). Among 2128 participants in the subcohort who provided samples at the beginning and end of a study year, the incidence of seroconversion independent of any symptoms was 81.2 events per 1000 person-years (95% CI, 70.8 to 91.6). The incidence of clinical infection was higher in older age groups than in younger age groups and higher among female participants than among male participants. By contrast, the age-adjusted rate of severe infection was similar among male and female participants. Among 5602 participants assessed at the start of the first year of the study, the seroprevalence of IgG as assessed with ELISA was 42.8% (95% CI, 35.8 to 50.2). IgG seropositivity at the beginning of years 1 or 2 did not protect against clinical illness during the subsequent year but was associated with less severe disease than IgG seronegativity.
We describe the burden of scrub typhus, including the incidence of asymptomatic infection, in a region of Asia where the disease is endemic. (Funded by the U.K. Medical Research Council; ClinicalTrials.gov number, NCT04506944.).
医院研究表明，恙虫病是亚洲疾病流行地区严重未分化发热的主要原因，但基于人群的感染和发病情况研究较少。
我们开展了一项基于人群的队列研究，以评估印度泰米尔纳德邦37个村庄中恙虫病的流行病学和临床特征，该地区恙虫病高度流行。在2年时间里，每6至8周对研究参与者进行一次访视；对自上次访视以来发烧的参与者采集静脉血样。对一部分参与者进行血样采集以估计血清学确诊感染的发生率。
我们系统评估了来自7619户家庭的32279名参与者的急性发热性疾病情况。在54588人年的随访期间，我们观察到6175次发热发作。在4474次发作（72.5%）中采集了血样，其中328次（7.3%）符合恙虫病的临床病例定义（酶联免疫吸附测定[ELISA]检测到抗恙虫病东方体IgM或聚合酶链反应检测到恙虫病东方体）。临床感染发生率为每1000人年6.0例（95%置信区间[CI]，4.8至7.5）。共有71例临床病例（21.6%）导致住院（发生率，每1000人年1.3次；95%CI，1.0至1.7）。共有29例临床病例（8.8%）病情严重，表现为器官功能障碍或不良妊娠结局（发生率，每1000人年0.5例；95%CI，0.4至0.8）。在研究年度开始和结束时提供样本的2128名亚组参与者中，与任何症状无关的血清转化发生率为每1000人年81.2次（95%CI，70.8至91.6）。老年组的临床感染发生率高于年轻组，女性参与者高于男性参与者。相比之下，年龄调整后的严重感染率在男性和女性参与者中相似。在研究第一年开始时评估的5602名参与者中，ELISA检测的IgG血清阳性率为42.8%（95%CI，35.8至50.2）。第1年或第2年初的IgG血清阳性并不能预防随后一年的临床疾病，但与IgG血清阴性相比，疾病严重程度较低。
我们描述了亚洲一个疾病流行地区恙虫病的负担，包括无症状感染的发生率。（由英国医学研究理事会资助；ClinicalTrials.gov编号，NCT04506944。）
