Zambia Ministry of Health, Lusaka, Zambia; University Teaching Hospital, Lusaka, Zambia; Levy Mwanawasa Medical University, Lusaka, Zambia; Vanderbilt Medical University, Nashville, TN, USA; School of Medicine, University of Zambia, Lusaka, Zambia.
Centers for Disease Control and Prevention, Lusaka, Zambia.
Lancet Glob Health. 2021 Jun;9(6):e773-e781. doi: 10.1016/S2214-109X(21)00053-X. Epub 2021 Mar 9.
Between March and December, 2020, more than 20 000 laboratory-confirmed cases of SARS-CoV-2 infection were reported in Zambia. However, the number of SARS-CoV-2 infections is likely to be higher than the confirmed case counts because many infected people have mild or no symptoms, and limitations exist with regard to testing capacity and surveillance systems in Zambia. We aimed to estimate SARS-CoV-2 prevalence in six districts of Zambia in July, 2020, using a population-based household survey.
Between July 4 and July 27, 2020, we did a cross-sectional cluster-sample survey of households in six districts of Zambia. Within each district, 16 standardised enumeration areas were randomly selected as primary sampling units using probability proportional to size. 20 households from each standardised enumeration area were selected using simple random sampling. All members of selected households were eligible to participate. Consenting participants completed a questionnaire and were tested for SARS-CoV-2 infection using real-time PCR (rtPCR) and anti-SARS-CoV-2 antibodies using ELISA. Prevalence estimates, adjusted for the survey design, were calculated for each diagnostic test separately, and combined. We applied the prevalence estimates to census population projections for each district to derive the estimated number of SARS-CoV-2 infections.
Overall, 4258 people from 1866 households participated in the study. The median age of participants was 18·2 years (IQR 7·7-31·4) and 50·6% of participants were female. SARS-CoV-2 prevalence for the combined measure was 10·6% (95% CI 7·3-13·9). The rtPCR-positive prevalence was 7·6% (4·7-10·6) and ELISA-positive prevalence was 2·1% (1·1-3·1). An estimated 454 708 SARS-CoV-2 infections (95% CI 312 705-596 713) occurred in the six districts between March and July, 2020, compared with 4917 laboratory-confirmed cases reported in official statistics from the Zambia National Public Health Institute.
The estimated number of SARS-CoV-2 infections was much higher than the number of reported cases in six districts in Zambia. The high rtPCR-positive SARS-CoV-2 prevalence was consistent with observed community transmission during the study period. The low ELISA-positive SARS-CoV-2 prevalence might be associated with mitigation measures instituted after initial cases were reported in March, 2020. Zambia should monitor patterns of SARS-CoV-2 prevalence and promote measures that can reduce transmission.
US Centers for Disease Control and Prevention.
2020 年 3 月至 12 月期间，赞比亚报告了超过 2 万例经实验室确认的 SARS-CoV-2 感染病例。然而，由于许多感染者症状轻微或无症状，以及赞比亚在检测能力和监测系统方面存在限制，SARS-CoV-2 感染的实际人数可能高于确诊病例数。我们旨在 2020 年 7 月使用基于人群的家庭调查，估计赞比亚六个地区的 SARS-CoV-2 流行率。
2020 年 7 月 4 日至 7 月 27 日，我们对赞比亚六个地区的家庭进行了横断面聚类抽样调查。在每个地区，使用与大小成比例的概率随机选择 16 个标准化的人口普查区作为初级抽样单位。从每个标准化的人口普查区中选择 20 户家庭，采用简单随机抽样。所有被选中家庭的成员都有资格参加。同意参加的参与者完成了一份调查问卷，并使用实时 PCR（rtPCR）和 ELISA 对 SARS-CoV-2 感染进行了检测。单独计算并结合了每种诊断检测的校正后患病率估计值。我们将这些患病率估计值应用于每个地区的人口普查预测，以得出 SARS-CoV-2 感染的估计数量。
总体而言，来自 1866 户家庭的 4258 人参加了研究。参与者的中位年龄为 18.2 岁（IQR 7.7-31.4），其中 50.6%为女性。综合指标的 SARS-CoV-2 患病率为 10.6%（95%CI 7.3-13.9）。rtPCR 阳性患病率为 7.6%（4.7-10.6），ELISA 阳性患病率为 2.1%（1.1-3.1）。估计在 2020 年 3 月至 7 月期间，六个地区发生了 454708 例 SARS-CoV-2 感染（95%CI 312705-596713），而赞比亚国家公共卫生研究所官方统计数据报告了 4917 例实验室确诊病例。
估计的 SARS-CoV-2 感染人数远高于赞比亚六个地区报告的病例数。高 rtPCR 阳性 SARS-CoV-2 患病率与研究期间观察到的社区传播一致。低 ELISA 阳性 SARS-CoV-2 患病率可能与 2020 年 3 月首次报告病例后实施的缓解措施有关。赞比亚应监测 SARS-CoV-2 流行率的模式，并促进可降低传播的措施。
美国疾病控制与预防中心。
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