SARS-CoV-2 傳播：是時候重新考慮公共衛生策略了

資料來源：www.thelancet.com/infection Vol 22 June 2022；財團法人台灣紅絲帶基金會編譯

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  隨著我們進入 COVID-19 大流行的第三個年頭，關於 SARS-CoV-2 傳播動態的許多關鍵問題仍不清楚。在《剌胳針傳染病》中，Cheryl Cohen 及其同事探討了 SARS-CoV-2 家庭傳播所涉及的細微細節。目前的證據支持家庭接觸者之間的傳播是 SARS-CoV-2 傳播的重要驅動因素。家庭環境中的傳播增加可能是由於不使用個人防護設備以及在家庭日常活動中長時間密切接觸。儘管有證據顯示無症狀 COVID-19 患者可以傳播 SARS-CoV-2，但尚不清楚這種傳播的確切程度。

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  Cohen 及其同事對南非 SARS-CoV-2、流感和呼吸道融合病毒之社區負擔、傳播動態和病毒相互作用 (PHIRST-C) 進行的前瞻性家庭世代研究，全面調查了南非的都會和農村之家戶的發生率、再感染和傳播動態。新的研究方法包括密集的症狀篩查、每週兩次的中鼻甲鼻拭子檢測 SARS-CoV-2 和即時定量 RT- PCR（RT-rtPCR；無論症狀如何），每 2 個月進行一次抗 SARS-CoV-2 抗體檢測。研究期間恰逢南非的三個 COVID-19 流行浪潮，這些浪潮是由第一波中的原始野生型病毒株、第二波中的 beta 變異株和第三波中的 delta 變異株所驅動的。

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  該研究報告稱，基於 RT-rtPCR 和血清學結合，1,200 名參與者中有 749 人（62·4%）感染了 SARS-CoV-2，749 人中有 87 人（11·6%）再次感染。與先前對 79 項研究的系統評價（6,616 人中佔 1,287  [19·5%]）相較，無症狀感染的盛行率很高（在有可用數據及 RT-rtPCR 確認事件的662 例中，有 565 例佔了 [85·3%]），即使在年紀較大的參與者（≥19 歲；289 例中有 220 例 [76·1%]）也是如此。與現有證據相比，本研究顯示，家庭累積感染率（從指標病例到易感家庭成員的傳播率）於無症狀指標病例中的（23·9% [731 名易感家庭成員中的 175 名感染]）和有症狀指標病例之間相似 （23·3% [20 of 86]；勝算比 [OR] 1·0 [95% CI 0·5–2·0]）。增加的家庭傳播與 delta 和 beta 變異株有關（與野生型相比，勝算比OR分別為10·4 [4·1-26·7] 和 3·3 [1·4-8·2]）以及和 SARS-指標病例中的 CoV-2 之病毒載量（OR 為5·3 [2·3–12·4]）。

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  此外，HIV 病毒載量未抑制（≥400 copies/mL）的HIV感染者更有可能出現症狀性感染（勝算比OR 3·3 [1·3-8·4]），SARS-CoV-2 的排放時間更長（風險比hazard ratio 0·4 [95% CI 0·3–0·6]），與未感染 HIV 的個體相比。這種不受控制的HIV感染導致免疫抑制的患者其慢性持續性 SARS-CoV-2 感染可能會促進新變異體的出現。因此，迫切需要加強抗反轉錄病毒治療方案，以便優先考慮具有晚期免疫抑制的患者，進行有效的抗反轉錄病毒治療和COVID-19 疫苗接種。

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  我們認為，這項研究在眾多未接種疫苗的人群中家庭傳播 SARS-CoV-2 的流行病學上提供了獨特的見解。與有症狀病例具有相似傳播潛力的無症狀感染的高盛行率，以及需要頻繁檢測以檢測過境式的感染，凸顯了當前篩查和檢測方案的局限性和複雜性。在入口處（例如，餐館、學校、機場）進行症狀和溫度篩檢可能沒有公共衛生預期的感染控制益處。同樣，儘管於入院時嘗試通過症狀和 PCR 篩查來預防院內 COVID-19 傳播，但如果不定期重複檢測，可能會錯過過境式的感染，考慮到 COVID-19 患者可能沒有症狀，並且可能已經發生傳播，即使PCR 測試陰性者。

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  當前的公共衛生方法鼓勵將疫苗接種和非藥物措施相結合，例如戴口罩、保持社交距離、手部衛生和通風策略，以防止 COVID-19 傳播。本研究顯示，南非的 COVID 浪潮可能受年輕人口中之家庭傳播之驅動，凸顯了依靠非藥物介入作為預防和遏制措施的難度。目前，疫苗接種仍然是高危人群的關鍵公共衛生介入措施，可以提供免疫力，從而減輕和限制 COVID-19 造成的嚴重感染、併發症和死亡率。 

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*阿里法·帕克，哈利瑪·達伍德 aparker@sun.ac.za

斯泰倫博斯大學和泰格伯格醫院醫學與健康科學院醫學系普通醫學和傳染病科（AP），開普敦，南非；跨祖魯-納塔爾大學格雷斯醫院和南非愛滋病研究計畫中心傳染病科，德班，南非。

SARS-CoV-2 transmission: time to rethink public health strategy

  As we enter the third year of the COVID-19 pandemic, many key questions about SARS-CoV-2 transmission dynamics remain unclear. In The Lancet Infectious Diseases, Cheryl Cohen and colleagues explore the nuances involved in SARS-CoV-2 household transmission. Current evidence supports transmission between household contacts as a substantial driver of SARS-CoV-2 spread. Increased transmission in household settings is likely to be due to nonuse of personal protective equipment and close prolonged contact during daily activities within the household. Although evidence shows that people with asymptomatic COVID-19 can transmit SARS-CoV-2, the exact extent of this transmission was not known. 

  The prospective household cohort study of SARS-CoV-2, influenza, and respiratory syncytial virus community burden, transmission dynamics, and viral interaction in South Africa (PHIRST-C) by Cohen and colleagues comprehensively investigated the incidence, reinfection, and transmission dynamics within urban and rural households in South Africa. Novel study methodology included intensive symptom screening, midturbinate nasal swabs twice a week for testing of SARS-CoV-2 with real-time RT-PCR (RT-rtPCR; irrespective of symptoms), and anti-SARS-CoV-2 antibody testing every 2 months. The study period coincided with three COVID-19 waves in South Africa, which were driven by original wild-type variant in the first wave, the beta variant in the second wave, and the delta variant in the third wave. 

  The study reports that 749 (62·4%) of 1200 participants were infected with SARS-CoV-2, based on RT-rtPCR and serology combined, and 87 (11·6%) of 749 were reinfected. The prevalence of asymptomatic infection was high (565 [85·3%] of 662 RT-rtPCR-confirmed episodes with available data), even in older participants (≥19 years; 220 [76·1%] of 289), when compared with a previous systematic review of 79 studies (1287 [19·5%] of 6616). In contrast to existing evidence, this study showed that household cumulative infection rate (transmissibility from the index case to susceptible household members) was similar between asymptomatic index cases (23·9% [175 of 731 susceptible household members infected]) and symptomatic index cases (23·3% [20 of 86]; odds ratio [OR] 1·0 [95% CI 0·5–2·0]). Increased household transmission was associated with the delta and beta variants (vs wild-type, OR 10·4 [4·1–26·7] and 3·3 [1·4–8·2], respectively) and increased SARS-CoV-2 viral load in the index case (OR 5·3 [2·3–12·4]). 

  Additionally, people living with HIV who had unsuppressed HIV viral loads (≥400 viral load copies per mL) were more likely to have symptomatic infection (OR 3·3 [1·3–8·4]), with longer shedding of SARS-CoV-2 (hazard ratio 0·4 [95% CI 0·3–0·6]), than HIV-uninfected individuals. This chronic persistent SARS-CoV-2 infection in patients with immunosuppression from uncontrolled HIV infection might promote the emergence of new variants. Therefore, strengthening of antiretroviral treatment programmes is urgently needed, so that patients with advanced immunosuppression are prioritised for effective antiretroviral treatment and COVID-19 vaccination. 

  We think this study provides unique insights into the epidemiology of household transmission of SARS-CoV-2, in a largely unvaccinated population. The high prevalence of asymptomatic infection with similar transmission potential as symptomatic cases, and the need for frequent testing to detect transient infections, highlights the limitations and complexities of current screening and testing protocols. Symptom and temperature screening at entry points (eg, restaurants, schools, airports) might not have the public health infection containment benefit that was expected. Similarly, attempting to prevent nosocomial COVID-19 transmission by symptom and PCR screening on admission to hospital might miss transient infections if tests are not repeated regularly, given that patients with COVID-19 might not have symptoms, and transmission might have already occurred, despite a negative PCR test. 

  Current public health approaches encourage a combination of vaccination and non-pharmacological measures such as wearing a face mask, social distancing, hand sanitation, and ventilation strategies to prevent COVID-19 transmission. This study suggests that the COVID waves in South Africa were potentially driven by household transmission in the young population, highlighting the difficulty in relying on non-pharmacological interventions as prevention and containment measures. At this time, vaccination remains the key public health intervention in highrisk populations that can provide immunity, and thus mitigate and limit severe infections, complications, and mortality from COVID-19. 

*Arifa Parker, Halima Dawood aparker@sun.ac.za 

Divisions of General Medicine and Infectious Diseases, Department of Medicine, Faculty of Medicine and Health Sciences, Stellenbosch University and Tygerberg Hospital, Cape Town, South Africa (AP); Infectious Diseases Unit, Department of Medicine, Greys Hospital and Center for the AIDS Programme of Research in South Africa, University of KwaZulu-Natal, Durban, South Africa (HD)