Division of Infection Control and Environmental Health, Norwegian Institute of Public Health, Oslo, Norway.
SAMBA, Norwegian Computing Center, Oslo, Norway.
Infect Dis (Lond). 2022 Jan;54(1):72-77. doi: 10.1080/23744235.2021.1977382. Epub 2021 Oct 7.
Information about the contagiousness of new SARS-CoV-2 variants, including the alpha lineage, and how they spread in various locations is essential. Country-specific estimates are needed because local interventions influence transmissibility.
We analysed contact tracing data from Oslo municipality, reported from January through February 2021, when the alpha lineage became predominant in Norway and estimated the relative transmissibility of the alpha lineage with the use of Poisson regression.
Within households, we found an increase in the secondary attack rate by 60% (95% CI 20-114%) among cases infected with the alpha lineage compared to other variants; including all close contacts, the relative increase in the secondary attack rate was 24% (95% CI -6%-43%). There was a significantly higher risk of infecting household members in index cases aged 40-59 years who were infected with the alpha lineage; we found no association between transmission and household size. Overall, including all close contacts, we found that the reproduction number among cases with the alpha lineage was increased by 24% (95% CI 0%-52%), corresponding to an absolute increase of 0.19, compared to the group of index cases infected with other variants.
Our study suggests that households are the primary locations for rapid transmission of the new lineage alpha.
有关新 SARS-CoV-2 变体（包括阿尔法谱系）的传染性及其在不同地点传播方式的信息至关重要。由于当地干预措施会影响传染性，因此需要针对特定国家/地区进行估计。
我们分析了奥斯陆市 2021 年 1 月至 2 月期间报告的接触者追踪数据，当时阿尔法谱系在挪威占据主导地位，并使用泊松回归估计了阿尔法谱系的相对传染性。
在家庭中，与感染其他变体的病例相比，感染阿尔法谱系的病例的二次攻击率增加了 60%（95%CI 20-114%）；包括所有密切接触者，二次攻击率的相对增加为 24%（95%CI -6%-43%）。在感染阿尔法谱系的 40-59 岁的索引病例中，感染家庭成员的风险明显更高；我们未发现传播与家庭规模之间存在关联。总体而言，包括所有密切接触者，我们发现感染阿尔法谱系的病例的繁殖数增加了 24%（95%CI 0%-52%），与感染其他变体的索引病例组相比，绝对增加了 0.19。
我们的研究表明，家庭是新的阿尔法谱系快速传播的主要场所。
