Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains
We studied the secondary attack rate (SAR), risk factors, and precautionary practices of household transmission in a prospective, longitudinal study. We further compared transmission between the Alpha (B.1.1.7) variant and non-Variant of Concern (non-VOC) viruses. From May 2020 throughout April 2021...
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2021
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oai:doaj.org-article:56d683ea6a524fc887986890707876562021-11-25T18:25:29ZHousehold Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains10.3390/microorganisms91123712076-2607https://doaj.org/article/56d683ea6a524fc887986890707876562021-11-01T00:00:00Zhttps://www.mdpi.com/2076-2607/9/11/2371https://doaj.org/toc/2076-2607We studied the secondary attack rate (SAR), risk factors, and precautionary practices of household transmission in a prospective, longitudinal study. We further compared transmission between the Alpha (B.1.1.7) variant and non-Variant of Concern (non-VOC) viruses. From May 2020 throughout April 2021, we recruited 70 confirmed COVID-19 cases with 146 household contacts. Participants donated biological samples eight times over 6 weeks and answered questionnaires. SARS-CoV-2 infection was detected by real-time RT-PCR. Whole genome sequencing and droplet digital PCR were used to establish virus variant and viral load. SARS-CoV-2 transmission occurred in 60% of the households, and the overall SAR for household contacts was 50%. The SAR was significantly higher for the Alpha variant (78%) compared with non-VOC viruses (43%) and was associated with a higher viral load. SAR was higher in household contacts aged ≥40 years (69%) than in younger contacts (40–47%), and for contacts of primary cases with loss of taste/smell. Children had lower viral loads and were more often asymptomatic than adults. Sleeping separately from the primary case reduced the risk of transmission. In conclusion, we found substantial household transmission, particularly for the Alpha variant. Precautionary practices seem to reduce SAR, but preventing household transmission may become difficult with more contagious variants, depending on vaccine use and effectiveness.Cathinka Halle JulinAnna Hayman RobertsonOlav HungnesGro TunheimTerese BekkevoldIda LaakeIdunn Forland AuneMarit Fodnes KillengreenTorunn Ramsem StrandRikard RykkvinDagny Haug DorenbergKathrine Stene-JohansenEinar Sverre BergJohanna Eva BodinFredrik OftungAnneke SteensLisbeth Meyer NæssMDPI AGarticlehousehold transmissionSARS-CoV-2COVID-19Alpha variantB.1.1.7secondary attack rateBiology (General)QH301-705.5ENMicroorganisms, Vol 9, Iss 2371, p 2371 (2021) |
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household transmission SARS-CoV-2 COVID-19 Alpha variant B.1.1.7 secondary attack rate Biology (General) QH301-705.5 |
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household transmission SARS-CoV-2 COVID-19 Alpha variant B.1.1.7 secondary attack rate Biology (General) QH301-705.5 Cathinka Halle Julin Anna Hayman Robertson Olav Hungnes Gro Tunheim Terese Bekkevold Ida Laake Idunn Forland Aune Marit Fodnes Killengreen Torunn Ramsem Strand Rikard Rykkvin Dagny Haug Dorenberg Kathrine Stene-Johansen Einar Sverre Berg Johanna Eva Bodin Fredrik Oftung Anneke Steens Lisbeth Meyer Næss Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| description |
We studied the secondary attack rate (SAR), risk factors, and precautionary practices of household transmission in a prospective, longitudinal study. We further compared transmission between the Alpha (B.1.1.7) variant and non-Variant of Concern (non-VOC) viruses. From May 2020 throughout April 2021, we recruited 70 confirmed COVID-19 cases with 146 household contacts. Participants donated biological samples eight times over 6 weeks and answered questionnaires. SARS-CoV-2 infection was detected by real-time RT-PCR. Whole genome sequencing and droplet digital PCR were used to establish virus variant and viral load. SARS-CoV-2 transmission occurred in 60% of the households, and the overall SAR for household contacts was 50%. The SAR was significantly higher for the Alpha variant (78%) compared with non-VOC viruses (43%) and was associated with a higher viral load. SAR was higher in household contacts aged ≥40 years (69%) than in younger contacts (40–47%), and for contacts of primary cases with loss of taste/smell. Children had lower viral loads and were more often asymptomatic than adults. Sleeping separately from the primary case reduced the risk of transmission. In conclusion, we found substantial household transmission, particularly for the Alpha variant. Precautionary practices seem to reduce SAR, but preventing household transmission may become difficult with more contagious variants, depending on vaccine use and effectiveness. |
| format |
article |
| author |
Cathinka Halle Julin Anna Hayman Robertson Olav Hungnes Gro Tunheim Terese Bekkevold Ida Laake Idunn Forland Aune Marit Fodnes Killengreen Torunn Ramsem Strand Rikard Rykkvin Dagny Haug Dorenberg Kathrine Stene-Johansen Einar Sverre Berg Johanna Eva Bodin Fredrik Oftung Anneke Steens Lisbeth Meyer Næss |
| author_facet |
Cathinka Halle Julin Anna Hayman Robertson Olav Hungnes Gro Tunheim Terese Bekkevold Ida Laake Idunn Forland Aune Marit Fodnes Killengreen Torunn Ramsem Strand Rikard Rykkvin Dagny Haug Dorenberg Kathrine Stene-Johansen Einar Sverre Berg Johanna Eva Bodin Fredrik Oftung Anneke Steens Lisbeth Meyer Næss |
| author_sort |
Cathinka Halle Julin |
| title |
Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| title_short |
Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| title_full |
Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| title_fullStr |
Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| title_full_unstemmed |
Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains |
| title_sort |
household transmission of sars-cov-2: a prospective longitudinal study showing higher viral load and increased transmissibility of the alpha variant compared to previous strains |
| publisher |
MDPI AG |
| publishDate |
2021 |
| url |
https://doaj.org/article/56d683ea6a524fc88798689070787656 |
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