{"doi":"10.1093/cid/ciab797","title":"Infectious Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Exhaled Aerosols and Efficacy of Masks During Early Mild Infection","abstract":"BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemiology implicates airborne transmission; aerosol infectiousness and impacts of masks and variants on aerosol shedding are not well understood. METHODS: We recruited coronavirus disease 2019 (COVID-19) cases to give blood, saliva, mid-turbinate and fomite (phone) swabs, and 30-minute breath samples while vocalizing into a Gesundheit-II, with and without masks at up to 2 visits 2 days apart. We quantified and sequenced viral RNA, cultured virus, and assayed serum samples for anti-spike and anti-receptor binding domain antibodies. RESULTS: We enrolled 49 seronegative cases (mean days post onset 3.8 ± 2.1), May 2020 through April 2021. We detected SARS-CoV-2 RNA in 36% of fine (≤5 µm), 26% of coarse (>5 µm) aerosols, and 52% of fomite samples overall and in all samples from 4 alpha variant cases. Masks reduced viral RNA by 48% (95% confidence interval [CI], 3 to 72%) in fine and by 77% (95% CI, 51 to 89%) in coarse aerosols; cloth and surgical masks were not significantly different. The alpha variant was associated with a 43-fold (95% CI, 6.6- to 280-fold) increase in fine aerosol viral RNA, compared with earlier viruses, that remained a significant 18-fold (95% CI, 3.4- to 92-fold) increase adjusting for viral RNA in saliva, swabs, and other potential confounders. Two fine aerosol samples, collected while participants wore masks, were culture-positive. CONCLUSIONS: SARS-CoV-2 is evolving toward more efficient aerosol generation and loose-fitting masks provide significant but only modest source control. Therefore, until vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.","journal":"Clinical Infectious Diseases","year":2021,"id":148738,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":120,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9544,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2021-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":632757,"name":"Jianyu Lai","orcid":"0000-0001-5705-0138","position":1,"is_corresponding":false},{"id":632758,"name":"P. Jacob Bueno de Mesquita","orcid":"0000-0001-5991-0138","position":2,"is_corresponding":false},{"id":550223,"name":"Filbert Hong","orcid":"0000-0003-2289-5119","position":3,"is_corresponding":false},{"id":633716,"name":"Somayeh Youssefi","orcid":null,"position":4,"is_corresponding":false},{"id":632759,"name":"Jennifer German","orcid":"0000-0003-3196-4083","position":5,"is_corresponding":false},{"id":424703,"name":"Sheldon Tai","orcid":"0000-0001-6834-2152","position":6,"is_corresponding":false},{"id":632760,"name":"Barbara Albert","orcid":"0000-0002-2696-521X","position":7,"is_corresponding":false},{"id":632761,"name":"Maria Schanz","orcid":"0000-0003-3292-4278","position":8,"is_corresponding":false},{"id":474931,"name":"Stuart Weston","orcid":"0000-0001-9840-2953","position":9,"is_corresponding":false},{"id":583487,"name":"Jun Hang","orcid":"0000-0002-6597-7045","position":10,"is_corresponding":false},{"id":497141,"name":"Christian Fung","orcid":"0000-0002-8709-5932","position":11,"is_corresponding":false},{"id":632762,"name":"Hye Kyung Chung","orcid":"0000-0003-4129-4124","position":12,"is_corresponding":false},{"id":311395,"name":"Kristen K. Coleman","orcid":"0000-0003-0024-3400","position":13,"is_corresponding":false},{"id":229070,"name":"Nicolae Sapoval","orcid":"0000-0002-0736-5075","position":14,"is_corresponding":false},{"id":29176,"name":"Todd J. Treangen","orcid":"0000-0002-3760-564X","position":15,"is_corresponding":false},{"id":290884,"name":"Irina Maljkovic Berry","orcid":"0000-0001-8555-5352","position":16,"is_corresponding":false},{"id":633717,"name":"Kristin Mullins","orcid":null,"position":17,"is_corresponding":false},{"id":218418,"name":"Matthew B. Frieman","orcid":"0000-0003-0107-0775","position":18,"is_corresponding":false},{"id":327030,"name":"Tianzhou Ma","orcid":"0000-0003-3605-0811","position":19,"is_corresponding":false},{"id":550224,"name":"Donald K. Milton","orcid":"0000-0002-0550-7834","position":20,"is_corresponding":false},{"id":550222,"name":"Oluwasanmi Adenaiye","orcid":"0000-0003-1888-5022","position":0,"is_corresponding":true}],"reference_count":31,"raw_metadata":null,"created_at":"2026-07-18T23:42:46.224799Z","pmid":"34519774","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}