"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," the researchers concluded in their findings, published by Oxford University Press for the Infectious Diseases Society of America this week.

The research was conducted in May 2020 - April 2021 and SARS-CoV-2 RNA was detected in all samples from the alpha-variant cases.

"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," the researchers said.

The alpha variant was first detected in November 2020 from a sample taken in September in the United Kingdom. The alpha quickly became the most common strain in Europe and then the US but has since become less common as the delta variant has taken over.