Studies suggest COVID-19 is evolving to spread more efficiently through air

By Dr Deepu Changappa Cheriamane

The newer variants of the coronavirus like Alpha and Delta are highly contagious, infecting far more people than the original virus. The virus is evolving to spread more efficiently through air. The studies have signalled the need for better masks in some situations, and indicate that the virus is changing in ways that make it more formidable. We still have best tools at our disposal, which still work well to halt the spread.

Even a loosefitting cloth and surgical masks block about half of the fine aerosols containing virus, according to the study of people infected with variants, published this month in the journal Clinical Infectious Diseases.

Here is a brief summary of the study.

The authors recruited 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 two visits two days apart. Later the researchers quantified and sequenced viral RNA, cultured virus, and assayed sera for anti-spike and anti-receptor binding domain antibodies.

The researchers enrolled 49 seronegative cases (mean days post onset 3.8 ±2.1), May 2020 through April 2021. They could detect SARS-CoV-2 RNA in 45% of fine (≤5 µm), 31% of coarse (>5 µm) aerosols, and 65% of fomite samples overall and in all samples from four 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. 

They also found that 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.

The authors concluded that the SARS-CoV-2 is evolving toward more efficient aerosol generation and loose-fitting masks provide significant but only modest source control. They ended quoting that "until

vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.

Click here to read the published study