SARS-CoV-2 Coronavirus Is Evolving To Become Better At Airborne Transmissions

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University of Maryland Study Shows That SARS-CoV-2 Coronavirus Is Evolving To Become Even Better At Airborne Transmissions.

o date, SARS-CoV-2 epidemiology implicates airborne transmission but aerosol infectiousness and impacts of masks and variants on aerosol shedding are not well understood.

The study team recruited COVID-19 patients to give blood, saliva, mid-turbinate and fomite (phone) swabs, and 30-minute breath samples while vocalizing into a Gesundheit-II(A machine that measures viruses in exhaled breath), with and without masks at up to two visits two days apart; then quantified and sequenced viral RNA, cultured virus, and assayed sera for anti-spike and anti-receptor binding domain antibodies.

In all a total of 49 seronegative cases were also enrolled (mean days post onset 3.8 ±2.1), May 2020 through April 2021.

They detected 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.

Importantly 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 study findings confirm that SARS-CoV-2 is evolving toward more efficient aerosol generation and loose-fitting masks provide significant but only modest source control.

Hence, until vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.
reference link: Clinical Infectious Diseases. https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab797/6370149

Study findings show that individuals infected with the SARS-CoV-2 virus that causes COVID-19 exhale infectious virus in their breath and those infected with the Alpha variant (the dominant strain circulating at the time this study was conducted) put 43 to 100 times more virus into the air than people infected with the original strains of the virus.

The team also found that loose-fitting cloth and surgical masks reduced the amount of virus that gets into the air around infected people by  only about half.

Corresponding author, Dr Donald K  Milton, professor of environmental health at the University of Maryland School of Public Health (UMD SPH) told : “Our latest study provides further evidence of the importance of airborne transmission. We know that the Delta variant circulating now is even mor e contagious than the Alpha variant.

Our study findings indicates that the variants just keep getting better at traveling through the air, so we must provide better ventilation and wear tight-fitting masks, in addition to vaccination, to help stop spread of the virus.”

Importantly it was found that the amount of virus in the air coming from Alpha variant infections was much more ie 18-times more than could be explained by the increased amounts of virus in nasal swabs and saliva.

Lead authors, doctoral student Jianyu Lai, explained, “We already knew that virus in saliva and nasal swabs were increased in Alpha variant infections. Virus from the nose and mouth might be transmitted by sprays of large droplets up close to an infected person. But, our study shows that the virus in exhaled aerosols is increasing even more.”

Significantly these major increases in airborne virus from Alpha infections occurred before the Delta variant arrived and indicate that the virus is evolving to be better at traveling through the air.

In order  to test whether face masks work in blocking the virus from being transmitted among people, this study measured how much SARS-CoV-2 is breathed into the air and tested how much less virus people sick with COVID-19 exhaled into the air after putting on a cloth or surgical mask.

The SARS-CoV-2-Airborne study finding showed that face coverings significantly reduced virus-laden particles in the air around the person with COVID-19, cutting the amount by about 50%.

However the loose-fitting cloth and surgical masks didn’t stop infectious virus from getting into the air.

Co-author, Dr Jennifer German, a professor at the Public Health Aerobiology and Biomarker Laboratory, Institute for Applied Environmental Health, University of Maryland School of Public Health said, “The take-home messages from this study findings are that the SARS-CoV-2 coronavirus that can be in your exhaled breath, is getting better at being in your exhaled breath, and using a mask reduces the chance of you breathing it on others.

This means that a layered approach to control measures (including improved ventilation, increased filtration, UV air sanitation, and tight-fitting masks, in addition to vaccination) is critical to protect people in public-facing jobs and indoor spaces.”


In urban areas, global anthropogenic air pollution is pervasive (Groulx et al., 2018). The rapid urbanization, industrial activities, substantial energy consumption, and economic growth are indicated by a significant increase in traffic and the worsening air quality in the developing countries (Lu et al., 2018; Yan et al., 2019).

High ambient particulate matter (PM) exposure can be responsible for unintended human health effects (Lu et al., 2018). Repeated hazy days can be caused by fine particulate matter (PM2.5) in China, and many other Asian megacities have caused substantial environmental and public health crises (Xie et al., 2018).

Subsequently, World Air Quality Report 2019 stated the accretion of airborne PM and its atmospheric and environmental disturbances around the Asian and South Asian countries (IQAir 2020). Yet in 2020, lockdown actions to reduce COVID-19 pandemic across many Asian megacities have resulted in a substantial shift in air pollution.

When a consortium of airborne microorganisms of numerous sizes and types are present in the air in association with PMs, it is called airborne particles or bioaerosols (Caruana, 2011). It combines solids and semi-solids material in association with biotic and abiotic pieces with sizes ranging from 0.001 nm to 100 μm (Humbal et al., 2018).

Bioaerosols may comprise 15–25% of PM by mass combined with living or dead bacteria, fungi, viruses, secondary metabolites, pollens, and dust (Ghosh et al., 2015; Samake et al., 2017). The study of airborne bioaerosols has gained significant interest in recent years (Fatahinia et al., 2018).

Bioaerosols can result in infectious diseases, respiratory and chronic health issues (Valdez-Castillo and Arriaga 2021). Considering the recent COVID-19 pandemic, bioaerosols might have a significant role to play in the transmission of coronavirus (Noorimotlagh et al., 2020).

A growing quantity of data implying that the airborne microbial portion of the particulate matter is responsible for critically escalating adverse effects on public health (Gandolfi et al., 2013).

Bacteria contribute significantly to the occurrence and composition of airborne aerosols formed by seasonal changes induced by the atmospheric and local terrestrial environment (Bowers et al., 2012). Furthermore, concentrations of cultured bacteria and fungi showed a strong connection to the AQI.

When AQI <200, the concentration of airborne fungi gradually increased while AQI>200 increased airborne bacteria (Yan et al., 2019). Chemical composition, along with microbiological compositions, is significant in identifying the relationships between PM and AQI and, thus, the microorganism residing in them (Gandolfi et al., 2013).

However, the question is why bioaerosols increase with air pollution remaining unclear. One hypothesis may be that high or extreme pollution levels primarily affect the diversity and composition of bioaerosols (Fan et al., 2019). The viability of the microbes in the bioaerosols depends on the surrounding environment, climate, and atmospheric chemistry, in conjunction with microbial concentrations (Gong et al., 2020).

Therefore, knowing the microbiological structure and composition of PM is necessary to identify the mode of disease transmission and the possible human health impact (Wang et al., 2019).

South Asia and many other Asian megacities are currently undergoing rapid development in urban and industrial sectors and eventually deteriorating the air quality. Thus, this review aims to identify bioaerosols in relationship with PM reported from Asian megacities and their impact on human health.

reference link : https://www.frontiersin.org/articles/10.3389/fenvs.2021.698215/full

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