The Coronavirus’ airborne spread: dust as a potential carrier?

The airborne transmission of the novel coronavirus had been thought to only be possible through close human contact and the inhalation of infectious droplets. But new research shows the coronavirus airborne spread can be extended and facilitated by fine dust particles in the air, as new research argues.

Research from Italy: particulate matter, Covid-19 and its anomalous spread.

The Coronavirus’ airborne spread was rapid across China and Europe, but particularly so in Northern Italy. © Edward Haas.

The Coronavirus crisis which has hit Europe in recent months has had its epicentre in Northern Italy, the most industrialised area of modern Italy, where cases far outstripped the rest of the country. It spread with a frightening rapidity and deadly effect not felt in other parts of Italy. Since the 12th of April still more than 30% of those currently suffering from Covid-19 hailed from the northern region of Lombardy, closely followed by the other northern regions of Emilia Romagna, Piedmont and Veneto. These regions have accounted for 80% of Italy’s Covid-19 related deaths, and 65% of its intensive care unit admissions. (Setti et al., 2020, April).

From its onset on scientists based in the universities and scientific facilities of Northern Italy led by Leonardo Setti have been investigating into its possible underlying cause: dust pollution. We report on their findings here.

Fine dust and the airborne transmission of viral diseases

To the uninitiated it might seem strange to even ponder upon a link between an airborne disease’s rate of infection and the rate of airborne particulate matter. But the Italian scientists were working upon scientific precedent: numerous papers in recent years have tied air pollution, and particularly particulate matter pollution, to the airborne spread of infectious diseases. A study in China linked high PM rates with measles outbreaks (Chen et al, 2017); historical research revealed the coinciding of the USA’s worst measles outbreak with the Dust Bowl of the 1930s (Alexander et al, 2018; Brown et al, 1935) , and another study pointed to dust’s likely role as a transporter of the Avian Flu in the 2015 outbreaks in Iowa (Zhao et al, 2019).

This precedent gave immediate cause to investigate the possible link between the particulate matter pollution of Northern Italy and its anomalously rapid spread of SARS-CoV-2. A glance at the compared timescales and results gave an unhappy confirmation of a definite correlation, if not a conclusive causal link.

The Coronavirus’ airborne spread in Northern Italy

First observed was the anomalously quick spread. The three northern regions worst hit by the virus, Lombardy, Emilia Romagna and Veneto, had far higher rates of infection than southern regions such as Puglia and Campagna, when comparing the numbers of confirmed cases from a base point of around 50 cases. Within 11 days, Lombardy had over 1500 confirmed cases, where Campagna had only 400. This trend held generally between the industrialised North and the less developed South.

They then looked into the local air pollution rates. It turned out that this anomalous spike in the infection rate in Northern Italy coincided with a spike in the local PM rates. The Southern regions experienced no such spike. This led naturally to the troubling yet plausible hypothesis that the spike in local PM rates was not an isolated, unconnected incident, but was rather the very cause for the spike in the rate of SARS-CoV-2 infections and consequent contracting of the Coronavirus disease.

They hypothesised that the dust had acted as a carrier for the virus, and had intensified the width and speed of its spread, just as those previous studies had established links between the particulate matter and other airborne infections. The existence of a similar connection between particulate matter and the SARS-CoV-2 virus would explain just why Northern Italy was hit so hard, so quickly, while Southern Italy was spared, and just why the two spikes of infections and particulate matter coincided so exactly.

This underlying causal link is yet to be conclusively proven, of course. The paper was published without peer-review, the process undertaken by the scientific community to assign scientific legitimacy to any research, due to the need for any kind of information which could be helpful in stemming the virus’ spread. Yet it seems clear that, in some manner at least, the coronavirus’ airborne spread and its concomitant rate of infection was connected to the local dust pollution.

Further study and further evidence

bergamo viewed at a distance from vantage point
Bergamo was one of the epicentres of the Covid-19 outbreak in Italy.

In recent days, the same group of scientists have made public a further study dedicated to trying to establish at least a provisional link. Its results confirmed it to within a reasonable level of certainty. They took air samples from an industrial site in Bergamo, a town which has become symbolic of the regions’ plight, and analysed them for the presence of RNA material highly specific to SARS-CoV-2.

They ran two separate analyses of the samples, so as to avoid any testing errors. In one test, they tested first only for the “E” gene, one of the three markers of SARS-CoV-2. In 15 of 16 samples it was found. These “E”-positive samples were further tested for the “RtDR gene”, another marker highly specific to the virus. In 5 of these tests, this marker was also found. In the second test of 34 different samples, 7 came out positive for one of the three SARS-CoV-2 markers.

The positive results across tests and of the varying different markers rule out with reasonable certainty mere coincidence or false positives. The scientists are tentative about the conclusions one can take from their findings, and they stress that more testing with larger samples sizes are necessary for conclusive proof of the connection.

Perhaps the dust particles act as a physical carrier for the virus, so that it can travel larger distances and transmit from human host to human host without close contact. Or perhaps it only provides a current of material in the air that the virus can travel in, due to its lower density than the dust particles. But, again, it is clear that the coronavirus’ airborne spread and its resulting rate of infection is connected to the rate of particulate matter pollution.

Conclusion: more dust, more Coronavirus cases.

The message to take from these two studies is clear, if the physical link not yet conclusively established. To restrict the amount of harm SARS-CoV-2 inflicts on our communities, we need to not only wash our hands thoroughly, and maintain appropriate distance, but we also need to ensure that dust pollution rates remain within safe levels, and reliably so. It is up to governments, regulatory bodies and private interests to ensure that this takes place. If we want to have an alternative to the simple cessation of industrial activities, effective dust suppression is required. Just like LAMI® provides.

Sources

Alexander, R et al, 2018. The Dust Bowl in the US: An Analysis Based on Current Environmental and Clinical Studies. The American Journal of the Medical Sciences. 356(2), 90-96. [Viewed online]. Available from: https://doi.org/10.1016/j.amjms.2018.03.015

Brown, E.G et al, 1935. Dust Storms and Their Possible Effect on Health: With Special Reference to the Dust Storms in Kansas in 1935. Public Health Reports (1896-1970). 50(40), 1369-1383. [Viewed online]. Available from: www.jstor.org/stable/4581653

Chen, G et al, 2017. Is Short-Term Exposure to Ambient Fine Particles Associated With Measles Incidence in China? A Multi-City Study. Environmental Research. 156, 306-311. [Viewed online]. Available from: https://doi.org/10.1016/j.envres.2017.03.046

Setti, L et al., 2020. Evaluation of the potential relationship between Particulate Matter (PM) pollution and COVID-19 infection spread in Italy. Available from: http://www.simaonlus.it/wpsima/wp-content/uploads/2020/03/COVID_19_position-paper_ENG.pdf

Setti, L et al., 2020. “SARS-Cov-2 RNA Found on Particulate Matter of Bergamo in Northern Italy: First Preliminary Evidence”, https://doi.org/10.1101/2020.04.15.20065995

Zhao, Y et al, 2019. Airborne transmission may have played a role in the spread of 2015 highly pathogenic avian influenza outbreaks in the United States. Scientific Reports. 9, 1-10. [Viewed online]. Available from: https://doi.org/10.1038/s41598-019-47788-z

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Recent studies have shown that the Coronavirus could attach itself to fine dust and travel over far distances. This could be a reason for the extreme spread in Italy.