Thursday, November 26

How can contagion be avoided on public transport?

Maintaining caution and being rigorous in social distancing, the use of masks and hygiene is the best way to reduce the risk of contagion of covid-19 in public transport compared to the threat of aerosol transmission.

These are the advice of the public health experts consulted by EFE, in the absence of greater knowledge about the transmission of the disease.

For it advocate avoiding peak hours of public transportation, stagger the start of working hours or resort directly to teleworking, increase the frequencies, as well as use approved masks correctly and maintain good hand hygiene.

Closed spaces

Scientific research warns about the risk of contagion through particles emitted by infected people that differ by their size in droplets, from 0.3 millimeters to 1 millimeter thick, and aerosols, smaller than the diameter of a human hair.

The droplets are projected up to a meter away, while aerosols are suspended in the atmosphere, where they can remain for hours, which makes them especially dangerous in closed spaces without ventilation.

One of the latest studies that addresses the importance of aerosols in the spread of the disease is the “Scientific Report on SARS-CoV-2 transmission routes”, prepared for the Ministry of Science by a group of experts.

The report is signed, among other authors, by the virologist from the Higher Center for Scientific Research (CSIC) Margarita del Val, the epidemiologist from Harvard University Miguel Hernán and the researcher from the Institute for Environmental Diagnosis and Water Studies (IDAEA), dependent on the CSIC, Xavier Querol.

The writing group of this study underscores existing “significant evidence” on aerosol transmission, which they point to as a possible “dominant form of transmission” versus the probably “overestimated” pathway for droplets.

Added to these two forms of contagion is the threat posed by contact with contaminated surfaces.

Reduce risk

The discrepancies between the researchers confirm that information on how transmission occurs is missing of the covid-19.

It is also difficult to determine the real risk of contracting the disease in public transport because it is not known where the patients who use it have been infected, since they move in different environments.

Faced with so much uncertainty, what should prevail is the precautionary principle“One of the authors of the report for the Ministry of Science, Xavier Querol, explains in statements to EFE.

That means “measures must be taken to reduce the risk to the maximum “, adds the CSIC Research professor.

The “precautionary principle” is also invoked by the spokesperson for the Spanish Society of Public Health and Health Administration (SESPAS), Ildefonso Hernández, to ensure the adoption of basic measures “with the greatest possible detail.”

How do you keep your distance?

The first of these basic measures is the maintaining a distance of one and a half meters from other people that avoids being reached by droplets with viral load.

To achieve this distance, these experts ask that public administrations increase the frequencies.

Users can in turn avoid peak passenger traffic hours.

Querol proposes stagger working hours, something that depends on the agreement of companies and employees, or resorting directly to teleworking.

It also raises the need to install capacity sensors in buses and wagons and prevent entry when the limit is exceeded that makes it impossible to maintain a meter and a half distance between people.

He adds that buses and wagons have correct ventilation systems that reduce the risk of contagion.

What masks should be used?

The CSIC Research professor highlights the importance of using masks of “material that is well filtering” and correctly adjusted, without letting air pass over the edges.

Remember that there are cloth masks that do not comply with the regulations and that hygienic masks are convenient – as long as they are within the parameters of the Spanish Association for Standardization (UNE) -, surgical ones and FPP2 and FPP3, without exhalation valves.

Remember that hygienic and surgical protect those close to those who wear themwhile FPP2s and FPP3s without valves protect both those who use them and those around them.

This is not true when they have exhalation valves, which let the air emitted by the wearer escape, which means that these masks avoid risks for their wearer but are dangerous for others.

To comply with the principle of maximum care in the adoption of these measures, Ildefonso Hernández recommends the use of FPP2 masks if the trip is very long, on a six-hour train ride, for example.

This expert, who is also a professor of Public Health at the Miguel Hernández University of Elche (Alicante) and was director general of Health of the Ministry of Health from 2008 to 2011, recalls the need for the Government to lower the price of masks to facilitate its renewal and asks that it provide this element of protection to people in vulnerable situations.

On the other hand, in an interview on the Catalan radio station RAC1, the researcher specialized in aerosols from the IDAEA-CSIC María Cruz Minguillón advised on November 1 that, in addition to wearing the mask, the passengers were silent in the subway.

Minguillón also demanded that the authorities signal it.

As a result of this request, the Catalan Government has decided to request silence from the passengers of the Ferrocarriles de la Generalitat trains, something that Transportes Metropolitanos de Barcelona also does by metro and buses.

Caution on surfaces

Despite recent studies that relativize the importance of contagion by contact with surfaces contaminated by COVID-19 patients, Querol and Hernández once again ask for caution and take extreme care until this information is duly verified.

For this, his advice is to apply another general basic measure: maintain correct hand hygiene and avoid touching your face after having come into contact with any element inside a bus or wagon.

Querol recommends that the administrations that manage public transport make hydroalcoholic gel dispensers available to travelers at stops and inside vehicles.

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