The discovery, in a closed room, suggests that airborne transmission of the COVID-19 virus has a role in the pandemic.
The tricks that the new coronavirus has used to jump from a single infected at the end of November in China to the more than 20 million cases currently registered on the planet remains an enigma. The World Health Organization (WHO) insists that the virus is transmitted mainly by respiratory droplets, exhaled when coughing or speaking, during close and prolonged contact between two people. Despite pressure from a sector of the scientific community, the WHO is reluctant to recognise the so-called airborne transmission, defined as the spread of the virus suspended in the air for longer and at a greater distance, as occurs with measles or tuberculosis. Pakistani physician Faheem Younus summed it up in May with a masterful phrase: “If measles flies like an eagle, the coronavirus flies like a chicken.” A new study, however, suggests that the hen may flutter more than some thought.
The coronavirus has been found in the air almost five meters from a symptomatic patient in a room at a University of Florida hospital in Gainesville (USA), according to a preliminary study posted on August 4th. The great novelty of the work, unlike previous ones that had already found genetic material of the virus in the air, is that the authors have shown that the coronavirus is still “viable” floating almost five meters from a COVID-19 patient: the virus captured on the fly and taken to the laboratory, it is capable of infecting cells and multiplying in them. It is infective.
Furthermore, viruses caught in the air are genetically identical to those extracted from the throat of the symptomatic patient. According to Spanish engineer José Luis Jiménez, an aerosol expert at the University of Colorado (USA), the new study has found “the crime weapon”, proof that there may be an airborne transmission of the coronavirus in enclosed spaces.
“The implications for public health are numerous” say the authors, led by virologist John Lednicky of the University of Florida. Respiratory droplets, the main culprits in the transmission of COVID-19, according to the WHO, have a diameter of more than five-thousandths of a millimetre and soon fall to the ground by their own weight, although when evaporating they could produce aerosols, smaller in size, that hold more time in the air. “To avoid aerosol-based transmission, taking measures such as the physical distance of 1.8 meters would not be useful in an indoor space and would provide a false sense of security, causing exposure to the virus and outbreaks,” the authors stress.
Its preliminary study, pending acceptance in the journal of the International Society for Infectious Diseases, has not yet been comprehensively reviewed by independent researchers.
The WHO already warns of the possible airborne transmission of the coronavirus in hospitals, but only after medical procedures that generate aerosols, such as tracheal intubation of a patient. At the Florida hospital, the patients had not undergone any of these techniques: they were simply two people with COVID -19 talking or coughing in a windowless, but ventilated room. The air was changed six times an hour, with particle filters. In addition to the symptomatic patient, admitted the day before, there was another patient in the room about to be discharged.
The air we breathe is infested with viruses of all kinds —human, animal, plant, bacteriophage, but most of them are not infective due to factors such as ultraviolet light or desiccation, so they do not cause disease. The great challenge of the new study was to capture coronaviruses in the air without damaging them, to be able to demonstrate in the laboratory that they were still infectious. The Spanish researcher Arantza Eiguren has participated in the design of the ingenious device that for the first time has been able to carry out this task. The instrument, a box half a meter high, sucks the air out of the room and guides it through a hot section, where the water condenses and adheres to the suspended particles, which thus gain size and are easier to capture. “It is very similar to what your lungs do,” explains Eiguren, an aerosol expert at Berkeley-based Aerosol Dynamics (USA).
The WHO does not recognise the airborne transmission of the coronavirus, although it does not rule it out in closed, crowded and poorly ventilated spaces.
The device, as the researcher explains, detected up to 74 viral particles per litre of air, a “small” amount, perhaps because the room was well ventilated. The scientific community does not know the amount of coronavirus necessary to infect a person. “But if you are without a mask breathing that air for a while, in the end,, the exposure to the virus can be high,” warns Eiguren, who previously researched for a decade at the University of California in Los Angeles.
The latest specific WHO report, published on July 9, was sceptical of the airborne transmission hypothesis. “To date, SARS-CoV-2 has not been shown to be transmitted by that type of aerosol dissemination pathway. Given the possible repercussions that the confirmation of this transmission route would have, it is necessary to carry out much more research in this regard” the document stated. The WHO, however, recognized that “it cannot be ruled out that transmission by short-range aerosols has occurred, especially in specific closed environments, for example, places where there are infected people, there is overcrowding and insufficient ventilation is available for an extended period ”. The organisation cites suspicious outbreaks in restaurants and crowded and stuffy gyms.
A group of 36 international researchers has urged WHO to minimise possible airborne transmission in enclosed spaces through clear guidelines to improve ventilation. “It is very dangerous for us to rely on a single study that can still be rejected during review by other scientists”. The geologist recalls that previous investigations have already found genetic material of the virus floating in the air of some hospital rooms, for example, in Wuhan, the Chinese city where the pandemic began. The evidence accumulates. “I am not criticising the WHO. We only put up-to-date scientific evidence on the table. In our group of 36, we are mainly experts in air quality and atmospheric physics. We have an incomplete vision and we recognise that only WHO has the complete vision”, says a researcher.