Covid19 Part XVI- 21,983 in ROI (1,339 deaths) 3,881 in NI (404 deaths)(05/05)Read OP

podgeandrodge wrote: »

I'm not disagreeing with you Rob, only saying the jury is out. Here are a couple of articles that give both sides of the potential for aerosols. I don't claim to know which is right, only that nothing appears proven yet.

I've bolded a few bits that suggest to me that it is not yet proven. Bolding those bits does not mean I am discounting the rest of the text in the articles that suggests it could be.

https://today.rtl.lu/news/science-and-environment/a/1498185.html

Hendrik Streeck, professor for virology and the director of the Institute of virology and HIV Research at the University Bonn explained the methodology of his new study in Heinsberg, the “epicentre” of Germany’s COVID-19 outbreak, and talked about potential plans for a country to move forward gradually in getting back to a “normal” life.

During recent weeks, his team completed substantial research conducted through surveys and investigations in homes across the Heinsberg region - where more than 1,400 confirmed cases had been reported. Heinsberg has an approximate population of 250,000 inhabitants and has confirmed 46 coronavirus-related deaths.

These research findings have already provided some indication on how the virus works, as Streeck clarified:

“There is no significant risk of catching the disease when you go shopping. Severe outbreaks of the infection were always a result of people being closer together over a longer period of time, for example the après- ski parties in Ischgl, Austria.” He could also not find any evidence of ‘living’ viruses on surfaces. “When we took samples from door handles, phones or toilets it has not been possible to cultivate the virus in the laboratory on the basis of these swabs….”

“To actually 'get' the virus it would be necessary that someone coughs into their hand, immediately touches a door knob and then straight after that another person grasps the handle and goes on to touches their face.” Streeck therefore believes that there is little chance of transmission through contact with so-called contaminated surfaces.

The fact that COVID 19 is a droplet infection and cannot be transmitted through the air had previously also been confirmed by virologist Christian Drosten of Berlin's Charité. He had pointed out in an interview that coronavirus is extremely sensitive to drying out, so the only way of contracting it is if you were to “inhale the droplets.”

However, there are different findings on how the coronavirus spreads. Experts from the US Institute of Health CDC and NIH had come to the conclusion that the virus can survive 24 hours on paper, three hours in aerosols and up to three days on plastics and stainless steel. As the Robert Koch Institute states on their website, however, scientific studies like this are realised under experimental conditions, which is why they are not very representative for the risk of transmission in daily life.

Heinsberg will now be the centre for conducting another study, which goes deeper, aiming to further evaluate how the virus spreads and how it can be contained. The study will follow a representative sample of 1,000 people.
“It is important to obtain this data in order to make sure that decisions are taken based on facts rather than assumptions. The data should serve as a basis of information for the government so they can then think about their further course of action,” he continues.




http://blog.pnas.org/2020/04/fluid-dynamics-work-hints-at-whether-spoken-word-can-spread-covid-19/

Fluid dynamics work hints at whether spoken word can spread COVID-19

A sneeze can project a droplet-containing gas cloud seven or eight meters, possibly spreading disease. But the spoken word is also far from innocuous.

As of April 3, the Centers for Disease Control and Prevention (CDC) is advising that everyone—sick or healthy—wear masks to prevent the spread of COVID-19. Recent research on how fluids travel from our respiratory tracts when we sneeze, speak, or breathe shows why the practice could be so important—even if it can’t yet explain exactly how coronavirus spreads so quickly or definitively determine whether masks or face coverings for all will significantly reduce disease spread.

When a person coughs or sneezes, large fluid droplets that may contain pathogens go flying. Respiratory infections can spread when another person comes into direct contact with these droplets or touches a surface contaminated by them.

In addition to these visible droplets, the largest of which are formed by saliva, we also expel much smaller droplets that can originate in the mucous coating of the lungs and vocal chords. These smaller droplets, often called aerosol particles, are invisible to the naked eye, and behave somewhat like dust particles suspended in a sunlit room, says William Ristenpart, a chemical engineer at the University of California, Davis. “These aerosol particles that are about one micrometer can stay in the air for a very long time—hours.”

Lydia Bourouiba, director of the Fluid Dynamics of Disease Transmission Laboratory at the Massachusetts Institute of Technology, uses optical methods like backlighting combined with high-speed videography—1,000 frames per second or more—to help quantify the physics of pathogen transport with exhalations like a cough or sneeze. Her team’s findings, reported in the Journal of Fluid Mechanics in 2014 and Experiments in Fluids in 2016, show that most respiratory droplets do not travel independently on their own trajectories.
Instead, droplets in a continuum of sizes are trapped and carried forward within a moist, warm, turbulent cloud of gas. “This cloud makes the droplets concentrated, and carried forward further than they would be able to reach otherwise,” Bourouiba says, adding that this “potentially changes the physics of evaporation.”

The simple act of speaking also propels droplets into the air—though typically too small to be visible. Ristenpart and his team used an aerodynamic particle sizer to record the number and size distribution of droplets emitted as people spoke at a range of different volumes. Their research, described in Scientific Reports in 2019, revealed that as people raise their voices, they emit more droplets, but the size distribution of the droplets remains the same. This finding was true regardless of the language spoken.

Even breathing could release potentially infectious aerosols, says Donald Milton, an infectious disease aerobiologist at the University of Maryland School of Public Health. Milton and his team collected droplets from volunteers with flu symptoms by asking them to spend 30 minutes with their faces positioned in front of the large opening of a cone as it drew in air. The device captured the large droplets produced by sneezing and coughing as well as the aerosolized droplets produced by sneezing, coughing, breathing and talking on different surfaces. His team recorded the number of times each participant coughed and sneezed. They also asked the participants to say the alphabet three times, so some of the droplets the team collected were likely released during speech. “People didn’t have to cough to shed virus,” Milton explains. The work, published in PNAS in 2018, shows that the flu virus exists even in the tiny aerosolized droplets resulting from breath or speech alone. It is not yet confirmed, however, whether exposure to these aerosolized droplets could lead to flu infection.

Researchers are still exploring whether fine aerosolized droplets could spread coronavirus. The data are not yet conclusive, says Yvonne Maldonado, infectious disease epidemiologist at the Stanford University School of Medicine. One question is whether this virus can survive in a 5-micrometer particle for a long period of time in a healthcare environment, she says. “Because that would mean that if you walked into a room, you would just have to breathe to become infected.”

Maldonado thinks that scenario is unlikely. “Fortunately for us, there aren’t very many known aerosol viruses,” she says. Measles and tuberculosis are among the few exceptions.

Still, some researchers believe that transmission via tiny droplets warrants a closer look. “We know that asymptomatic people are transmitting COVID-19 and they’re not coughing,” says Milton. He points to a preprint study, not yet peer reviewed, by researchers at the University of Nebraska Medical Center that suggests that coronavirus was present in air samples collected from the rooms of individuals infected with coronavirus, regardless of whether the patients showed symptoms like coughing and sneezing.

The White House Office of Science and Technology Policy recently asked the National Academies Standing Committee on Emerging Infectious Diseases and 21st Century Health Threats to consider whether the SARS-CoV-2 virus could be spread by conversation, in addition to sneeze/cough-induced droplets. The team determined that current evidence supports the possibility that COVID-19 could spread through aerosolized droplets released via patients’ exhalations. They noted, however, that the latest research, including the Nebraska study, does not yet confirm whether the coronavirus identified in air samples is actually viable and capable of infecting those who breathe it in.

Because speech can release droplets, and many contagious individuals do not know that they are infected, some public health experts are suggesting that we should all wear a mouth covering when we need to go out in public. “Eliminating speech droplets could be a significant part of reducing community spread,” says Anne Rimoin, a professor of epidemiology at the University California, Los Angeles, Fielding School of Public Health. Medical masks, she cautions, should be reserved for medical personnel. “What we’re talking about is that a simple cloth mask or face covering can stop droplets from spreading.”

A homemade cloth mask wouldn’t stop the small aerosolized droplets, says Rimoin. And public health experts often warn against wearing them because they can become contaminated if not handled properly, notes Maldonado.
Still, despite these limitations, homemade masks could still do a great deal of good, says Rimoin. “We are so used to working in a system where perfection is our goal, but we are in the greatest public health emergency of our lifetime and, as such, we have to get creative and do the best we can and not let the great be the enemy of the good.

The CDC has now called on all persons to wear cloth face coverings, though the fear remains that this guidance could prompt a run on medical masks that are already in short supply for the healthcare workers who need them most. The CDC guidance does specify that the recommended face coverings are “not surgical masks or N-95 respirators” which are “critical supplies that must continue to be reserved for healthcare workers and other medical first responders.” They offer tips on how to make face coverings from cotton fabric, t-shirts, or bandanas and coffee filters at home. “The key is that these are two separate issues: Facial coverings for the general public to keep their droplets to themselves, and an urgent and critical need for PPE for healthcare workers,” says Rimoin. “It’s not reasonable to expect our healthcare workers to be out there without the protection that they need.”

Another possible reason to wear a mask is that six feet between individuals may not provide wide enough berth to limit spread via even the larger droplets. In a recent article published in the Journal of the American Medical Association, MIT’s Bourouiba notes that under the right temperature and humidity conditions, a sneeze can release a gas cloud that carries droplets within it as far as seven to eight meters.

Many questions remain about the fluid dynamics of how coronavirus is transmitted. In a recently published editorial in Aerosol Science and Technology, Ristenpart and colleagues suggest that face-to-face conversation is a plausible hypothesis. But they note many unknowns, including whether aerosols produced by speech actually contain the virus and, if so, how temperature and humidity affect its viability. “Clearly [coronavirus] is highly transmittable. Clearly it is in the respiratory tract,” says Ristenpart. “We need more experimentation.”

Rob A. Bank wrote: »

Thank you.... Very impressive research but the bottom line is that the jury is still out until further research is done.

The droplet theory is based on TB research from the 1930s, William F. Wells's droplet nucleus hypothesis . He divided the droplets into large and small in a not very scientific way. That seems to be where the 2 meter rule came from too.

It was theorized that the small droplets (aerosols) would dry up quickly and thus become inactive. The recent discoveries of viable Sars viruses in air conditioning systems on ships, residential blocks and in hospitals would suggest that the aerosol route may be more important than was thought possible to date.

Surely the safety principle should dictate that masks, even homemade cloth ones, are useful for the public... until such time as research delivers a definite answer.