Tag Archives: ‘Invisible’

Scientists try to ‘see’ invisible transmission of coronavirus through respiratory droplets

This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven’t subscribed yet, you can do that by clicking here.


The coronavirus that causes COVID-19 spreads through droplets that we spew as we breathe, talk, cough and sneeze — so tiny that they’re invisible to the naked eye. 

That’s why questions remain about the virus’s transmission and what precautions need to be taken to curb its spread as governments begin to lift restrictions. Will it help if everyone wears a mask? Is keeping everyone two metres apart far enough?

Some researchers aim to learn more about transmission by trying to make invisible sneezes, coughs and breaths more visible. Here’s a closer look at that research and what it might reveal.

How do scientists think COVID-19 is transmitted?

According to the World Health Organization, the disease spreads primarily through tiny droplets expelled when a person infected with SARS-CoV-2 sneezes, coughs, exhales or spits while talking. They can infect another person who:

  • Comes into contact with those droplets through their eyes, nose or mouth (droplet transmission).

  • Touches objects or surfaces on which droplets have landed and then touches their eyes, nose or mouth (contact transmission).

The WHO says it’s important to stay “more than one metre away” from a person who is sick. But the Public Health Agency of Canada recommends staying a distance of at least two metres or two arms’ lengths away, not just from people who are sick but from all people you don’t live with.

Why is 2 metres the recommended distance for preventing transmission?

Scientists in the 19th century showed respiratory droplets from a person’s nose and mouth can carry micro-organisms such as bacteria and viruses.

Then, in 1934, W.F. Wells at the Harvard School of Public Health showed that large droplets (bigger than 0.1 millimetre) tended to fall and settle on the ground within a distance of two metres, while smaller droplets evaporated and the virus particles left behind could remain suspended in the air for a long time.


Wells proposed that could explain how diseases are transmitted.

Since then, respiratory diseases have been divided into those transmitted via droplets (usually from close contact) and those that are airborne and can spread over longer distances, such as measles or tuberculosis. 

Such tiny particles are presumably pushed around by air currents, but can’t move easily due to air resistance. So their actual movements haven’t been well modelled or measured, said Lydia Bourouiba, professor and director of the Fluid Dynamics of Disease Transmission Laboratory at the Massachusetts Institute of Technology. 

“And that’s why the notion of airborne [transmission] is very murky,” said Bourouiba, who is Canadian.

Why don’t experts think the virus is airborne?

A pair of recent studies raised the notion of airborne transmission, but Mark Loeb, a professor at Hamilton’s McMaster University who specializes in infectious disease research, cautions against putting too much stock in them. 

Researchers found traces of RNA from SARS-CoV-2 in washrooms and some high-traffic areas in hospitals in Wuhan, China, and in Nebraska, and suggested it got into those areas through the air, though there was no evidence the particles were still infectious. 


Government guidelines in Canada recommend that people stay at least two metres away from others as part of physical distancing measures to curb the spread of COVID-19. (Gary Moore/CBC)

Loeb said that’s just a “signal” that part of the virus was there. 

“Does it mean that COVID-19 is spreading from person to person through aerosols? I would say definitively not,” Loeb said. 

If the virus were airborne, we’d know by now, said Dr. Allison McGeer, because every health care worker would be infected despite wearing personal protective equipment.

“You and I don’t have to worry walking down the street that we’re going to be breathing the air of somebody who walked down the street five minutes ahead of us who had COVID-19 and didn’t know it,” said McGeer, an infectious disease specialist with Sinai Health in Toronto who is leading a national research team studying how COVID-19 is transmitted. “That we can be confident about.”

Is there evidence the virus could be spread farther than 2 metres?

Some studies, including Bourouiba’s, show that droplets from coughs and sneezes can, in fact, travel much farther than expected. Bourouiba’s high-speed imaging measurements and modelling show smaller respiratory droplets don’t behave like individual droplets but are in a turbulent gas cloud trapping them and carrying them forward within it. The moist environment reduces evaporation, allowing droplets of many sizes to survive much longer and travel much farther than two metres — up to seven or eight metres, in the case of a sneeze

WATCH | Close-up view of the droplets released by a person sneezing

(Credit Lydia Bourouiba/MIT/JAMA Networks)

She said the research “is about revealing what you cannot see with the naked eye.”

A more recent Canadian study used a “cough chamber” to show that if someone coughs without covering their mouth, droplets from the cough are still travelling at a speed of about one kilometre per hour when they hit the two-metre edge of the chamber. Within the chamber, droplets remained suspended for up to three minutes. 

WATCH | The speed and distance travelled by droplets from a cough

Dr. Samira Mubareka, a virologist at Sunnybrook Hospital in Toronto who co-authored the study, said it “gives you a sense of what the possibilities are,” but noted that the researchers, who were studying flu patients, detected very little virus in the droplets.

What does that say about the 2-metre guideline?

Bourouiba says her research points to the potential for exposure beyond two metres from someone who is coughing and sneezing. As she wrote in the journal JAMA Insights in March, that means it’s “vitally important” for health care workers to wear high-grade personal protective equipment in the form of respirators even if they’re farther than two metres away from infected patients.  

However, she does think two metres can be far enough for healthy people in the general public in most environments, since breathing and talking don’t propel droplets and surrounding cloud too far.

Mubareka stands by the two-metre guideline despite the findings of her cough chamber study.

Because despite dramatic images of respiratory droplets being propelled from someone’s nose and mouth, it’s not yet clear how many of them contain virus and how many are infectious.

“And that’s really the key variable — that’s what really determines your risk,” she said. “Those are the kinds of things we haven’t been able to measure.” That may change, she added, with the recent invention of particle samplers designed specifically for viruses.

Loeb of McMaster, notes that a cough chamber and similar laboratory setups are highly artificial settings and controlled environments.

“They’re basically saying what’s theoretically possible,” he said. “I think those are provocative and those are hypothesis- generating, but then they need to be tested in the field.”

Loeb is running such a field test himself — a randomized controlled trial of the use of medical versus N95 masks among health care workers to see if there is a difference in the transmission of COVID-19.

But are coughing and sneezing all we need to worry about?

That’s a question on a lot of people’s minds, given that a growing number of studies have shown asymptomatic and pre-symptomatic transmission is possible, especially among those who live with an infected person. 

Even though researchers aren’t sure exactly how people without symptoms transmit the disease, the new evidence has prompted both U.S. and Canadian officials to suggest apparently healthy people wear masks in public to protect others — “because it prevents you from breathing or speaking moistly on them,” Prime Minister Justin Trudeau famously explained.

“People generate particles when they’re talking, singing, breathing — so you don’t have to necessarily be coughing,” Mubareka said. “It’s just that maybe the dispersion is a little bit more limited.” 

WATCH | The droplets produced when someone speaks with, and without, a mask

This video, from a study published in April 2020 the New England Journal of Medicine by researchers at the U.S. National Institutes of Health, uses laser light scattering to show droplets produced when someone speaks. 0:42 

A recent brief video and report by U.S. National Institutes of Health researchers used lasers to show that droplets projected less than 10 centimetres when someone says the phrase “Stay healthy.” It found the louder someone spoke, the more droplets were emitted.

But they were dramatically reduced if a damp washcloth — a stand-in for a mask — was placed over the speaker’s mouth.

So what about using masks to curb the spread of COVID-19?

Studies have already provided evidence that the rate at which sick people shed the virus into their surroundings is reduced when they wear a mask. 

Other studies, such as a 2009 paper in Journal of the Royal Society Interface, use imaging to show how wearing a mask while coughing reduces the jet of air that’s normally directed forward and down. A surgical mask “effectively blocks the forward momentum of the cough jet and its aerosol content,” the study found. Some does leak out the sides, top and bottom, but without much momentum.


A 2009 study by researchers in the U.S. and Singapore uses schlieren imaging to show airflow from a person’s mouth a) without a mask b) with a medical mask and c) with an N95 mask. (Gary S. Settles/Penn State University/Journal of the Royal Society Interface)

The World Health Organization recommends that people wear masks if they are coughing and sneezing or if they are caring for someone who is sick.

It notes that studies haven’t been conducted yet on whether or not transmission is reduced when healthy people wear masks in public, but it encourages countries to look into that. 

Many governments haven’t waited. Los Angeles, Italy and Austria are among the places that have begun requiring customers to wear masks while shopping


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SpaceX Will Test ‘VisorSat’ System to Make Starlink Satellites Invisible

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SpaceX is already the world’s largest single satellite operator with more than 400 of its Starlink internet nodes zipping around the Earth, but that’s only the start. The company hopes to have a fleet of thousands of satellites in just a few years, and that has astronomers worried. We’ve already seen these clouds of manmade material interfere with observations, and the problem will only get worse. SpaceX CEO Elon Musk has promised to mitigate the astronomical interference caused by the Starlink Constellation, and now we’ve got more information about the company’s “VisorSat” solution. 

Satellite internet already exists, but bandwidth and latency are inferior to what you can get with any modern terrestrial solution. This has made satellite internet a last resort for those with no other connectivity options. Key to SpaceX’s approach is the massive size of its fleet, which will provide higher bandwidth to users on the ground. Some of the Starlink constellation will also orbit at very low altitudes to cut down on latency. All this means the probes are more likely to show up in astronomical observations, some of which have to remain focused on the same patch of sky for hours at a time. In one incident from early 2020, a team from the CTIO observatory in Chile lost 15-20 percent of the data from an image of the Magellanic Clouds. 

The solution, apparently, is a system SpaceX has dubbed VisorSat. Once in orbit, the satellites would deploy small fins to block sunlight from hitting the reflective antennas and bouncing down to Earth. Musk says this should make the probes invisible to the naked eye and minimize the impact on astronomy. The company will also change the way the satellites orient themselves while moving into higher orbits after launch, which is when they are most visible. 

SpaceX launches 60 Starlink satellites with a single Falcon 9 rocket.

Previously, SpaceX experimented with treating materials to make them less reflective, and that showed promise in early testing. However, Musk says he believes VisorSat will be more effective. SpaceX intends to test VisorSat on the next Starlink launch, which could happen in the next few weeks. SpaceX has been launching batches of 60 satellites about once per month this year. 

If VisorSat works as intended, all future Starlink satellites will include the technology. SpaceX designed the satellites to be cheap with an expected lifespan of three or four years. That means the company can replace the current 400-strong fleet with less reflective satellites little by little as they fail and deorbit.

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Who's rating doctors on RateMDs? The invisible hand of 'reputation management'

This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. If you haven't subscribed yet, you can do that by clicking here.

Did that doctor pay to hide some bad reviews on RateMDs, the online physician rating system? You wouldn't know.

Nor would you know if a doctor hired a reputation management service to boost the volume of positive reviews.

Online reputation management is an emerging industry with companies offering a variety of services to professionals who find themselves ranked on rating sites with no ability to opt out and with no control over the anonymous comments that can affect their reputation.

I feel this is akin to  cyberbullying .– Dr. Sukhbir  Singh, gynecologist, The Ottawa Hospital

The fact that those reputation management tools exist came as a shock to Dr. Sukhbir Singh, a gynecologist at The Ottawa Hospital.

Singh was already grappling with a negative review posted on his RateMDs page — a posting he discovered last weekend after an anonymous person claimed he had harmed them with a procedure that he doesn't do.

He quickly responded on the site, advising the person to speak to the hospital about their concerns,

Then, just as suddenly, the posting vanished.

"This is crazy. None of this makes sense to me," he said. "I feel this is akin to cyberbullying."

In the middle of all of that a sales representative from RateMDs contacted him offering "reputation management tools" for a fee. The service includes the ability to keep up to three comments hidden from public view.

"That just made me sick to my stomach," he said. "It doesn't seem that in a public health-care system that I should be marketing myself, that I should be protecting my reputation and paying an independent private company to do that work."

RateMDs offers doctors two special plans to enhance their presence on the site. The "Promoted" package costs $ 179 US per month and includes banner ads that will appear on competing doctor's pages.

RateMDs online physician rating site sells advertising packages to doctors which allows them to pay a fee and hide some unfavourable comments. (Daniel Rofusz/CBC News)

And for $ 359 US per month the doctor can buy the "Promoted plus" option. Both packages allow doctors to hide up to three unfavourable comments — a feature called "Ratings Manager."

But if a doctor stops paying, those unfavourable ratings will reappear.

"The reviews a provider designates with the Ratings Manager are not permanently removed and their numerical scores remain as part of the calculation of a provider's overall rating," said Chris Goodridge, chief investment officer of VerticalScope Inc., the parent company of Toronto-based RateMDs. (Torstar Corp, publisher of the Toronto Star, purchased a 56 per cent ownership in VerticalScope in 2015.)

"If a user unsubscribes from the Promoted or Promoted Plus plans, he or she will no longer receive the benefits associated with that subscription," Goodridge said via email. 

"You're held a little bit to ransom because the second you stop paying that $ 200 per month, those hidden reviews come back online," said Ryan Forman, who runs a company called GlowingMDs that helps doctors manage their RateMDs profiles.

Reclaiming reputations

Forman's company advertises its service to doctors with the line: "Reclaim your reputation."

For a monthly fee of $ 229 plus HST the company provides a ratings template that doctors offer to patients to complete after an appointment.

"We then take all of those reviews, good or bad, from the doctor, and we then post it to RateMDs in effect on the doctor's behalf."

A reputation management company advertises service to physicians to boost positive patient testimonials on RateMDs online doctor rating site. (Daniel Rofusz/CBC News)

"We're not able to remove any negative reviews but what we can do is post legitimate reviews that come through the doctor and hopefully improve their RateMDs profile," said Forman.

Over at RateMDs, Goodridge said he knows that companies are selling reputation management services that target the online site.

"We're certainly aware that there are a number of companies that support health care providers in soliciting patient reviews and in assisting with posting those reviews," wrote Goodridge, adding that RateMDs has a system to disallow testimonials from suspicious sources.  

"RateMDs.com utilizes a variety of proprietary methods to identify and remove programmatically-generated reviews or reviews originating from suspicious sources."

Software circumvents filters

But Forman said RateMDs filters have not prevented his company from posting multiple patient testimonials for a single doctor.

"We have had experience where they have picked up where we are putting more than one review for a doctor from the same location but the truth is our software circumvents that," said Forman, adding he simply tweaks his software to get around the RateMDs filters.

So could anyone get the software and start posting whatever they wanted as many times as they wanted?

"Yes, I think if they were tech-savvy they probably could," Forman said." It's not software that we developed, it's software that's out there on the internet so, yeah, they could definitely do it on their own."

RateMDs is a free and open forum. That means anyone can say anything about any doctor. Just write a comment, click on each of the four rating stars and hit "Rate this doctor." The site does not ask for a name, email address or phone number.

The doctor has no control over whether he or she appears on the site and there is no way to remove their page once it's been posted.

A study published in the Journal of Medical Internet Research found that more than half of Canada's physicians have been rated on the site.

"Overall, physicians are rated positively," said study author Dr. Jessica Lui, a clinical investigator at the University of Toronto. "We did find there were differences in the likelihood of receiving a positive rating depending on what type of medicine you practiced."

Misconduct decisions not visible 

But how useful are those ratings for patients especially if there are ways for doctors to boost their positive ratings?

And right now RateMDs does not post any warnings about physicians who have been disciplined by the medical regulatory colleges.

"If a provider has active or past disciplinary actions on their file they are not visible on their RateMDs.com profiles," Goodridge wrote.

The remedies do not entirely correspond to the challenge.– Chantal Bernier, privacy and cybersecurity counsel, Dentons Canada LLP

The result? Doctors who have committed professional misconduct including sexual abuse of patients can still have glowing reviews on RateMDs.

"Providing transparency on disciplinary actions is a feature we continue to pursue on behalf of our audience," wrote Goodridge. "At the moment, the limited availability of this data from the disparate colleges does not make this practical. RateMDs.com hopes to add this information in the near future by partnering with regulatory colleges if they are willing."

There is also little transparency when it comes to anonymous accusations posted on RateMDs. Several doctors told CBC News about bad experiences including malicious postings from disgruntled employees.

And when patients do post negative reviews, the doctors pointed out that they can't tell their side of the story without breaking patient confidentiality.

Forman started GlowingMDs after seeing some of those problems emerge in the medical clinics he manages.

"There's definitely a need for the service," Forman said. "Their hands are tied in terms of what they can say and do on RateMDs"

Thorny issues

Being rated without your consent can now happen to anyone. Doctors, lawyers, dog walkers — there is nothing preventing a company from setting up an online rating site and publishing anonymous reviews in any field — comments that will circulate on the internet forever.

"There is, I think, a very real issue that has, in a way, run away on us because we do not have the laws that specifically address these situations," said Chantal Bernier, former federal privacy commissioner, now a privacy and cybersecurity counsel at Dentons Canada LLP.

"The thorny issues it presents is the reconciliation between the right to information, the obligation of accountability on one side and privacy and reputation on the other."

Bernier said there is a need to examine the legislative tools that will be required to manage those competing ethical issues.

"Right now the remedies do not entirely correspond to the challenge."

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Healing invisible wounds with the Art Cart

Every Thursday at the Centre for Addiction and Mental Health in the west end of Toronto, sterile plastic chairs are pushed aside to make way for a graffiti-covered cart stocked with paint, felt, scissors and paper.

Patients peek their heads into the otherwise grey, multi-purpose room, lured by the sound of laughter. Disposable water bottles filled with bright paints are piled around large white sheets of paper on tables as patients gather around, tools in hand. 

Art Cart CAMH

The Art Cart program employs artists who have personal experience coping with mental health or addiction issues. (Stephanie vanKampen/CBC)

The Art Cart program is run by Gifts of Light, a group funded entirely by donations that supplies patients with free hygiene products, clothing — and now, art classes. It began as a pilot project one year ago and has expanded to offer improv comedy classes, painting and drum-making. 

Sheri Stranger

Sheri Stranger developed her artistic skills as a way to deal with her own mental health struggles. (Stephanie vanKampen/CBC)

Sheri Stranger, an instructor for the Art Cart sessions, came to art as a way to deal with her own mental health struggles. 

“For me any kind of art is art therapy,” she says. “I like doing expressive arts … because you don’t have to have any art skills to do it.” 

Art Cart

The Art Cart began as a pilot project in 2016. Organizers hope to make it permanently available to patients. (Stephanie vanKampen/CBC News)

Gifts of Light manager Quinn Kirby says staff have been blown away by the results.

“It just sparks this other aspect to the treatment,” she says. “I think a lot of people can really bond over this.”

For Delroy Flowers, 40, the classes are a part of a weekly routine that he looks forward to. He says painting helps him relax and treat his schizophrenia.

“When you do it by yourself, you’re not so relaxed. But when you do it with other people, you actually grow,” he says.

Quinn Kirby

Gifts of Light manager Quinn Kirby stands in front of the Art Cart. (Stephanie vanKampen/CBC)

Staff say many of their patients rarely see visitors, so the art classes help break up the boredom. Many patients say they plan to take their new skills and the lessons that come with them and into recovery. 

“Just like life, sometimes you got to wipe it clean and start all over again,” says Stranger, as she does just that to paint on a canvas.

“See? I just learned something new,” replies Flowers.

Art Cart

Artworks created by patients are displayed inside the hospital and sold with proceeds going back into the Art Cart program. (Stephanie vanKampen/CBC)

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