Social media use driven by search for reward, akin to animals seeking food, new study shows

Our use of social media, specifically our efforts to maximize “likes,” follows a pattern of “reward learning,” concludes a new study by an international team of scientists.

Our use of social media, specifically our efforts to maximize “likes,” follows a pattern of “reward learning,” concludes a new study by an international team of scientists. Its findings, which appear in the journal Nature Communications, reveal parallels with the behavior of animals, such as rats, in seeking food rewards.

“These results establish that social media engagement follows basic, cross-species principles of reward learning,” explains David Amodio, a professor at New York University and the University of Amsterdam and one of the paper’s authors. “These findings may help us understand why social media comes to dominate daily life for many people and provide clues, borrowed from research on reward learning and addiction, to how troubling online engagement may be addressed.”

In 2020, more than four billion people spent several hours per day, on average, on platforms such as Instagram, Facebook, Twitter, and other more specialized forums. This widespread social media engagement has been likened by many to an addiction, in which people are driven to pursue positive online social feedback, such as “likes,” over direct social interaction and even basic needs like eating and drinking.

While social media usage has been studied extensively, what actually drives people to engage, sometimes obsessively, with others on social media is less clear.

To examine these motivations, the Nature Communications study, which also included scientists from Boston University, the University of Zurich, and Sweden’s Karolinska Institute, directly tested, for the first time, whether social media use can be explained by the way our minds process and learn from rewards.

To do so, the authors analyzed more than one million social media posts from over 4,000 users on Instagram and other sites. They found that people space their posts in a way that maximizes how many “likes” they receive on average: they post more frequently in response to a high rate of likes and less frequently when they receive fewer likes.

The researchers then used computational models to reveal that this pattern conforms closely to known mechanisms of reward learning, a long-established psychological concept that posits behavior may be driven and reinforced by rewards.

More specifically, their analysis suggested that social media engagement is driven by similar principles that lead non-human animals, such as rats, to maximize their food rewards in a Skinner Box—a commonly used experimental tool in which animal subjects, placed in a compartment, access food by taking certain actions (e.g., pressing a particular lever).

The researchers then corroborated these results with an online experiment, in which human participants could post funny images with phrases, or “memes,” and receive likes as feedback on an Instagram-like platform. Consistent with the study’s quantitative analysis, the results showed that people posted more often when they received more likes—on average.

“Our findings can help lead to a better understanding of why social media dominates so many people’s daily lives and can also provide leads for ways of tackling excessive online behavior,” says the University of Amsterdam’s Björn Lindström, the paper’s lead author.

More information: Andreas Olsson et al. The neural and computational systems of social learning, Nature Reviews Neuroscience (2020). DOI: 10.1038/s41583-020-0276-4Journal information:Nature Communications Nature Reviews Neuroscience

https://medicalxpress.com/news/2021-02-social-media-driven-reward-akin.html

Study identifies potential link between Soldiers exposed to blasts, Alzheimer’s

Research shows that Soldiers exposed to shockwaves from military explosives are at a higher risk for developing Alzheimer’s disease — even those that don’t have traumatic brain injuries from those blasts. A new Army-funded study identifies how those blasts affect the brain.

Researchers at the University of North Carolina at Pembroke in collaboration with the U.S. Army Combat Capabilities Development Command, now known as DEVCOM, the Army Research Laboratory, and the National Institutes of Health found that the mystery behind blast-induced neurological complications when traumatic damage is undetected may be rooted in distinct alterations to the tiny connections between neurons in the hippocampus, the part of the brain particularly involved in memory encoding and social behavior.

The research published in Brain Pathology, the medical journal of the International Society of Neuropathology, was funded by the lab’s Army Research Office.

“Blasts can lead to debilitating neurological and psychological damage but the underlying injury mechanisms are not well understood,” said Dr. Frederick Gregory, program manager, ARO. “Understanding the molecular pathophysiology of blast-induced brain injury and potential impacts on long-term brain health is extremely important to understand in order to protect the lifelong health and well-being of our service members.”

The research team tested slices of rat hippocampus by exposing the healthy tissue to controlled military blast waves. In the experimental brain explants (tissue slices maintained alive in culture dishes), the rapid blast waves produced by the detonated military explosives led to selective reductions in components of brain connections needed for memory, and the distinct electrical activity from those neuronal connections was sharply diminished.

The research showed that the blast-induced effects were evident among healthy neurons with subtle synaptic pathology, which may be an early indicator of Alzheimer’s-type pathogenesis occurring independent of overt brain damage.

“This finding may explain those many blast-exposed individuals returning from war zones with no detectable brain injury, but who still suffer from persistent neurological symptoms, including depression, headaches, irritability and memory problems,” said Dr. Ben Bahr, the William C. Friday distinguished professor of Molecular Biology and Biochemistry at UNC-Pembroke.

The researchers believe that the increased risk of developing Alzheimer’s disease is likely rooted in the disruption of neuronal communication instigated by blast exposures.

“Early detection of this measurable deterioration could improve diagnoses and treatment of recurring neuropsychiatric impediments, and reduce the risk of developing dementia and Alzheimer’s disease later in life,” Bahr said.

https://www.army.mil/article/243681/study_identifies_potential_link_between_soldiers_exposed_to_blasts_alzheimers

Artificial intelligence tool for reading MRI scans could transform prostate cancer surgery and treatment

Anant Madabhushi

Researchers at the Center for Computational Imaging and Personalized Diagnostics (CCIPD) at Case Western Reserve University have preliminarily validated an artificial intelligence (AI) tool to predict how likely the disease is to recur following surgical treatment for prostate cancer.

The tool, called RadClip, uses AI algorithms to examine a variety of data, from MRI scans to molecular information. The research team included Cleveland Clinic, University Hospitals and the Louis Stokes Cleveland Veterans Administration Medical Center.

“This tool can help urologists, oncologists and surgeons create better treatment plans so that their patients can have the most precise treatment,” said Lin Li, a doctoral student in Case Western Reserve’s Biomedical Engineering Department and a member of the CCIPD team that developed the tool. “RadClip allows physicians to evaluate the aggressiveness of the cancer and the response to treatment so they don’t overtreat or undertreat the patient.”

Li is first author on a study used to validate the tool, which appeared in January in The Lancet’s EBioMedicine journal. While other studies on prostate cancer have examined data from single sites, the CCIPD study included MRI scans from Cleveland Clinic, The Mount Sinai Hospital, University Hospitals and the Hospital of the University of Pennsylvania.

The multi-institutional study applied RadClip AI tool to pre-operative scans from nearly 200 patients whose surgeons removed their prostate gland because of cancer, then compared its results of other predictive approaches—as well as the patients’ outcomes in succeeding years.

One of the critical questions in managing prostate cancer in men undergoing surgery is identifying which are at highest risk of recurrence and prostate cancer-specific mortality so they can be identified early for additional therapy.

While RadClip has been shown to be able to predict the risk of disease recurrence, clinical trials will be needed to demonstrate that the tool can also help identify men undergoing surgery who would also benefit from additional therapy.

The approach involved using AI to identify subtle differences in heterogeneity and texture patterns inside and outside the tumor region on pre-operative MRI to predict patient outcome following surgery.       

“We’re bringing together and connecting a variety of information, from radiologic scans like MRI to digitized pathology specimen slides and genomic data, for providing a more comprehensive characterization of the disease,” said Anant Madabhushi, CCIPD director, the Donnell Institute Professor of Biomedical Engineering at Case Western Reserve and the study’s senior author.

Madabhushi added that the study demonstrates the value of imaging data, showing that RadClip provides better prognostic information than other commonly used tools, such as the Cancer of the Prostate Risk Assessment (CAPRA) score and the genomic-based Decipher® Prostate Cancer Test.

“Genomic-based tests cost several thousand dollars and involve destructive testing of the tissue,” Madabhushi said. “Prognostic predictions from an MRI scan provide a non-invasive method for making both short-term and long-term decisions on treatment.”

Data generated from the AI algorithms can be used to address two important clinical areas—prostate surgery and post-operative management. Information obtained from pre-operative MRI images can help predict the existence and extent of cancer on the margins of tumors, which would allow surgeons to make informed decisions about how much tissue to remove. Data also can predict the risk of cancer recurrence so oncologists can determine whether a patient needs adjuvant treatments after surgery, such as radiation therapy or chemotherapy.

“Having this information before surgery,” Li said, “provides surgeons and oncologists the time and space to adjust treatment plans and come up with a plan that’s best suited to the patient.”

University of Michigan shut down campus library for two days after discovering venomous spiders

Venomous spiders were found in the basement of Shapiro Undergraduate Library at the University of Michigan in January.

By Rebekah Riess and Leah Asmelash

It’s like something straight out of a nightmare — venomous spiders were found inside a University of Michigan library, causing the building to be shut down for two days last month.The “small number” of venomous Mediterranean recluse spiders were uncovered in the basement mechanical room of Shapiro Undergraduate Library in late January during a routine building check, said university spokesperson Kim Broekhuizen.Closing the library was a misunderstanding, and there haven’t been any other spider sightings since then, she said.”Based on what we all know now, library managers agree that it was a mistake to close the building and they apologize for the inconvenience to the university community,” Broekhuizen said in a statement issued Tuesday.

But the spiders have also been identified in basements and remote areas of other buildings on campus due to low occupancy. Broekhuizen said those buildings are also being treated by pest management.The Mediterranean recluse spider is a cousin to the brown recluse spider, but is even more reclusive.”As the name implies, they are reclusive and bites are extremely rare,” Anne Danielson-Francois, associate professor of biology at the University of Michigan, said. “Mediterranean recluse spiders prefer basement spaces, tunnels and other hideaways where there is a decrease in foot traffic.”Danielson-Francois worked with the school to determine the identity of the spider, after examining samples found in traps, Broekhuizen said.The University of Michigan has cautioned those working in basement areas to wear a long-sleeved shirt, hat, gloves and shoes that cover the entire foot when handling stored items, cardboard boxes, lumber or rocks.

https://www.cnn.com/2021/02/23/us/university-of-michigan-spiders-trnd/index.html

Scientists clone the first U.S. endangered species

A black-footed ferret was duplicated from the genes of an animal that died more than 30 years ago.

Scientists have cloned the first U.S. endangered species, a black-footed ferret duplicated from the genes of an animal that died over 30 years ago.

The slinky predator named Elizabeth Ann, born Dec. 10 and announced Thursday, is cute as a button. But watch out — unlike the domestic ferret foster mom who carried her into the world, she’s wild at heart.

“You might have been handling a black-footed ferret kit and then they try to take your finger off the next day,” U.S. Fish and Wildlife Service black-footed ferret recovery coordinator Pete Gober said Thursday. “She’s holding her own.”

Elizabeth Ann was born and is being raised at a Fish and Wildlife Service black-footed ferret breeding facility in Fort Collins, Colorado. She’s a genetic copy of a ferret named Willa who died in 1988 and whose remains were frozen in the early days of DNA technology.

Cloning eventually could bring back extinct species such as the passenger pigeon. For now, the technique holds promise for helping endangered species including a Mongolian wild horse that was cloned and last summer born at a Texas facility.

“Biotechnology and genomic data can really make a difference on the ground with conservation efforts,” said Ben Novak, lead scientist with Revive & Restore, a biotechnology-focused conservation nonprofit that coordinated the ferret and horse clonings.

Black-footed ferrets are a type of weasel easily recognized by dark eye markings resembling a robber’s mask. Charismatic and nocturnal, they feed exclusively on prairie dogs while living in the midst of the rodents’ sometimes vast burrow colonies.

Even before cloning, black-footed ferrets were a conservation success story. They were thought extinct — victims of habitat loss as ranchers shot and poisoned off prairie dog colonies that made rangelands less suitable for cattle — until a ranch dog named Shep brought a dead one home in Wyoming in 1981.

Scientists gathered the remaining population for a captive breeding program that has released thousands of ferrets at dozens of sites in the western U.S., Canada and Mexico since the 1990s.

Lack of genetic diversity presents an ongoing risk. All ferrets reintroduced so far are the descendants of just seven closely related animals — genetic similarity that makes today’s ferrets potentially susceptible to intestinal parasites and diseases such as sylvatic plague.

Willa could have passed along her genes the usual way, too, but a male born to her named Cody “didn’t do his job” and her lineage died out, said Gober.

When Willa died, the Wyoming Game and Fish Department sent her tissues to a “frozen zoo” run by San Diego Zoo Global that maintains cells from more than 1,100 species and subspecies worldwide. Eventually scientists may be able to modify those genes to help cloned animals survive.

Thanks to Mr. Cuomo for bringing this to the It’s Interesting community.

https://www.nbcnews.com/news/animal-news/scientists-clone-first-u-s-endangered-species-n1258310

Differences in Walking Patterns Could Predict Type of Cognitive Decline in Older Adults

Gait variability in older adults could be a predictor of cognitive decline and Alzheimer’s disease. Researchers found higher gait variability was associated with lower cognitive performance and an accurate predictor of Alzheimer’s disease.

Canadian researchers are the first to study how different patterns in the way older adults walk could more accurately diagnose different types of dementia and identify Alzheimer’s disease.

A new study by a Canadian research team, led by London researchers from Lawson Health Research Institute and Western University, evaluated the walking patterns and brain function of 500 participants currently enrolled in clinical trials. Their findings are published

today in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

“We have longstanding evidence showing that cognitive problems, such as poor memory and executive dysfunction, can be predictors of dementia. Now, we’re seeing that motor performance, specifically the way you walk, can help diagnose different types of neurodegenerative conditions,” says Dr. Manuel Montero-Odasso, Scientist at Lawson and Professor at Western’s Schulich School of Medicine & Dentistry.

Dr. Montero-Odasso is world renowned for his research on the relationship between mobility and cognitive decline in aging. Leading the Mobility, Exercise and Cognition (MEC) team in London, he is pioneering novel diagnostic approaches and treatments to prevent and combat early dementia.

This study compared gait impairments across the cognitive spectrum, including people with Subjective Cognitive Impairment, Parkinson’s Disease, Mild Cognitive Impairment, Alzheimer’s disease, Lewy body dementia and Frontotemporal dementia, as well as cognitively healthy controls.

Four independent gait patterns were identified: rhythm, pace, variability and postural control. Only high gait variability was associated with lower cognitive performance and it identified Alzheimer’s disease with 70 percent accuracy. Gait variability means the stride-to-stride fluctuations in distance and timing that happen when we walk.

“This is the first strong evidence showing that gait variability is an important marker for processes happening in areas of the brain that are linked to both cognitive impairment and motor control,” notes Dr. Frederico Perruccini-Faria, Research Assistant at Lawson and Postdoctoral Associate at Western’s Schulich School of Medicine & Dentistry, who is first author on the paper. “We’ve shown that high gait variability as a marker of this cognitive-cortical dysfunction can reliably identify Alzheimer’s disease compared to other neurodegenerative disorders.”

When cognitive-cortical dysfunction is happening, the person’s ability to perform multiple tasks at the same time is impacted, such as talking while walking or chopping vegetables while chatting with family.

Having gait variability as a motor marker for cognitive decline and different types of conditions could allow for gait assessment to be used as a clinical test, for example having patients use wearable technology. “We see gait variability being similar to an arrhythmia. Health care providers could measure it with patients in the clinic, similar to how we assess heart rhythm with electrocardiograms,” adds Dr. Montero-Odasso.

Funding: This study was primarily funded by the Canadian Consortium on Neurodegeneration in Aging (CCNA), a collaborative research program tackling the challenge of dementia and other neurodegenerative illnesses. The CCNA was supported by a grant from the Canadian Institutes of Health Research.

New study shows that migration of plant-eating dinosaurs was delayed by climate change

By Seth Borenstein

Plant-eating dinosaurs probably arrived in the Northern Hemisphere millions of years after their meat-eating cousins, a delay likely caused by climate change, a new study found.

A new way of calculating the dates of dinosaur fossils found in Greenland shows that the plant eaters, called sauropodomorphs, were about 215 million years old, according to a study in Monday’s Proceedings of the National Academy of Sciences. The fossils previously were thought to be as old as 228 million years.

That changes how scientists think about dinosaur migration.

The earliest dinosaurs all seemed to first develop in what’s now South America about 230 million years ago or longer. They then wandered north and all over the globe. The new study suggests not all dinosaurs could migrate at the same time.

So far, scientists haven’t found any example of the earliest plant-eating dinosaur family in the Northern Hemisphere that’s more than 215 million years old. One of the best examples of these is the Plateosaurus, a two-legged 23-foot (7-meter) vegetarian that weighed 8,800 pounds (4,000 kilograms).

Yet scientists find meat-eaters were pretty much worldwide by at least 220 million years ago, said Randy Irmis, a paleontologist at the University of Utah, who wasn’t part of the research.

The plant eaters “were late comers in the Northern Hemisphere,” said study lead author Dennis Kent, of Columbia University. “What took them so long?”

Kent figured out what probably happened by looking at the atmosphere and climate at the time. During the Triassic era, 230 million years ago, carbon dioxide levels were 10 times higher than now. It was a hotter world with no ice sheets at the poles and two bands of extreme deserts north and south of the equator, he said.

It was so dry in those regions that there were not enough plants for the sauropodomorphs to survive the journey, but there were enough insects that meat-eaters could, Kent said.

But then about about 215 million years ago, carbon dioxide levels briefly dropped in half and that allowed the deserts to have a bit more plant life and the sauropodomorphs were able to make the trip.

Kent and other scientists said Triassic changes in carbon dioxide levels were from volcanoes and other natural forces — unlike now, when the burning of coal, oil and natural gas are the main drivers.

Kent used changes in Earth’s magnetism in the soil to pinpoint the more exact date of the Greenland fossils. That highlighted the migration time gap, said several outside experts both in dinosaurs and and ancient climate.

Kent’s theory about climatic change being the difference in dinosaur migration “is super cool because it brings it back to contemporary issues,” said Irmis.

It also fits with some animals around today that have migratory issues that keep them away from certain climates, said Hans-Otto Portner, a climate scientist and biologist at the Alfred Wegener Institute in Germany who wasn’t part of the study.

While the study makes sense, there is one potential flaw, said University of Chicago dinosaur expert Paul Sereno: Just because no fossils of plant-eaters older than 215 million years have been found in the Northern Hemisphere, that doesn’t mean there were no sauropodomorphs. The fossils just may not have survived, he said.

https://apnews.com/article/climate-fossils-south-america-dinosaurs-climate-change-3e9865a26459f76e9c65d5102f17b240

Scientists discover new marine organisms on boulder on sea floor beneath 900 metres of ice shelf in Antarctica

The accidental discovery of marine organisms on a boulder on the sea floor beneath 900 metres (3,000ft) of Antarctic ice shelf has led scientists to rethink the limits of life on Earth.

Researchers stumbled on the life-bearing rock after sinking a borehole through nearly a kilometre of the Filchner-Ronne ice shelf on the south-eastern Weddell Sea to obtain a sediment core from the seabed.

While the boulder scuppered their chances of obtaining the core, footage from a video camera sent down the hole captured the first images of organisms stuck to a rock far beneath an ice shelf.

“It’s slightly bonkers,” said Dr Huw Griffiths, a marine biogeographer at the British Antarctic Survey. “Never in a million years would we have thought about looking for this kind of life, because we didn’t think it would be there.”

Ice shelves form when frozen water from the continent’s interior flows to the coast and floats on to the surrounding sea. As the ice flows over the land, it can pick up boulders that become embedded in the base of the ice shelf before dropping out on to the sea floor.

While surveys of Antarctic marine life have found some small mobile organisms – such as fish, worms, jellyfish and krill – far beneath ice shelves, they have never previously found stationary filter-feeders, which survive by ingesting food that falls down on them. Their absence led many scientists to suspect that the total darkness, the lack of food and the -2C temperature was too hostile for them.

Photos and video footage of the boulder show that it is home to at least two types of sponge, one of which has a long stem that opens into a head. But other organisms, which could be tube worms or stalked barnacles, also appear to be growing on the rock. Details on the discovery have been published in Frontiers in Marine Science.

The isolated boulder community lies 500 metres under the base of the ice shelf and 160 miles (260km) from the nearest open water. Because of the strong currents in the area, the food they ingest – perhaps dead plankton – is thought to be carried between 370 and 930 miles before reaching them.

“This is by far the furthest under an ice shelf that we’ve seen any of these filter-feeding animals,” said Griffiths. “These things are stuck on a rock and only get fed if something comes floating along.

“It was a real shock to find them there, a really good shock, but we can’t do DNA tests, we can’t work out what they’ve been eating, or how old they are. We don’t even know if they are new species, but they’re definitely living in a place where we wouldn’t expect them to be living,” he said.

Women better at reading minds than men, new study finds

Psychologists at the University of Bath, Cardiff, and London have developed the first ever ‘mind-reading questionnaire’ to assess how well people understand what others are really thinking.

A new approach to ‘mind-reading‘ has been developed by researchers at the University of Bath, Cardiff, and London to improve how well we understand what others are thinking. And it transpires that women are much better than men at putting themselves in someone else’s shoes.

Mind-reading, sometimes referred to in psychology as ‘mentalising’, is an important ability enabling us to pick-up on subtle behavioural cues that might indicate that someone we are speaking to is thinking something that they are not saying (e.g. being sarcastic or even lying).

The researchers say that we all have different mind-reading abilities, with some of us inherently better than others. The fact that not all of us are good at mind-reading can cause challenges—in particular for people with autism where it can lead to social struggles in building or maintaining relationships.

To identify those people who have difficulties and to provide them with appropriate support, the team at Bath designed a new mind-reading test, which draws on data from over 4,000 autistic and non-autistic people in the UK and US.

Results from their simple, four-step questionnaire were scored, ranging from 4 to 16 (with 4 indicating poor mind-reading abilities; 16 indicating excellent abilities). The average score for their questionnaire was between 12 and 13. After statistically confirming that the test was measuring the same thing in men and women, they found that females reported better mind-reading than males, whilst also confirming some of the well-reported social challenges faced by the autistic community.

Women better at reading minds than men, new study finds
Mind-reading questionnaire developed by researchers at the University of Bath.

Their method, which uses just four questions to assess individuals, is published today, along with their research findings, in the journal Psychological Assessment.

Dr. Punit Shah, senior author of the study and leading expert on social cognitive processing at the University of Bath’s Department of Psychology explained: “We will all undoubtedly have had experiences where we have felt we have not connected with other people we are talking to, where we’ve perceived that they have failed to understand us, or where things we’ve said have been taken the wrong way. Much of how we communicate relies on our understanding of what others are thinking, yet this is a surprisingly complex process that not everyone can do.

“To understand this psychological process, we needed to separate mind-reading from empathy. Mind-reading refers to understanding what other people are thinking, whereas empathy is all about understanding what others are feeling. The difference might seem subtle but is critically important and involves very different brain networks. By focussing carefully on measuring mind-reading, without confusing it with empathy, we are confident that we have just measured mind-reading. And, when doing this, we consistently find that females reported greater mind-reading abilities than their male counterparts.”

Lead researcher, Rachel Clutterbuck, emphasised the clinical importance of the questionnaire. She said: “This new test, which takes under a minute to complete, has important utility in clinical settings. It is not always obvious if someone is experiencing difficulties understanding and responding to others—and many people have learnt techniques which can reduce the appearance of social difficulties, even though these remain.

“This work has great potential to better understand the lived experience of people with mind-reading difficulties, such as those with autism, whilst producing a precise quantitative score that may be used by clinicians to identify individuals who may benefit from interventions.”

Dr. Shah added: “This research has been about understanding more about our mind-reading abilities and providing solutions to those who might struggle, particularly the autistic community. We have created a freely available questionnaire which we hope can help identify people who are experiencing mental difficulties relevant to social situations.”

https://medicalxpress.com/news/2021-02-women-minds-men.html

All the Coronavirus in the World Could Fit Inside a Coke Can, With Plenty of Room to Spare

By Christian Yates

When I was asked to calculate the total volume of SARS-CoV-2 in the world for the BBC Radio 4 show “More or Less,” I will admit I had no idea what the answer would be. My wife suggested it would be the size of an Olympic swimming pool. “Either that or a teaspoon,” she said. “It’s usually one or the other with these sorts of questions.”

So how to set about calculating an approximation of what the total volume really is? Fortunately, I have some form with these sorts of large-scale back-of-the-envelope estimations, having carried out a number of them for my book The Maths of Life and Death. Before we embark on this particular numerical journey, though, I should be clear that this is an approximation based on the most reasonable assumptions, but I will happily admit there may be places where it can be improved.

So where to start? We’d better first calculate how many SARS-CoV-2 particles there are in the world. To do that, we’ll need to know how many people are infected. (We’ll assume humans rather than animals are the most significant reservoir for the virus.)

According to stats website Our World in Data, half a million people are testing positive for Covid every day. Yet we know that many people will not be included in this count because they are asymptomatic or choose not to get tested, or because widespread testing is not readily available in their country.

Using statistical and epidemiological modeling, the Institute for Health Metrics and Evaluations has estimated that the true number of people infected each day is more like three million.

The amount of virus that each of the people currently infected will carry around with them (their viral load) depends on how long ago they were infected. On average, viral loads are thought to rise and peak about six days after infection, after which they steadily decline.

Of all the people who are infected now, those who got infected yesterday will contribute a little to the total count. Those who were infected a couple of days ago will contribute a little more. Those infected three days ago a little more still. On average, people infected six days ago will have the highest viral load. This contribution will then decline for people who were infected seven or eight or nine days ago, and so on.

The final thing we need to know is the number of virus particles people harbor at any point during their infection. Since we know roughly how viral load changes over time, it’s enough to have an estimate of the peak viral load. An unpublished study took data on the number of virus particles per gram of a range of different tissues in infected monkeys and scaled up the size of tissue to be representative of humans. Their rough estimates for peak viral loads range from 1 billion to 100 billion virus particles.

Let’s work with the higher end of the estimates so that we get an overestimate of the total volume at the end. When you add up all the contributions to the viral load of each of the three million people who became infected on each of the previous days (assuming this three million rate is roughly constant), then we find that there are roughly two quintillion (2×10¹⁸ or two billion billion) virus particles in the world at any one time.https://www.youtube.com/embed/cQQoLfOXV4E?wmode=transparent&start=0&enablejsapi=1

This sounds like a really big number, and it is. It is roughly the same as the number of grains of sand on the planet. But when calculating the total volume, we’ve got to remember that SARS-CoV-2 particles are extremely small. Estimates of the diameter range from 80 to 120 nanometers. One nanometer is a billionth of a meter. To put it in perspective, the radius of SARS-CoV-2 is roughly 1,000 times thinner than a human hair. Let’s use the average value for the diameter of 100 nanometers in our subsequent calculation.

To work out the volume of a single spherical virus particle we need to use the formula for the volume of a sphere that is, no doubt, on the tip of everyone’s tongue:

V = 4 π r³/3

Assuming a 50 nanometer radius (at the center of the estimated range) of SARS-CoV-2 for the value of r, the volume of a single virus particle works out to be 523,000 nanometres³.

Multiplying this very small volume by the very large number of particles we calculated earlier, and converting into meaningful units gives us a total volume of about 120 milliliters (ml). If we wanted to put all these virus particles together in one place, then we’d need to remember that spheres don’t pack together perfectly.

Close Sphere Packing

If you think about the pyramid of oranges you might see at the grocery store, you’ll remember that a significant portion of the space it takes up is empty. In fact, the best you can do to minimize empty space is a configuration called “close sphere packing” in which empty space takes up about 26 percent of the total volume. This increases the total gathered volume of SARS-CoV-2 particles to about 160ml, easily small enough to fit inside about six shot glasses. Even taking the upper end of the diameter estimate and accounting for the size of the spike proteins all the SARS-CoV-2 still wouldn’t fill a Coke can.

It turns out that the total volume of SARS-CoV-2 was between my wife’s rough estimates of the teaspoon and the swimming pool. It’s astonishing to think that all the trouble, the disruption, the hardship, and the loss of life that has resulted over the last year could constitute just a few mouthfuls of what would undoubtedly be the worst beverage in history.