Molecular biology’s flower child — Science News , January 6, 1973 During the past several years, some artificial genes have been synthesized…. But no one had unraveled a real gene that dictates the production of a protein. Now researchers … have done just that…. There is little doubt that sequencing of genes holds powerful ramifications for the advance of medical science.
A new era of genetics research dawned when scientists reported that they had deciphered the building blocks of a gene belonging to a virus. (The gene itself looks flowerlike when folded up.) In the decades since, scientists have rendered genetic blueprints, or genomes, for entire organisms across the tree of life.
In 2001, the Human Genome Project released a rough draft of our collective genome. The master blueprint was finally completed last year ( SN: 4/23/22, p. 6 ). Access to the human genome has led to powerful medical advances , including the development of targeted gene therapies and screenings for rare disorders ( SN: 3/27/21, p. 10 ). In the future, people may routinely have their genomes sequenced to monitor health.
Cassie Martin is an associate editor. She has a bachelor’s degree in molecular genetics from Michigan State University and a master’s degree in science journalism from Boston University.
Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
The general feeling during the pandemic was one of languishing, according to a 2021 New York Times article. But that framing speaks to the privileged few, ignoring those lower on the social totem pole, researchers say.
“Languishing is the neglected middle child of mental health. It’s the void between depression and flourishing — the absence of well-being,” wrote Grant, of the University of Pennsylvania.
The idea struck a chord with readers, and Grant’s ode to languishing went on to become the newspaper’s most read article of the year. Even I, generally suspicious of fads, felt the idea’s lure. Yes, I thought to myself, that explains a lot.
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But I began to question my gut reaction to Grant’s piece after stumbling across several articles on flourishing in the December SSM-Mental Health — all part of a series spearheaded by medical anthropologist Sarah Willen.
The study of how and why people flourish anchors a subfield of psychology known as positive psychology and includes related areas of research into happiness, well-being and resilience. In this research, flourishing refers to an optimal state of mental well-being, where one is happy, satisfied with life and has a sense of purpose.
Positive psychologists tend to believe that anyone can flourish if they just try hard enough, says Willen, of the University of Connecticut in Storrs. Consequently, she says, these researchers tend to downplay systemic barriers to flourishing, such as those related to race or class.
Positive psychologists “presume that people have a good measure of control over what they are able to do in life,” Willen says. But her own research, and that of others, shows that societal forces limit that control for many people.
In one article in the SSM-Mental Health series, Willen zooms in on Grant’s column to argue that its languishing framing speaks to the privileged few, and illustrates how the elite and powerful often capture the narrative during historic moments while eliding the lived experience of people lower on the social totem pole.
Positive psychology is a relatively young field. In the late 1990s, when psychologist Martin Seligman of the University of Pennsylvania took over as president of the American Psychological Association, he sought to reverse the field’s traditional focus on mental illness and focus instead on mental well-being. Since that time, positive psychology has emerged as a leading paradigm for research into mental health, writes Willen in her introduction to the mental health series.
The field has garnered enormous public and private investments: The Templeton Foundation, for example, currently funds the Global Flourishing Study, a $43.4 million initiative at Harvard University that will look at flourishing across time among 240,000 participants from 22 countries.
Meanwhile, the study of human flourishing and its effects has permeated well beyond psychology research. The concept now shows up frequently in research on preventive medicine and physical health , and in K-12 schools through what’s known as positive education , where, the idea goes, positive schools and positive teachers who “transmit optimism, trust and a hopeful sense of the future … are the fulcrum for producing more well-being in a culture.”
But some researchers remain skeptical of positive psychology. For one, the field largely emphasizes individual-level — not societal — changes to help people flourish, such as practicing gratitude and volunteering. That risks reducing the study of flourishing to simple self-help tricks, Willen says. What’s more, this individualized view of flourishing helps fuel the incredibly powerful and profitable self-help industry, say Willen and others.
“Positive psychology is a billion-dollar industry, and selling positivity as they do is incredibly lucrative and culturally seductive,” says Oksana Yakushko, a practicing psychologist in Santa Barbara, Calif.
But, she says, the field ignores many people’s realities. “I am troubled by the socio-political implications of selling this positive psychology ideology in a world where human beings are consistently abused, traumatized, and stressed because they are not white, wealthy, able-bodied, Western, heterosexual, etc.”
With positive psychology capturing money and attention, Willen began thinking a few years ago about how to push back against the movement. Decades of research into public health have made clear that thriving in life depends at least as much on a person’s environment and circumstances as their individual attributes, she says. “There are times in life when you feel like you just have to say something. It feels really important [to] bring a perspective from another discipline.”
So from 2018 to 2019, Willen and her team conducted a qualitative study of flourishing in Cleveland. Their 167-person pool of participants reflected the city’s economic and racial diversity. The team sought to understand how people conceived of flourishing through a series of open-ended questions beginning with: “Would you describe yourself as someone who’s flourishing at this point in your life? Why or why not?”
Roughly half of the participants said they were flourishing, the team reported in the December SSM-Mental Health. But the researchers also identified stark racial and socioeconomic disparities in those responses.
Sixty-seven percent of white respondents felt they were flourishing compared with 48 percent of Black respondents. Similarly, 88 percent of respondents with incomes over $100,000 reported flourishing compared with 46 percent of respondents with incomes below $30,000.
U.S. researchers asked 167 Midwesterners to identify factors key to flourishing. Of the top six, four (blue) are generally included in existing indices of flourishing used by positive psychologists. But over two-thirds of people identified two factors, a stable income and one’s environment (gray), that aren’t generally included. Environment, which the researchers called “social determinants of health,” includes access to food, education and safe neighborhoods. As a result, positive psychologists miss crucial material or structural circumstances that contribute to people’s well-being, the researchers say.
The team’s findings in response to another question — “What do people need, in general, to flourish?”— illuminated how participants’ understanding of flourishing often veered away from that of positive psychologists.
Positive psychologists tend to define someone as flourishing if they report having generally positive relationships and emotions, meaning and purpose in their life, self-acceptance or high self-esteem and deep engagement in their life’s activities. Among participants in Willen’s study, such relationships and feeling good about oneself were important to flourishing, but meaning and purpose showed up less frequently.
Most crucially, the participants in the study mentioned two aspects of flourishing that rarely figure into positive psychologists’ definitions of the term: Stable income and strong social determinants of health. The latter includes access to food, housing, education and safe neighborhoods while also experiencing low levels of discrimination.
If policy makers’ goal is to help as many people flourish as possible, then initiatives should focus on reducing inequality and mitigating those systemic barriers to well-being rather than more individualized measures, Willen says.
The disagreement between anthropologists and positive psychologists is largely one of world view, says Harvard University epidemiologist Tyler VanderWeele, who leads the Templeton-funded Global Flourishing Study. While Willen and her team argue that one’s environment may put happiness, or flourishing, out of reach, VanderWeele sees that world view as self-defeating.
Financial stability does comprise one of the six facets of flourishing that VanderWeele and colleagues are measuring in their global study of the concept. But for him, that facet is no more important than the other facets, which include happiness, mental and physical health, meaning and purpose, character and close social relationships.
“We do need to worry about structural conditions, financial means and trying to ensure opportunities for everyone to flourish and the means necessary for that.… [but] I don’t think those trump the other aspects of well-being,” says VanderWeele, who coauthored a rebuttal to the series in the same issue of SSM-Mental Health .
Focusing too much on factors outside any one individual’s control, such as racism or poverty, VanderWeele says, can be disempowering. Focusing on smaller factors, such as crafting one’s job to their liking or getting more involved in one’s community by joining a religious group or volunteering, meanwhile, hands that power back to the people.
This is not a debate between equals, Willen counters. With so much momentum behind their movement, positive psychologists have captured the narrative. And their self-help view of how to flourish is becoming The View, she says.
After Adam Grant’s article appeared in the Times, Willen witnessed how concepts drawn from positive psychology — in this case languishing — take on a life of their own as they enter the public domain.
That bird’s-eye view arose thanks to the Pandemic Journaling Project — an initiative Willen and other researchers launched in May 2020 to enable people from all walks of life to document how they were coping with this historic moment. Through those journal entries, the scientists observed which people glommed onto the idea that they were languishing — and who did not. Tellingly, entrants who mentioned the term skewed overwhelmingly white, wealthy and educated — a limited cohort that also reflects the readership of the Times , Willen says.
Grant uses his own arguably privileged experience of the moment to make sweeping claims about how people were experiencing the crisis, Willen says. He then uses those claims to write about how all people can overcome the blahs.
Specifically, Grant recommends people find flow. “Flow is that elusive state of absorption in a meaningful challenge or a momentary bond, where your sense of time, place and self melts away,” he writes. Such flow can arise by binge-watching shows and movies on Netflix, playing word games and, more broadly, pursuing uninterrupted time for oneself.
But just who has had the luxury to pursue such remedies for languishing, Willen asks. And who, struggling with precarity in work, health and other domains, has instead experienced something darker, something more akin to suffering?
Grant maintains that Willen is creating a “false dichotomy” between personal and systemic solutions to flourishing. Simpler behavioral interventions serve as crucial stopgap measures in challenging times, Grant adds. “It would be awfully cruel to tell readers suffering through a pandemic that they should just wait for social policies to change.”
But most people aren’t even aware of how individualized solutions to flourishing are overshadowing more systemic solutions, Willen says. Bringing that oversight to public attention is vital. “Unless we step back and ask ourselves whose voice is missing,” Willen says, “we risk internalizing a distorted account of history.”
Her words remind me of the adage: History is written by the victors. It’s a thought echoed on the Pandemic Journaling Project’s website. “Usually, history is written only by the powerful,” read the introductory words . “When the history of COVID-19 is written, let’s make sure that doesn’t happen.” That’s certainly an admonition I’ll be keeping in mind this year as I strive for balance in my reporting on positive psychology, the pandemic and other societal issues.
Sujata Gupta is the social sciences writer and is based in Burlington, Vt.
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Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Dark lightning — gamma-rays (pink in this simulated image) that result from waves of electrons (one shown, yellow) colliding with atoms in the air — may sporadically strike airplanes and briefly expose passengers to radiation, new research suggests.
NASA Goddard Space Flight Center, J. Dwyer/Florida Institute of Technology
CHICAGO — More than electricity can illuminate a thundercloud.
Brilliant bursts of gamma radiation, known as dark lightning or terrestrial gamma-ray flashes, also explode in lightning storms. And on rare occasions, those powerful blasts — the most energetic radiation to naturally arise on Earth — might even strike a passing airplane , researchers reported December 13 at the American Geophysical Union meeting. The zap could briefly expose passengers to unsafe levels of radiation.
First reported in 1994 , dark lightning is estimated to flash around the world about a thousand times each day . But scientists have only a hazy understanding of how it initiates. They generally agree dark lightning is sparked by the electric fields generated by thunderstorms and lightning bolts. These fields can spur electrons to velocities approaching the speed of light, amassing breakneck electron avalanches. When the streaming particles smash into airborne atoms, gamma radiation is unleashed.
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Dark lightning often occurs around 10 to 15 kilometers high in the sky, altitudes frequented by airlines. The new analysis combines dark lightning observations and airline routes to suggest that dark lightning might strike near a plane around once every 1 to 4 years, atmospheric scientist Mélody Pallu said at the meeting. However, that’s probably “an upper limit of the real probability,” or even 10 times the actual rate, she said, largely because the calculations didn’t factor in pilots’ avoidance of thunderstorms.
Previous computer simulations have revealed that passengers flying within 200 meters of a strong terrestrial gamma-ray flash’s initiation point may become exposed to radiation doses exceeding 0.3 sieverts , said Pallu, now at the Astroparticle and Cosmology Laboratory in Paris. Such levels would surpass the occupational safety level of 0.02 sieverts per year put forth by the International Commission on Radiological Protection.
Though somewhat nebulous, the findings make one thing clear: Further investigations are needed to figure out how dark lightning impacts passengers flying through the sky.
Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News . He has a master’s degree in geology from McGill University, and a master’s degree in science communication from the University of California, Santa Cruz.
Our mission is to provide accurate, engaging news of science to the public. That mission has never been more important than it is today.
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Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Blastomycosis, which mainly affects the lungs (illustrated here), is an infection caused by Blastomyces fungi. Such fungal infections are becoming more widespread.
KATERYNA KON/SCIENCE PHOTO LIBRARY/getty images plus
They asked about the symptoms, treatments and testing for these fungal diseases. Some, like Judy Knudsen, whose husband Jack died from a Histoplasma infection in 2020, also wrote to share their own experiences with fungal infections. Others wanted to learn more about the fungi themselves.
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I went back to Andrej Spec, a mycologist and infectious diseases doctor at Washington University School of Medicine in St. Louis whose team published the new range maps, for answers.
Spec and his colleagues are studying what has caused the fungi to spread and factors that may contribute to people getting sick. Those include changes to climate, weather patterns, extreme weather events like wildfires and floods, and even migration patterns of animals.
People generally get infected by inhaling fungal spores released during the fungi’s normal life cycle. Human activities that disturb the soil where these fungi typically live — such as farming, gardening, construction, road work or archaeology — can also stir up dust and spores.
Besides soil, bird droppings and bat guano can be sources for Histoplasma. The fungi can infect bats and grow in the animals’ intestines. Birds don’t usually carry the fungus because birds’ body temperatures are typically around 39° Celsius to 42° C (102° Fahrenheit to 107° F). “They’re too hot for Histo , but their droppings are perfectly suited to grow” the fungus, Spec says.
The highest risk to people comes when bird and bat droppings have dried out. “People will try and sweep [the droppings], and then you kick up all that dust and inhale it.” Instead of sweeping, Spec advises, “hose it down and shovel it off.”
Wearing a mask can also help limit exposure. “Especially if you’re immunosuppressed, wear a mask.”
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It is possible for the fungi to get into a cut or scrape and start an infection in the skin, but those cases are very rare, Spec says. And people generally can’t pass the infection on to others, except in very rare cases in which an infected person has donated an organ or other body tissue, he says.
These three types of fungi are known as dimorphic fungi because they have two forms. In the soil, where they normally grow, they are molds. But at 37° C — human body temperature — they shape-shift into yeast, which can grow rapidly and spread more easily in the body.
When a person inhales the fungal spores, the fungi can infect the lungs where conditions are right for it to transform. People with healthy immune systems may have no symptoms or may develop mild flulike symptoms, including fever, cough, fatigue, chills and body aches. People with coccidiomycosis — the disease caused by Coccidioides — may also get a rash on their legs or upper body.
Histoplasma, Blastomyces and Coccidioides fungi live in the soil as molds. Sometimes people breathe in spores the fungi give off as part of their natural life cycle. In the lungs, the fungi can transform into a quick-growing yeast form and cause a flulike illness, pneumonia or chronic disease. In a small number of cases, the fungi can spread to other parts of the body and cause more serious disease.
The symptoms can take time to appear. People with histoplasmosis — the disease caused by Histoplasma — can develop symptoms between three and 17 days after exposure. Symptoms of coccidiomycosis — also known as Valley Fever — appear between one and three weeks after breathing in the spores. But it can take three weeks to three months for blastomycosis — caused by Blastomyces — symptoms to start.
Mild cases usually clear up on their own in a few weeks to a few months. But some people may have lingering symptoms, especially if the infection becomes severe.
In 2019, more than 20,000 people in the United States were diagnosed with coccidiomycosis, 1,124 people had confirmed or probable cases of histoplasmosis and there were 240 cases of confirmed or probable blastomycosis, according to cases reported to the U.S. Centers for Disease Control and Prevention. That’s probably an undercount, given that mild cases likely aren’t reported and the infections can easily be misdiagnosed as more common lung diseases, the researchers say. But of the reported cases, more than half of people diagnosed with histoplasmosis and blastomycosis were hospitalized. About 5 percent of histoplasmosis patients died . So did 9 percent of those with blastomycosis.
Some people may develop severe or chronic pneumonia. And in a small number of people, the infections may spread to other parts of the body. Histoplasma “likes to go after our liver and spleen, our bone marrow … adrenal glands … and our intestines,” Spec says.
Blastomyces tends to spread to bones and joints. It may also spread to the brain where it can cause an abscess.
Coccidioides spreads in a pattern similar to Blastomyces , targeting bones, joints, skin and the brain. But instead of creating a brain abscess, the fungi cause meningitis, an inflammation of the membranes surrounding the brain and spinal cord.
“That’s with you forever if it spreads to your brain,” Spec says. “You can’t get rid of Cocci .” Doctors can manage the brain infection with antifungal drugs and give other medications to help with symptoms.
Antifungal drugs can clear most other infections. “If caught early, most people do exceedingly well,” he says.
Symptoms of all three fungal diseases caused by Histoplasma, Coccidioides and Blastomyces fungi are similar and can resemble the flu or other lung infections. Signs of a fungal lung infection may include:
People who have weakened immune systems are more likely to develop symptoms and severe disease.
And fungal infections and severe disease occur more often in men than women. About 70 percent of Blastomyces infections, 52 percent of Coccidioides cases and 56 percent of Histoplasma infections were in males, the 2019 CDC survey found.
Why males are more affected isn’t entirely clear. Some people have speculated that men tend to have more outdoor jobs and hobbies that would expose them to dirt and thus more fungi.
It’s not clear how Jack Knudsen became infected. “We have no earthly idea why this came up,” says Judy, 82, of Oklahoma City. Already battling chronic lymphocytic leukemia, heart problems and diabetes, Jack’s immune system wasn’t up to tackling the fungus. “He struggled,” she says.
He spent two weeks in the hospital getting antifungal drugs intravenously. He also took four doses a day of a liquid antifungal medication called itraconazole for the rest of his life. He died on January 23, 2020, at age 79. “We had 61 good years together,” Judy says.
There may be biological reasons for the male-female skew. A recent study of coccidiomycosis found that the sex difference was also present in nonhuman primates and in dogs . “There’s very little difference between occupational exposures and hobbies between male and female” animals, says Spec, who was not involved in that study.
The researchers found no difference in infection rates in humans up to age 19. After that, the infection rate for males held steady. But female’s infection rate dropped, Ian McHardy, a microbiologist and immunologist at Scripps Health in San Diego, and colleagues reported in the March 2022 Open Forum Infectious Diseases. That might mean that estrogen and other hormones that are usually at higher levels in females may protect against fungal infections. But that link is still speculation.
See how the ranges of Histoplasma, Blastomyces and Coccidioides have changed in the United States from 1950 to today.
Curiously, people of Filipino or African heritage may be at increased risk of developing more severe forms of Valley Fever. The reason is unknown. Other people, including those who are pregnant, living with HIV/AIDS or who have weakened immune systems from other causes are also at higher risk of more severe disease from all three fungi. So are people with diabetes and those who are older.
Because symptoms of the fungal infections so closely resemble other illnesses, it can be hard to diagnose fungal disease, Spec says.
Jack Knudsen started having seizures in 2018, Judy says. At first, doctors thought he had epilepsy, but medications to treat the disorder had no effect. When one side of his face began to droop, an MRI and other tests revealed that Jack had Histoplasma in his brain. “I had never heard of it in my life,” says Judy, who said she wanted to share her husband’s story to make people more aware of the disease.
Blood or urine tests can be used to diagnose a fungal infection. Chest X-rays or CT scans may also be used. In some cases, doctors may need take a small amount of body tissue or fluids to test for the fungi.
“A lot of people who think they have [a fungal infection] are probably going not to have it.” Spec says. “It’s a disease that is certainly more common than people think but is still relatively rare.” The new maps Spec and colleagues compiled may make doctors and other people more aware that the fungal diseases may be present where they live.
People who are concerned that they may have a fungal infection can visit mycoses.org where Spec and colleagues have assembled interactive maps showing where the fungi are found. “You’ll be able to see [based on] where you live which one you’re at risk for. When you have that data, your best goal is to talk to a doctor for testing.”
Any doctor can order a test, but infectious diseases specialists may have more expertise with the fungal diseases, he says.
Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.
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Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
Light passing through the atmospheres of planets in distant solar systems (illustrated) could reveal compounds that alien organisms might make to protect themselves from toxic elements.
SEATTLE — Attention alien hunters: If you want to find life on distant planets, try looking for signs of toxic chemical cleanup.
Gases that organisms produce as they tidy up their environments could provide clear signs of life on planets orbiting other stars , researchers announced January 9 at the American Astronomical Society meeting. All we need to do to find hints of alien life is to look for those gases in the atmospheres of those exoplanets, in images coming from the James Webb Space Telescope or other observatories that could come online soon.
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Barring an interstellar radio broadcast, the chemistry of a remote planet is one of the more promising ways that researchers could detect extraterrestrial life. On Earth, life produces lots of chemicals that alter the atmosphere: Plants churn out oxygen, for example, and a host of animals and plants release methane. Life elsewhere in the galaxy might do the same thing , leaving a chemical signature humans could detect from afar ( SN: 9/30/21 ).
But many of life’s gases are also released in processes that have nothing to do with life at all. Their detection could lead to the false impression of a living planet in a faraway solar system, when it’s really just a sterile rock.
At least one type of compound that some organisms produce to protect themselves from toxic elements, however, might provide unambiguous indications of life.
The life-affirming compounds are called methylated gases. Microbes, fungi, algae and plants are among the terrestrial organisms that create the chemicals by linking carbon and hydrogen atoms to toxic materials such as chlorine or bromine. The resulting compounds evaporate, sweeping the deadly elements away.
The fact that living creatures almost always have a hand in making methylated gases means the presence of the compounds in a planet’s atmosphere would be a strong sign of life of some kind, planetary astrobiologist Michaela Leung of the University of California, Riverside said at the meeting.
The same isn’t true of oxygen and methane. Oxygen, in particular, can accumulate when a hot star warms a planet’s oceans. “You have a steam atmosphere, and the [ultraviolet] radiation from the star splits up the water” into its constituent parts, oxygen and hydrogen, Leung says. Hydrogen is light, so much of it is lost to space on small planets. “What you have left is all of this oxygen,” which, she says, leads to “really convincing oxygen signals in this process that at no point involved life.”
Similarly, while living organisms produce methane in abundance, lifeless geological phenomena like volcanoes do too.
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At the concentrations of methylated gases typical of Earth, these gases will be hard to see in the atmospheres of distant planets, even with an instrument as powerful as the Webb telescope ( SN: 12/20/22 ). But Leung has reason to believe there may be planets where the gas abundance is thousands of times that of Earth.
“The most productive environments [for releasing methylated gases] that we see here on Earth,” she says, “are things like estuaries and wetlands.” A watery planet with lots of small continents and correspondingly more coastline, for example, could be packed with organisms cleaning away toxic chemicals with methylated gases.
One of the benefits of looking for the compounds as a sign of life is that it doesn’t require that the life resembles anything like what we have on our planet. “Maybe it’s not DNA-based, maybe it has other weird chemistry going on,” Leung says. But by assuming chlorine and bromine are likely to be toxic generally, methylated gases offer what Leung calls an agnostic biosignature, which can tell us that something is alive on a planet even if it’s utterly alien to us.
“The more signs of life we know to look for, then the better our chances of recognizing life when we do encounter it,” says Vikki Meadows, an astrobiologist at the University of Washington in Seattle who was not involved with the study. “It also helps us understand what kind of telescopes we should build, what we should look for and what the instrument requirements should be. Michaela’s work is really important for that reason.”
James Riordon is a freelance science writer who covers physics, math, astronomy and occasional lifestyle stories.
Our mission is to provide accurate, engaging news of science to the public. That mission has never been more important than it is today.
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Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).
In winter, cases of colds, flu and COVID-19 often peak. Low temperatures and humidity are partly to blame.
invincible_bulldog/iStock/Getty Images Plus
When bitter winds blew and temperatures dropped, my grandmother would urge me to come inside. “You’ll catch your death of cold out there,” she’d say.
Sure, freezing to death is possible in frigid temperatures. But doctors and other health experts have long stressed that being cold won’t give you a cold. Still, winter is undisputedly cold-and-flu season. It’s also a period when COVID-19 spreads more.
But if the chill doesn’t matter, why does the spread of so many respiratory viruses peak during the season?
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“I’ve spent the past 13 years looking into this question,” says Linsey Marr, a civil and environmental engineer at Virginia Tech in Blacksburg who studies viruses in the air. “The deeper we go, the more I realize we don’t know [and] the more there is to figure out.”
She and I are not alone. “That wintertime seasonality has puzzled people for a very long time; thousands of years, to be honest,” says Jeffrey Shaman, an infectious diseases researcher who directs the Climate and Health Program at the Columbia University Mailman School of Public Health.
There is some evidence that winter’s shorter days may make people more susceptible to infection, he says. Less sunlight means people make less vitamin D, which is required for some immune responses. But that’s just one piece of the puzzle.
Scientists are also looking at what other factors may play a role in making winter a sickening season.
My grandma’s well-intentioned urging to come in from the cold may have instead increased the risk that I’d get sick.
Colds, influenza and respiratory syncytial virus, or RSV, are all illnesses that are more prevalent at certain times of year when people spend more time inside. That includes winter in temperate climates, where there are distinct seasons, and rainy seasons in tropical zones. COVID-19 also spreads more indoors than outside ( SN: 6/18/20 ).
“When you’re outdoors, you’re in the ultimate well-ventilated space,” says David Fisman, an epidemiologist at the University of Toronto Dalla Lana School of Public Health. Viruses exhaled outside are diluted quickly with clean air.
But inside, aerosols and the viruses they contain can build up. “When you’re in a poorly ventilated space, the air you breathe in is often air that other people have breathed out,” he says.
Since viruses come along with that exhaled breath, “it makes a lot of sense that proximity to individuals who might be contagious would facilitate transmission,” Shaman says.
But there is more to the story, says Benjamin Bleier, a specialist for sinus and nasal disorders at Harvard Medical School.
“In modern society, we’re indoors all year round,” he says.
To drive the seasonal pattern we see year after year, something else must be going on too to make people more susceptible to infection and increase the amount of virus circulating, he says.
Some viruses thrive in winter. But the reason why may not be so much about temperature, but humidity.
“There are some viruses that like it warm and wet, and some viruses like it dry and cold,” says Donald Milton, an aerobiologist at the University of Maryland School of Public Health in College Park. For instance, rhinoviruses — one of the many types of viruses that cause colds — survive better when it is humid. Cases of rhinovirus infection typically peak in early fall, he says.
Marr and other researchers have found that viruses that surge in the winter, including influenza viruses and SARS-CoV-2 — the coronavirus that causes COVID-19 — survive best when the relative humidity in the air falls below about 40 percent.
Viruses aren’t usually floating around naked, Marr says. They are encased in droplets of fluid, such as saliva. Those droplets also have bits of mucus, proteins, salt and other substances in them. Those other components may determine if the virus survives drying.
When the humidity is higher, droplets dry slowly. Such slow drying kills viruses such as influenza A and SARS-CoV-2, Marr and colleagues reported July 27 in a preprint at bioRxiv.org. During slow drying, salt and other things that may harm the virus become more concentrated, although researchers still don’t fully understand what’s happening at the molecular scale to inactivate the virus.
But flash drying in parched air preserves those viruses. “If the air is very dry, the water quickly evaporates. Everything is dried down, and it’s almost like things are frozen in place,” Marr says.
At low humidity levels, airborne droplets, or aerosols, dry quickly (left), preserving viruses under a feathery crystalline lattice, as this microscope image shows. At intermediate humidity levels, crystals form inside liquid droplets (middle), but those crystals may inactivate viruses, not preserve them. At high humidity levels (right), aerosols remain liquid, allowing viruses to survive better than at midlevel humidity.
Dryer, smaller aerosols are also more buoyant and may hang in the air longer, increasing the chance that someone will breathe them in, Fisman says.
What’s more, dry air can tear down some of people’s defenses against viruses. Studies in animals suggest that dry air can trigger death of some cells lining the airways. That could leave cracks where viruses can invade.
Mucus in the airways can trap viruses and help protect against infection. But breathing cold, dry air can also slow the system that usually moves mucus out of the body. That may give viruses time to break out of the mucus trap and invade cells, Fisman says.
Being cold may not give you a cold, but it could make you more susceptible to catching one.
Normally, the immune system has a trick for warding off viruses, Bleier and colleagues recently discovered. Cells in the nose and elsewhere in the body are studded with surface proteins that can detect viruses. When one of these sensor proteins sees a virus coming, it signals the cell to release tiny bubbles called extracellular vesicles.
The bubbles work as a diversionary tactic, a bit like chaff being released from a military jet trying to avoid a heat-seeking missile, Bleier says. Viruses may go after the vesicles instead of infecting cells.
If a virus docks with one of the bubbles, it’s in for a surprise: Inside the vesicles are virus-killing bits of RNA called microRNAs. One of those microRNAs known as miR-17 could kill two types of rhinoviruses and a cold-causing coronavirus, the team reported December 6 in the Journal of Allergy and Clinical Immunology .
The immune system has a diversionary tactic to keep viruses from infecting cells in the nose: When viruses (black and gray spheres) are detected, nasal cells release bubbles called extracellular vesicles (blue circles). These bubbles are studded with proteins (red, blue and black shapes on blue circles) that are normally found on the surface of nasal cells. Viruses may go after the bubbles instead of infecting cells. When temperatures in the nose drop below body temperature (right), cells release fewer bubbles, making it easier for viruses to find and infect nasal cells.
Researchers measured bubbles released from human nasal cells grown in lab dishes at 37° Celsius, our typical body temperature. Then the scientists lowered the thermostat to 32° C. Cells released about 42 percent fewer vesicles at the cooler temperature, the team found. What’s more, those vesicles carried fewer weapons. Vesicles can pack in about 24 percent more microRNA at body temperature than when it is cooler.
I asked the experts what people can do to protect themselves from viruses in the winter. Some said using a humidifier might help raise moisture levels enough to slow the drying of virus-laden droplets, killing the viruses.
“Any increase in humidity should be beneficial,” says Shaman. “You get a lot of bang for your buck if you go from very dry to dry.”
But Milton doesn’t think it’s a good idea to pump a lot of moisture into a house when it is cold outside. “That humidity is going to find all of the cold spaces in your house and condense there,” creating a breeding ground for mold and rot, he says.
Instead, he advocates turning on kitchen and bathroom exhaust fans to increase ventilation and to use HEPA filters or Corsi-Rosenthal boxes to filter unwanted viruses out of the air ( SN: 7/25/22 ).
Bleier suggests wearing a mask. Not only can masks filter out viruses, but “our work suggests these masks have a second mechanism of action,” he says. “They keep a cushion of warm [moist] air in front of our noses, which could help bolster the immune system.”
M. Moriyama, W.J. Hugentobler and A. Iwasaki. Seasonality of respiratory viral infections. Annual Review of Virology . Vol. 7, September 2020, p. 83. doi: 10.1146/annurev-virology-012420-022445
Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.
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