Publisher Health

With an artificial intelligence (AI) method developed by researchers at Aalto University and University of Helsinki, researchers can now link immune cells to their targets and, for example, uncouple which white blood cells recognize SARS-CoV-2. The developed tool has broad applications in understanding the function of the immune system in infections, autoimmune disorders, and cancer.
The human immune defense is based on the ability of white blood cells to accurately identify disease-causing pathogens and to initiate a defense reaction against them. The immune defense is able to recall the pathogens it has encountered previously, on which, for example, the effectiveness of vaccines is based. Thus, the immune defense the most accurate patient record system that carries a history of all pathogens an individual has faced. This information however has previously been difficult to obtain from patient samples.
The learning immune system can be roughly divided into two parts, of which B cells are responsible for producing antibodies against pathogens, while T cells are responsible for destroying their targets. The measurement of antibodies by traditional laboratory methods is relatively simple, which is why antibodies already have several uses in healthcare.
“Although it is known that the role of T cells in the defense response against for example viruses and cancer is essential, identifying the targets of T cells has been difficult despite extensive research,” says Satu Mustjoki, Professor of Translational Hematology.
AI helps to identify new key-lock pairs
T cells identify their targets in a key and a lock principle, where the key is the T cell receptor on the surface of the T cell and the key is the protein presented on the surface of an infected cell. An individual is estimated to carry more different T cell keys than there are stars in the Milky Way, making the mapping of T cell targets with laboratory techniques cumbersome.

A new molecular ‘freeze frame’ technique has allowed WEHI researchers to see key steps in how the protein MLKL kills cells.
Small proteins called ‘monobodies’ were used to freeze MLKL at different stages as it moved from a dormant to an activated state, a key process that enables an inflammatory form of cell death called necroptosis. The team were able to map how the three-dimensional structure of MLKL changed, revealing potential target sites that might be targets for drugs — a potential new approach to blocking necroptosis as a treatment for inflammatory diseases.
The research, which was published in Nature Communications, was led by Associate Professor James Murphy and PhD students Ms Sarah Garnish and Mr Yanxiang Meng, in collaboration with Assistant Professor Akiko Koide and Professor Shohei Koide from New York University, US.
At a glance The ‘executioner’ protein MLKL kills cells through an inflammatory process called necroptosis. Monobody technology has enabled WEHI researchers to capture different forms of MLKL as it becomes activated and moves to kill the cell. Understanding how the three-dimensional shape of MLKL changes may lead to the development of drugs that prevent necroptosis, as a treatment for inflammatory diseases.Key steps in necroptosis
MLKL is a key protein in necroptosis, being the ‘executioner’ that kills cells by making irreparable holes in their exterior cell membrane. This allows the cell contents to leak out and triggers inflammation — alerting nearby cells to a threat, such as an infection.

An increasing number of young women are at increased risk of having children born with impaired neurological conditions, due to poor iodine intake.
Dietary changes, including a growing trend towards the avoidance of bread and iodised salt, as well as a reduced intake of animal products containing iodine can contribute to low iodine levels.
A small pilot study undertaken by the University of South Australia (UniSA) comparing iodine levels between 31 vegan/plant-based participants and 26 omnivores has flagged the potential health risk.
Urine samples showed iodine readings of 44 ug/L in the plant-based group, compared to the meat eaters’ 64 ug/L level. Neither group came close to the World Health Organization’s recommended 100 grams per litre.
Participants from both groups who chose pink or Himalayan salt instead of iodised salt had severely deficient iodine levels, averaging 23 ug/L.
The findings have been published in the International Journal of Environmental Research and Public Health.

Vigorous and rapid air exchanges might not always be a good thing when it comes to addressing levels of coronavirus particles in a multiroom building, according to a new modeling study.
The study suggests that, in a multiroom building, rapid air exchanges can spread the virus rapidly from the source room into other rooms at high concentrations. Particle levels spike in adjacent rooms within 30 minutes and can remain elevated for up to approximately 90 minutes.
The findings, published online in final form April 15 in the journal Building and Environment, come from a team of researchers at the U.S. Department of Energy’s Pacific Northwest National Laboratory. The team includes building and HVAC experts as well as experts in aerosol particles and viral materials.
“Most studies have looked at particle levels in just one room, and for a one-room building, increased ventilation is always useful to reducing their concentration,” said Leonard Pease, lead author of the study. “But for a building with more than one room, air exchanges can pose a risk in the adjacent rooms by elevating virus concentrations more quickly than would otherwise occur.
“To understand what’s happening, consider how secondhand smoke is distributed throughout a building. Near the source, air exchange reduces the smoke near the person but can distribute the smoke at lower levels into nearby rooms,” Pease added. “The risk is not zero, for any respiratory disease.”
The team modeled the spread of particles similar to SARS-CoV-2, the virus that causes COVID-19, via air-handling systems. Scientists modeled what happens after a person has a five-minute coughing bout in one room of a three-room small office building, running simulations with particles of five microns.

People with abdominal obesity and excess fat around the body’s mid-section and organs have an increased risk of heart disease even if their body mass index (BMI) measurement is within a healthy weight range, according to a new Scientific Statement from the American Heart Association published today in the Association’s flagship journal, Circulation.
“This scientific statement provides the most recent research and information on the relationship between obesity and obesity treatment in coronary heart disease, heart failure and arrhythmias,” said Tiffany M. Powell-Wiley, M.D., M.P.H., FAHA, chair of the writing committee and a Stadtman Tenure-Track Investigator and chief of the Social Determinants of Obesity and Cardiovascular Risk Laboratory in the Division of Intramural Research at the National Heart, Lung, and Blood Institute at the National Institutes of Health in Bethesda, Maryland. “The timing of this information is important because the obesity epidemic contributes significantly to the global burden of cardiovascular disease and numerous chronic health conditions that also impact heart disease.”
A greater understanding of obesity and its impact on cardiovascular health highlights abdominal obesity, sometimes referred to as visceral adipose tissue, or VAT, as a cardiovascular disease risk marker. VAT is commonly determined by waist circumference, the ratio of waist circumference to height (taking body size into account) or waist-to-hip ratio, which has been shown to predict cardiovascular death independent of BMI.
Experts recommend both abdominal measurement and BMI be assessed during regular health care visits because a high waist circumference or low waist-to-hip ratio, even in healthy weight individuals, could mean an increased risk of heart disease. Abdominal obesity is also linked to fat accumulation around the liver that often leads to non-alcoholic fatty liver disease, which adds to cardiovascular disease risk.
“Studies that have examined the relationship between abdominal fat and cardiovascular outcomes confirm that visceral fat is a clear health hazard,” said Powell-Wiley.
The risk-inducing power of abdominal obesity is so strong that in people who are overweight or have obesity based on BMI, low levels of fat tissue around their midsection and organs could still indicate lower cardiovascular disease risks. This concept, referred to as “metabolically healthy obesity,” seems to differ depending on race/ethnicity and sex.

By cracking open a cellular membrane, Northwestern University synthetic biologists have discovered a new way to increase production yields of protein-based vaccines by five-fold, significantly broadening access to potentially lifesaving medicines.
In February, the researchers introduced a new biomanufacturing platform that can quickly make shelf-stable vaccines at the point of care, ensuring they will not go to waste due to errors in transportation or storage. In its new study, the team discovered that enriching cell-free extracts with cellular membranes — the components needed to made conjugate vaccines — vastly increased yields of its freeze-dried platform.
The work sets the stage to rapidly make medicines that address rising antibiotic-resistant bacteria as well as new viruses at 40,000 doses per liter per day, costing about $1 per dose. At that rate, the team could use a 1,000-liter reactor (about the size of a large garden waste bag) to generate 40 million doses per day, reaching 1 billion doses in less than a month.
“Certainly, in the time of COVID-19, we have all realized how important it is to be able to make medicines when and where we need them,” said Northwestern’s Michael Jewett, who led the study. “This work will transform how vaccines are made, including for bio-readiness and pandemic response.”
The research will be published April 21 in the journal Nature Communications.
Jewett is a professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering and director of Northwestern’s Center for Synthetic Biology. Jasmine Hershewe and Katherine Warfel, both graduate students in Jewett’s laboratory, are co-first authors of the paper.
The new manufacturing platform — called in vitro conjugate vaccine expression (iVAX) — is made possible by cell-free synthetic biology, a process in which researchers remove a cell’s outer wall (or membrane) and repurpose its internal machinery. The researchers then put this repurposed machinery into a test tube and freeze-dry it. Adding water sets off a chemical reaction that activates the cell-free system, turning it into a catalyst for making usable medicine when and where it’s needed. Remaining shelf-stable for six months or longer, the platform eliminates the need for complicated supply chains and extreme refrigeration, making it a powerful tool for remote or low-resource settings.
In a previous study, Jewett’s team used the iVAX platform to produce conjugate vaccines to protect against bacterial infections. At the time, they repurposed molecular machinery from Escherichia coli to make one dose of vaccine in an hour, costing about $5 per dose.
“It was still too expensive, and the yields were not high enough,” Jewett said. “We set a goal to reach $1 per dose and reached that goal here. By increasing yields and lowering costs, we thought we might be able to facilitate greater access to lifesaving medicines.”
Jewett and his team discovered that the key to reaching that goal lay within the cell’s membrane, which is typically discarded in cell-free synthetic biology. When broken apart, membranes naturally reassemble into vesicles, spherical structures that carry important molecular information. The researchers characterized these vesicles and found that increasing vesicle concentration could be useful in making components for protein therapeutics such as conjugate vaccines, which work by attaching a sugar unit — that is unique to a pathogen — to a carrier protein. By learning to recognize that protein as a foreign substance, the body knows how to mount an immune response to attack it when encountered again.
Attaching this sugar to the carrier protein, however, is a difficult, complex process. The researchers found that the cell’s membrane contained machinery that enabled the sugar to more easily attach to the proteins. By enriching vaccine extracts with this membrane-bound machinery, the researchers significantly increased yields of usable vaccine doses.
“For a variety of organisms, close to 30% of the genome is used to encode membrane proteins,” said study co-author Neha Kamat, who is an assistant professor of biomedical engineering at McCormick and an expert on cell membranes. “Membrane proteins are a really important part of life. By learning how to use membrane proteins effectively, we can really advance cell-free systems.”
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Materials provided by Northwestern University. Original written by Amanda Morris. Note: Content may be edited for style and length.

Although colorectal cancer is the second most frequent cause of cancer-related death in the United States, about one-third of eligible American adults have never completed a colorectal cancer screening test, explained lead author Zhu. Zhu added that colorectal cancer screening is particularly underutilized by individuals experiencing socioeconomic disadvantages, racial and ethnic minorities, and certain age groups.
The U.S. Preventive Services Task Force (USPSTF) recommends several colorectal cancer screening methods for adults ages 50 to 75 with an average risk for this disease, and the USPSTF draft guideline update released in October 2020 recommends lowering the age of screening initiation to 45. The three most common tests are an annual fecal immunochemical test or fecal occult blood test (FIT/FOBT) that detects blood in the stool; the multitarget stool DNA (mt-sDNA) test (Cologuard), completed every three years, which detects altered DNA from cancer cells, precancerous polyps, or blood in the stool; and a colonoscopy every 10 years, which involves a gastroenterologist examining the colon with a camera and removing any precancerous polyps while a patient is under sedation.
“Previous research has shown that fewer patients complete colorectal cancer screening when only colonoscopy is recommended compared to when stool-based options are also recommended,” said Zhu.
In this study, Zhu and colleagues evaluated patient preferences for colorectal cancer screening through a survey conducted in collaboration with the National Opinion Research Center at the University of Chicago. The survey included short descriptions of FIT/FOBT, mt-sDNA, and colonoscopy, and asked a nationally representative sample of adults ages 40 to 75 to choose between two options presented at a time. A total of 1,595 respondents completed the survey. The researchers focused their analysis on a subgroup of 1,062 respondents aged 45 to 75 with an average risk of colorectal cancer.
When presented with a choice, 66 percent of respondents said they preferred mt-sDNA over colonoscopy, and 61 percent said they preferred FIT/FOBT over colonoscopy. When asked to choose between the two stool-based options, 67 percent indicated a preference for mt-sDNA over FIT/FOBT.
The investigators also examined differences in patient preferences across sociodemographic characteristics, access to health care, awareness of colorectal cancer screening, and prior experience completing a test. While mt-sDNA was preferred over colonoscopy for all age groups examined, a larger proportion of older adults (ages 65 to 75 years) said they preferred colonoscopy compared to those in younger age groups (ages 45 to 54 years).
Similarly, the preference for mt-sDNA over colonoscopy was higher among non-Hispanic white individuals compared with non-Hispanic Black and Hispanic individuals. Half of Hispanic and non-Hispanic Black respondents preferred stool-based tests over colonoscopy, with a preference for mt-sDNA over FIT/FOBT. Zhu said the observed differences among age and racial/ethnic groups might have reflected variations in preferences or disparities in access to information about newer testing methods.
Respondents without insurance were 2.5 times more likely to prefer less expensive stool-based tests over colonoscopy. The overall awareness of stool-based tests was about 60 percent, compared to 90 percent for colonoscopy, indicating that there is an opportunity to improve patient education about stool-based options, Zhu noted. Study participants who were aware of stool-based tests were two times more likely to prefer mt-sDNA over FIT/FOBT, and those who had previously had a stool-based test were 2.8 times more likely to choose FIT/FOBT over colonoscopy. By contrast, those who had previously had a colonoscopy were less than half as likely to prefer a stool-based test over colonoscopy and those who had a provider recommend colonoscopy in the past 12 months were 40 percent less likely to prefer mt-sDNA over colonoscopy.
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Despite the urgent need for treatments to slow or stop Alzheimer’s disease, finding patients for clinical trials has been difficult and frustrating.Patients are often older. Their doctors may not be part of a research network. And many with dementia never get a diagnosis — their doctors do not tell them what is wrong or they avoid finding out that they have the dreaded disease.“How do you recruit when patients do not realize they are eligible?” said Michelle Papka, director of the Cognitive and Research Center, a clinical trial site in Springfield, N.J.Her center is one of 290 now seeking participants for a new study by the drugmaker Eli Lilly and Company that plans to enroll 1,500 patients. The company hopes it will confirm results from its smaller study, lasting 76 weeks, of 257 patients. It found the experimental drug donanemab significantly slowed the progress of Alzheimer’s — the first time a study of a disease-modifying Alzheimer’s drug met its primary goals.“I will be shocked if it is not a popular study,” said John Dwyer, president of the Global Alzheimer’s Platform Foundation, a network of clinical trial sites hired by Lilly to help speed the recruitment of patients.But where will patients come from?They have to have just the right amount of brain deterioration — too much and it probably is too late. Too little and it may take too long to see a drug effect, if there is any. They often have to find out about the study on their own. They have to agree to have regular infusions of what might be a placebo for more than a year.On top of all that, if they or their family members have been paying attention to the state of Alzhemier’s drug research, they would know that study after study of what looked like a promising treatment for Alzheimer’s has failed, to such an extent that some companies, after spending billions in futile attempts, decided to get out of the business of developing Alzheimer’s drugs.Three who arrived at a clinical trial site in New Jersey on March 26, a misty Friday morning provide some answers about who might enroll, and why.HE SAID, “NO WAY, NOT ME”Michael Gross, a lifelong Yankees fan, was unnerved when he forgot the name of one of the team’s former managers — Casey Stengel — and was determined to keep it in his memory.Jackie Molloy for The New York TimesA few years ago, Michael Gross, 73, of Mahwah, N.J., began to realize something was wrong. “I was confused about words,” he said, “and it continued to get worse.”But Mr. Gross, the retired head of an advertising agency, was taken aback when a doctor suggested a spinal tap to look for proteins that are a sign of Alzheimer’s. He could not have that disease, Mr. Gross thought.“I said, ‘No way, not me,’” he said.But he did.He wept, he despaired.Then he asked, What could he do about it?He switched to the Mediterranean diet. He started exercising. He began doing crossword puzzles and subscribed to a challenging brain-training program. He found a study in mice claiming a bright light shined at their heads helped with Alzheimer’s. He bought the light.The disease kept progressing. Now he cannot remember the details of a news story as he reads it.Mr. Gross, a lifelong Yankees fan, was unnerved the day he forgot the name of the team’s former manager, Casey Stengel, and became determined to keep it in his memory.“Every day I wake up and tell myself ‘Casey Stengel, Casey Stengel,’” he says.Then he forgot the word “sardines,” a staple of his Mediterranean diet. “For a week I said to myself, ‘sardines, sardines,’” Mr. Gross said.But what he really wanted was a treatment powerful enough to stop Alzheimer’s in its tracks.Mr. Gross saw an ad on Facebook for the Lilly clinical trial. That Friday morning he arrived for a test to see if he was eligible. It consisted of a brain scan for a protein, tau, that is found in dead and dying brain neurons. If he had too little tau, he would not be eligible.He had another test, an M.R.I. scan of his brain and discovered that he was accepted for the trial.And now, if he does not get the drug? Or if the drug fails?Then he will look for other trials, Mr. Gross said. He would even consider a treatment he recently heard about. “They shoot something into your nostril, and it supposedly cures you,” he said.His wife, Peggy, chimed in.“We haven’t gotten to a point where we admitted there is no help for him,” she said.“IT GOT TO A POINT WHERE IT WAS VERY, VERY REAL”The next patient to arrive was a 63-year-old woman who is enrolled in the trial and has already had two infusions of either the drug or the placebo. She and her husband asked that their names not be used because they have not yet revealed her diagnosis to their friends and family.She’s a bubbly optimist, but because of her disease, let her husband do most of the talking. When her memory started faltering a few years ago, she and her husband attributed it to the stress of her job as an occupational therapist.“I don’t think we thought about Alzheimer’s,” her husband said.But her memory problems continued, even after she left her job. She would go grocery shopping, taking a list with her, and forget things on the list. She would forget appointments.“It got to a point where it was very, very real,” her husband said.Dr. Michelle Papka, the director of the Cognitive and Research Center in New Jersey. “How do you recruit when patients do not realize they are eligible?” she said of the difficulty in finding participants for clinical trials of Alzheimer’s drugs.Jackie Molloy for The New York TimesHe took his wife to a neurologist who administered a battery of tests. The results were not good.“For the first time it went from a memory issue to something alarming,” the husband said. On March 6, a spinal tap confirmed the likely diagnosis: Alzheimer’s.The man and his wife were distraught. No drug, no lifestyle change, had been shown to alter the course of the disease. Their doctor did not refer them to a clinical trial, but their oldest son, a second-year medical student, found the Lilly trial for them.The woman does not expect a cure, but she said, “I hope I don’t decline any farther. I don’t want to turn into a babbling idiot. If I can stay like this, I would be happy. I crochet, I color, I walk the dog.”Her husband tries not to think of the future.“I don’t know if I am in denial or what, but I haven’t fully grasped what life will be like five, 10 years down the road.”“THERE WOULDN’T BE A COVID VACCINE IF PEOPLE HAD NOT VOLUNTEERED”Marlene Lippman and Bob Lippman outside their home in Summit, N.J. Bob Lippman is a patient of a new Alzheimer’s clinical trial.Jackie Molloy for The New York TimesBob Lippman, 78, of Summit, N.J., got his Alzheimer’s diagnosis in November 2017 after a year and a half of mounting symptoms. He learned about the Lilly trial from Dr. Papka and was accepted. He had his second infusion at the New Jersey center that Friday morning.Conversation is difficult for Mr. Lippman now, so his wife, Marlene, told his story.“He was repeating things a lot and asking me the same things over and over,” she said. “He was forgetting whole conversations. At first I thought it was normal aging.”But after she heard a speaker from the Alzheimer’s Association at Sage Eldercare, a nonprofit organization near their home in Summit, N.J., she realized that what her husband was experiencing was not normal.Memory tests confirmed those fears, and a brain scan that detects amyloid, the stiff balls of plaque that are the hallmark of Alzheimer’s disease, cinched the diagnosis.It was life-shattering news.“Bob had a very strong intellect,” Ms. Lippman said. “It is hard that that part of him is being attacked.”She started making plans — redoing wills and power of attorney. She found a support group for caregivers at Sage. And she found the Lilly trial.Ms. Lippman is cleareyed about what to expect. If her husband is getting the drug and not the placebo and if the drug is as effective as it was in the initial small study, “at best it might delay the course of his decline,” she said. “It certainly is not going to cure him.”“Our main incentive is to help other people and to move research forward,” Ms. Lippman added. “There wouldn’t be a Covid vaccine if people had not volunteered.”Bob and Marlene Lippman in their home. “Bob had a very strong intellect,” Ms. Lippman said. “It is hard that that part of him is being attacked.”Jackie Molloy for The New York Times

Science shows that the risk of viral transmission outside is very low. The “two-out-of-three rule” can help you decide whether to mask up.As more people get vaccinated and spring weather and sunshine beckon us outdoors, one question may be nagging at you: Do we still need to wear masks outside?More than a year into pandemic life, many people remain confused about the risk of spending time outdoors around other people. A growing body of research shows that transmission of Covid-19 is far less likely outdoors than inside, and the risk will get even lower as more people get vaccinated and cases continue to decline. But many states have yet to lift strict outdoor mask mandates. In Massachusetts, for instance, outdoor masking is required at all times, even when nobody else is around.Recently the online magazine Slate stirred controversy when it suggested an end to outdoor mask rules. The article won support from top public health experts and even The New England Journal of Medicine blog but prompted a fierce backlash from readers, who noted that while the risk of outdoor transmission may be low, it’s not zero.“Shallow and selfish take,” wrote one reader on Twitter. “You have blood on your hands. You should feel ashamed,” posted another.After a year in which many of us have learned to dutifully wear masks and look askance at anyone who does not, it’s understandable that people remain fearful when they cross paths with the unmasked. So how do you make the right decision about when to wear a mask outside?Many virus and public health experts say the guidance hasn’t changed — spending time with others outside during the pandemic has always been safer than indoors. But whether a mask is needed outdoors depends on the circumstances, including local public health rules. Brief encounters with an unmasked person passing you on the sidewalk or a hiking trail are very low risk, said Linsey Marr, a professor of civil and environmental engineering at Virginia Tech. Viral particles quickly disperse in outdoor air, and the risk of inhaling aerosolized virus from a jogger or passers-by are negligible, she said. Even if a person coughs or sneezes outside as you walk by, the odds of you getting a large enough dose of virus to become infected remain low, she said.“I think the guidelines should be based on science and practicality,” said Dr. Marr. “People only have so much bandwidth to think about precautions. I think we should focus on the areas that have highest risk of transmission, and give people a break when the risk is extremely low.”Dr. Marr uses a simple two-out-of-three rule for deciding when to wear a mask. In every situation, she makes sure she’s meeting two out of three conditions: outdoors, distanced and masked. “If you’re outdoors, you either need to be distanced or masked,” she said. “If you’re not outdoors, you need to be distanced and masked. This is how I’ve been living for the past year. It all comes down to my two-out-of-three rule.”Use the 2-out-of-3 RuleTo lower risk for Covid-19, make sure your activity meets two out of the following three conditions: outdoors, distanced and masked.Outdoors + Distanced = No Mask NeededOutdoors + No Distance = Mask NeededNot Outdoors + Distanced = Mask NeededWhen masks are needed outdoorsIf you stop to have an extended conversation with someone who isn’t vaccinated, masks are recommended. Even outdoors, your risk of breathing someone else’s air increases the longer and closer you stand to them. One of the few documented cases of outdoor transmission happened in China early in the pandemic, when a 27-year-old man stopped to chat outside with a friend who had just returned from Wuhan, where the virus originated. Seven days later, he had his first symptoms of Covid-19.And masks are still advised if you find yourself in an outdoor crowd. Standing shoulder to shoulder with strangers during an outdoor concert or a protest could increase risk, particularly for the unvaccinated.Recently while hiking without a mask, Dr. Marr said she still made an effort to keep her distance from large groups when the trail got crowded.“If I was passing by a solo hiker it didn’t concern me,” said Dr. Marr. “But if I passed by a group of 10 hikers in a row, I stepped further off the path. The risk is still low, but at some point there could be a large enough pack of people that the risk could become appreciable.”When outdoor risk is lowestWalking your dog, riding a bike, hiking on a trail or picnicking with members of your household or vaccinated friends are all activities where the risk for virus exposure is negligible. In these kinds of situations, you can keep a mask on hand in your pocket, in case you find yourself in a crowd or need to go indoors..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-rqynmc{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.9375rem;line-height:1.25rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-rqynmc{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-rqynmc strong{font-weight:600;}.css-rqynmc em{font-style:italic;}.css-yoay6m{margin:0 auto 5px;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}@media (min-width:740px){.css-yoay6m{font-size:1.25rem;line-height:1.4375rem;}}.css-1dg6kl4{margin-top:5px;margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}#masthead-bar-one{display:none;}#masthead-bar-one{display:none;}.css-1pd7fgo{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-1pd7fgo{padding:20px;width:100%;}}.css-1pd7fgo:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1pd7fgo{border:none;padding:20px 0 0;border-top:1px solid #121212;}.css-1pd7fgo[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-1pd7fgo[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-1pd7fgo[data-truncated] .css-5gimkt:after{content:’See more’;}.css-1pd7fgo[data-truncated] .css-6mllg9{opacity:1;}.css-1rh1sk1{margin:0 auto;overflow:hidden;}.css-1rh1sk1 strong{font-weight:700;}.css-1rh1sk1 em{font-style:italic;}.css-1rh1sk1 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#ccd9e3;text-decoration-color:#ccd9e3;}.css-1rh1sk1 a:visited{color:#333;-webkit-text-decoration-color:#ccc;text-decoration-color:#ccc;}.css-1rh1sk1 a:hover{-webkit-text-decoration:none;text-decoration:none;}“I think it’s a bit too much to ask people to put the mask on when they go out for a walk or jogging or cycling,” said Dr. Muge Cevik, a clinical lecturer of infectious disease and medical virology at the University of St. Andrews School of Medicine in Scotland, where outdoor masking has never been required. “We’re in a different stage of the pandemic. I think outdoor masks should not have been mandated at all. It’s not where the infection and transmission occurs.”“Let me go for my run, maskless. Mask in pocket,” tweeted Dr. Nahid Bhadelia, an infectious diseases physician and the medical director of the special pathogens unit at Boston Medical Center. “Given how conservative I have been on my opinions all year, this should tell you how low risk is, in general, for outdoors transmission for contact over short periods — and lower still after vaccination. Keep the masks on you for when you are stationary in a crowd and headed indoors.”To understand just how low the risk of outdoor transmission is, researchers in Italy used mathematical models to calculate the amount of time it would take for a person to become infected outdoors in Milan. They imagined a grim scenario in which 10 percent of the population was infected with Covid-19. Their calculations showed that if a person avoided crowds, it would take, on average, 31.5 days of continuous outdoor exposure to inhale a dose of virus sufficient to transmit infection.“The results are that this risk is negligible in outdoor air if crowds and direct contact among people are avoided,” said Daniele Contini, senior author of the study and an aerosol scientist at the Institute of Atmospheric Sciences and Climate in Lecce, Italy.Even as more-infectious virus variants circulate, the physics of viral transmission outdoors haven’t changed, and the risk of getting infected outdoors is still low, say virus experts. Pay attention to the rates of infection in your community. If case counts are surging, your risk of encountering an infected person goes up.When outdoor fun moves indoorsDr. Cevik notes that debates about outdoor masking and articles showing photos of crowded beaches during the pandemic have left people with the wrong impression that parks and beaches are unsafe, and distracted from the much higher risks of indoor transmission. Often it’s the indoor activities associated with outdoor fun — like traveling unmasked in a subway or car to go hiking, or dropping into a pub after spending time at the beach — that pose the highest risk. “People hold barbecues outdoors, but then they spend time indoors chatting in the kitchen,” said Dr. Cevik.As more people get vaccinated, decisions about going maskless outdoors will get easier. While no vaccine offers 100 percent protection, the rate of breakthrough infections so far has been exceedingly low. The U.S. Centers for Disease Control and Prevention recently reported just 5,800 cases of breakthrough infections among 75 million vaccinated people. And the C.D.C. has said vaccinated friends and family members can safely spend time together, without masks.But it’s OK to keep wearing your mask outdoors if you prefer it. After a year of taking pandemic precautions, it may be hard for people to adjust to less restrictive behaviors. Sarit A. Golub, a psychology professor at Hunter College of the City University of New York, said it’s important for both the media and public health officials to communicate the reasons people can modify some behaviors, like outdoor masking.“In the coming months, ‘normal life’ will begin to become safer, but I worry that some people won’t be willing or able to relax pandemic restrictions in ways that makes sense,” Dr. Golub said. “I worry that folks have internalized the fear messaging without understanding the reasons behind specific behavioral recommendations, and therefore, the reasons that they can be modified as circumstances change.”Gregg Gonsalves, assistant professor of epidemiology at the Yale School of Public Health, said he recently was with a group of parents, including many vaccinated physicians, who met in a New Haven park to celebrate a child’s first birthday. “We’re all just standing around, everybody was masked, and then we started asking, ‘When’s the time we can be outside and take off our masks?’” Dr. Gonsalves said. “If people are vaccinated and you’re outdoors, masks are probably superfluous at this point.”But Dr. Gonsalves said he understands why some people may be reluctant to give up their masks outdoors. “Some of this is Covid hangover,” he said. “We’ve been so traumatized by all of this. I think we need to have a little bit of compassion for the people having trouble letting go.”Illustrations by Eden Weingart