Publisher Health

With daily reports of breakthrough infections and the rise of the Delta variant, vaccinated people may need to take a few more precautions. Here’s what you need to know.As the Delta variant spreads among the unvaccinated, many fully vaccinated people are also beginning to worry. Is it time to mask up again?While there’s no one-size-fits-all answer to the question, most experts agree that masks remain a wise precaution in certain settings for both the vaccinated and unvaccinated. How often you use a mask will depend on your personal health tolerance and risk, the infection and vaccination rates in your community, and who you’re spending time with.The bottom line is this: While being fully vaccinated protects against serious illness and hospitalization from Covid-19, no vaccine offers 100 percent protection. As long as large numbers of people remain unvaccinated and continue to spread coronavirus, vaccinated people will be exposed to the Delta variant, and a small percentage of them will develop so-called breakthrough infections. Here are answers to common questions about how you can protect yourself and lower your risk for a breakthrough infection.When should a vaccinated person wear a mask?To decide whether a mask is needed, first ask yourself these questions.Are the people I’m with also vaccinated?What’s the case rate and vaccination rate in my community?Will I be in a poorly ventilated indoor space, or outside? Will the increased risk of exposure last for a few minutes or for hours?What’s my personal risk (or the risk for those around me) for complications from Covid-19?Experts agree that if everyone you’re with is vaccinated and symptom-free, you don’t need to wear a mask.“I don’t wear a mask hanging out with other vaccinated people,” said Dr. Ashish K. Jha, dean of the Brown University School of Public Health. “I don’t even think about it. I’m going to the office with a bunch of people, and they’re all vaccinated. I’m not worried about it.”But once you start to venture into enclosed public spaces where the chances of your encountering unvaccinated people is greater, a mask is probably a good idea. Being fully vaccinated remains the strongest protection against Covid-19, but risk is cumulative. The more opportunities you give the virus to challenge the antibodies you’ve built up from your vaccine, the higher your risk of coming into contact with a large enough exposure that the virus will break through the protective barrier provided by your immune system. For that reason, the case rate and vaccination rate of your community is one of the most important factors influencing the need for masks. In Vermont, Massachusetts, Connecticut and Rhode Island, for instance, more than 70 percent of adults are fully vaccinated. In Alabama, Mississippi and Arkansas, fewer than 45 percent of adults are vaccinated. In some counties, overall vaccination rates are far lower.“We’re two Covid nations right now,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Center for Vaccine Development at Texas Children’s Hospital. In Harris County, Texas, where Dr. Hotez lives, case counts are rising, up by 114 percent in the past two weeks, and only 44 percent of the community is fully vaccinated. “I’m wearing a mask indoors most of the time,” said Dr. Hotez.Finally, masking is more important in poorly ventilated indoor spaces than outdoors, where risk of infection is extremely low. Dr. Jah notes that he recently dashed into a coffee shop, unmasked, because vaccination rates are high in his area, and he was only there for a few minutes.Your personal risk matters, too. If you are older or immune compromised, your antibody response to the vaccine may not be as strong as the response in a young person. Avoiding crowded spaces and wearing a mask when you’re indoors and don’t know the vaccination status of those around you is a good idea.Use The Times tracker to find the vaccination rates and case rates in your area.Why is the Delta variant prompting experts to rethink mask guidance?When the U.S. Centers for Disease Control and Prevention announced that vaccinated people could stop wearing masks, case counts were dropping, vaccinations were on the rise and the highly-infectious Delta variant had not yet taken hold. Since then, Delta has spread rapidly and now accounts for more than 83 percent of cases in the United States. People infected with the Delta variant are known to shed much higher levels of virus for longer periods of time compared with earlier lineages of the coronavirus. One preliminary study estimated the viral load is 1,000 times greater in people with the Delta variant. These high viral loads give the virus more opportunities to challenge your antibodies and break through your vaccine’s protection.“This is twice as transmissible as the original lineage of Covid,” said Dr. Hotez. “The reproductive number of the virus is around 6,” he said, referring to the number of people a virus carrier is likely to infect. “That means 85 percent of the population needs to be vaccinated. Only a few areas of the country are reaching that.”Is it safe for vaccinated people to go to restaurants, museums, the movies, a wedding or other large gatherings?The answer depends on your personal risk tolerance and the level of vaccinations and Covid-19 cases in your community. The more time you spend with unvaccinated people in enclosed spaces for long periods of time, the higher your risk of crossing paths with the Delta variant, or any other variants that may crop up. Large gatherings, by definition, offer more opportunities to get infected with coronavirus, even if you’re vaccinated. Scientists have documented breakthrough infections at a recent wedding in Oklahoma and July 4 celebrations in Provincetown, Mass. But even with the Delta variant, full vaccination appears to be about 90 percent effective at preventing serious illness and hospitalization from Covid-19. If you are at very high risk for complications from Covid-19, however, you should consider avoiding risky situations and wearing a mask when the vaccination status of those around you is unknown. Healthy vaccinated people who are at low risk of complications have to decide what level of personal risk they are willing to tolerate. Wearing a mask at larger indoor gatherings will lower their risk for infection. If you’re healthy and vaccinated but caring for an aging parent or spending time with others at high risk, you should consider their risk too when deciding whether to attend an event or wear a mask.“If I go into a public area, I’ll generally wear a mask,” said Dr. Hotez. “Up until recently I took my son and his girlfriend out for dinner in a restaurant, and I wouldn’t wear a mask because transmission was way down. Now I’m not so sure. I may readjust my thinking about restaurants while Delta is accelerating.”If breakthrough infections are rare, why do I keep hearing about them?Breakthrough infections get a lot of attention because vaccinated people talk about them on social media. When clusters of breakthrough infections happen, they also are reported in science journals or the media. But it’s important to remember that while breakthrough cases are relatively rare, they can still occur no matter what vaccine you get. “No vaccines are 100 percent effective at preventing illness in vaccinated people,” the C.D.C. states on its website. “There will be a small percentage of fully vaccinated people who still get sick, are hospitalized or die from Covid-19.” A breakthrough case doesn’t mean your vaccine isn’t working. In fact, most cases of breakthrough infections result in no symptoms or only mild illness, which shows the vaccines are working well to prevent serious illness from Covid-19.As of July 12, more than 159 million people in the United States had been fully vaccinated against Covid-19. Of those, just 5,492 had breakthrough cases that resulted in serious illness, including 1,063 who died. That’s less than 0.0007 percent of the vaccinated population. Meanwhile, 99 percent of deaths from Covid-19 are among the unvaccinated.Many infectious disease experts are frustrated that the C.D.C. is only documenting cases in which a vaccinated person with Covid-19 is hospitalized or dies. But many breakthrough infections still are being detected in asymptomatic people who are being tested frequently, like baseball players and Olympic athletes. Many of those people are traveling or spending extended periods of time in close quarters with others. “Sports figures are different,” said Dr. Jha. “Part of the problem is they are also encountering a lot of unvaccinated people, including in their own little circle.”I’m vaccinated. How often should I be tested for Covid-19?If you’re fully vaccinated and you know you’ve been exposed to someone with Covid-19, it’s a good idea to be tested, even if you don’t have symptoms.And if you have cold symptoms or any other signs of infection, experts agree you should be tested. Many vaccinated people who aren’t wearing masks have picked up summer colds that cause runny noses, fever and coughing. But it’s impossible to tell the difference between a summer cold and Covid-19. Anyone with cough or cold symptoms should wear a mask to protect those around them and get tested to rule out Covid-19. It’s a good idea to keep a few home Covid tests on hand as well.“If I woke up one morning and had cold symptoms, I would put on a mask at home, and I would get myself tested,” said Dr. Jha. “I don’t want to cause breakthrough infections for other members of my family, and I don’t want to give it to my 9-year-old kid.”

Engineers at the University of California San Diego developed a soft and stretchy ultrasound patch that can be worn on the skin to monitor blood flow through major arteries and veins deep inside a person’s body.
Knowing how fast and how much blood flows through a patient’s blood vessels is important because it can help clinicians diagnose various cardiovascular conditions, including blood clots; heart valve problems; poor circulation in the limbs; or blockages in the arteries that could lead to strokes or heart attacks.
The new ultrasound patch developed at UC San Diego can continuously monitor blood flow — as well as blood pressure and heart function — in real time. Wearing such a device could make it easier to identify cardiovascular problems early on.
A team led by Sheng Xu, a professor of nanoengineering at the UC San Diego Jacobs School of Engineering, reported the patch in a paper published July 16 in Nature Biomedical Engineering.
The patch can be worn on the neck or chest. What’s special about the patch is that it can sense and measure cardiovascular signals as deep as 14 centimeters inside the body in a non-invasive manner. And it can do so with high accuracy.
“This type of wearable device can give you a more comprehensive, more accurate picture of what’s going on in deep tissues and critical organs like the heart and the brain, all from the surface of the skin,” said Xu.

For much of human history, animals and plants were perceived to follow a different set of rules than the rest of the universe. In the 18th and 19th centuries, this culminated in a belief that living organisms were infused by a non-physical energy or “life force” that allowed them to perform remarkable transformations that couldn’t be explained by conventional chemistry or physics alone.
Scientists now understand that these transformations are powered by enzymes — protein molecules comprised of chains of amino acids that act to speed up, or catalyze, the conversion of one kind of molecule (substrates) into another (products). In so doing, they enable reactions such as digestion and fermentation — and all of the chemical events that happen in every one of our cells — that, left alone, would happen extraordinarily slowly.
“A chemical reaction that would take longer than the lifetime of the universe to happen on its own can occur in seconds with the aid of enzymes,” said Polly Fordyce, an assistant professor of bioengineering and of genetics at Stanford University.
While much is now known about enzymes, including their structures and the chemical groups they use to facilitate reactions, the details surrounding how their forms connect to their functions, and how they pull off their biochemical wizardry with such extraordinary speed and specificity are still not well understood.
A new technique, developed by Fordyce and her colleagues at Stanford and detailed this week in the journal Science, could help change that. Dubbed HT-MEK — short for High-Throughput Microfluidic Enzyme Kinetics — the technique can compress years of work into just a few weeks by enabling thousands of enzyme experiments to be performed simultaneously. “Limits in our ability to do enough experiments have prevented us from truly dissecting and understanding enzymes,” said study co-leader Dan Herschlag, a professor of biochemistry at Stanford’s School of Medicine.
By allowing scientists to deeply probe beyond the small “active site” of an enzyme where substrate binding occurs, HT-MEK could reveal clues about how even the most distant parts of enzymes work together to achieve their remarkable reactivity.

A new study, led by University of Minnesota Twin Cities engineering researchers, shows that the stiffness of protein fibers in tissues, like collagen, are a key component in controlling the movement of cells. The groundbreaking discovery provides the first proof of a theory from the early 1980s and could have a major impact on fields that study cell movement from regenerative medicine to cancer research.
The research is published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), a peer-reviewed, multidisciplinary, high-impact scientific journal.
Directed cell movement, or what scientists call “cell contact guidance,” refers to a phenomenon when the orientation of cells is influenced by the alignment of fibers within soft tissues. Cells have protrusions, almost like multiple little arms, that move them within the tissue. Cells obviously don’t have eyes to sense where they are going, so understanding the mechanisms for how they align their movement with the fibers is considered by researchers to be a final frontier in controlling cell migration.
“It’s kind of like if someone dropped you in a swimming pool filled with water and thousands of skinny ropes aligned along the length of the pool and told you to swim laps — and then turned off the lights,” said Robert Tranquillo, the senior researcher on the study and a University of Minnesota professor in the Department of Biomedical Engineering and the Department of Chemical Engineering and Materials Science. “You’d reach out your arms and legs to try to move through the water and figure out the right direction using the ropes.”
Cells need to move for many reasons. They must move to the right places in a developing embryo to become the right cell types. In wound healing, skin cells need to enter into blood clots efficiently to convert the wound into a scar. And research shows that when cancer cells migrate away from solid tumors to spread throughout the body, they’re following tracks of a line of fibers. In more recent years, researchers have found that contact guidance is the underlying cellular mechanism by which they can make engineered tissues for regenerative medicine to regrow, repair, or replace damaged or diseased cells, organs, or tissues.
“Even though we use cell contact guidance for many processes in my lab to engineer tissues to mimic heart valves and blood vessels, the signal that induces the cell movement in an aligned fiber network has been unclear to us all of these years,” said Tranquillo, a Distinguished McKnight University Professor.
In this new study aimed at understanding contact guidance and improving tissue engineering, Tranquillo’s team partnered with researchers at the University of California, Irvine and University of California, Los Angeles to test the mechanical resistance (the stiffness of the fibers) in two different directions in gels of aligned fibers to see if that was a major factor in cell movement instead of the porosity of the fibers or the adhesion (stickiness) of the fibers.
“Using a special set of tools previously unavailable to us, we were able to test skin cells that we consider a ‘work horse’ for developing engineered tissues,” Tranquillo said. “What we found is that when we cross-linked the fibers (connecting them at intersections) and increased the difference in the stiffness in the two directions, but kept all the other factors the same, the cells aligned better. This is evidence that a directional difference in mechanical resistance of the fiber network influences cell orientation and movement.”
This is the first time anyone has been able to prove one major aspect of the contact guidance theory first proposed by Graham Dunn at King’s College in London back in 1982, Tranquillo said.
The next steps are to study the porosity and adhesion of the fibers to see if they have an impact on cell movement, as well as to study other cell types.
“This is just the first step to truly understand how cells move,” Tranquillo added. “If we can learn more about how cells move, it could be a game-changer in many scientific fields.”
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The rapid spread of the Alpha variant of COVID-19 resulted from biological changes in the virus and was enhanced by large numbers of infected people ‘exporting’ the variant to multiple parts of the UK, in what the researchers call a ‘super-seeding’ event.
Results of the largest phylogeographic analysis ever conducted, published today in the journal Science, maps the spread of the variant (also known as lineage B.1.1.7) from its origins in Kent and Greater London in November 2020 to all but five counties in Wales, Scotland, Northern Ireland and England by 19 January.
Dr Moritz Kraemer, lead author on the study and Branco Weiss Research Fellow in Oxford’s Department of Zoology, says, “At the beginning of December 2020 the epicentre of COVID-19 transmission in England shifted rapidly from the North West and North East to London and the South East, as the Alpha variant took hold. As people travelled from London and the South East to other areas of the UK they ‘seeded’ new transmission chains of the variant. This continued as a national ‘super-seeding’ event which did not start to slow until early January. Although travel was curbed, after travel restrictions were introduced on 20 December, this was compensated for by the continued exponential growth in Alpha variant cases.”
The rapid spread of the Alpha variant across the UK, led to initial reports that it could be up to 80% more transmissible than the original strain. This study, published today by researchers at universities including Oxford, Northeastern and Edinburgh, shows mobility significantly affected its spread and early growth rates. According to the researchers, this highlights the need for epidemiologists to work closely with virologists and geneticists rapidly to create accurate transmissibility estimates for new variants.
Professor Oliver Pybus, lead researcher of the Oxford Martin Programme on Pandemic Genomics, explains, “Estimates of Alpha’s transmission advantage over previous strains were initially 80%, but declined through time. We found Alpha’s emergence was a combination of virus genetic changes and transient epidemiological factors. An initial wave of Alpha variant export to places in England with low rates of infection, from the massive outbreak in Kent and Greater London, explains why at first it spread so fast.
“The Alpha variant does contain genetic changes which makes it more transmissible. It is likely the Alpha variant was 30% to 40% more transmissible than the initial strain. And the early estimates were higher because we did not know how much its growth was exacerbated by human mobility and by how many contacts different groups of people have. Crucially, as more variants emerge and spread in other countries worldwide, we must be careful to account for these phenomena when evaluating the intrinsic transmissibility of new variants.”
Verity Hill, co-author and researcher from the University of Edinburgh, expands, “The Alpha variant began by spreading mostly within London and the South East, even during the November lockdown in England. Once this was lifted, it spread rapidly across the country, as human movement increased significantly. Our ability to be able to trace the origins of the Alpha back to a point source in the South East of England has important implications for how new variants arise and how they will spread across the UK.”
Dr Samuel V. Scarpino, lead researcher from the Network Science Institute at Northeastern University and External Faculty at the Santa Fe Institute, highlights the importance of integrative pathogen surveillance systems, “Only by integrating high-resolution genomic, case, testing, and aggregated, anonymous mobility data were we able to identify the drivers of Alpha variant emergence and spread in the UK.
“Uncovering the mechanisms of B.1.1.7 emergence allows governments to respond more effectively and advances our scientific understanding of epidemics. The challenge now is to build similar surveillance systems globally. Equitable, ethical data systems will be critical for ending this pandemic and preventing future ones.”
Dr Kraemer concludes, “As new variants emerge we expect they will spread significantly before travel restrictions are put in place, as likely happened with the Delta variant. Given the scale of its current outbreak, it seems probably that the UK is now an important exporter of the Delta variant across Europe and some other parts of the world.
“The UK has decided to ease its restrictions because of our high vaccination rates and a confidence that we have protected the most vulnerable people in society. But that’s not the case in most other countries and the Delta variant could be starting this process again elsewhere, highlighting the urgent need for faster and equitable distribution of vaccines worldwide.”

A computational analysis of COVID-19 tests suggests that, in order to minimize the number of infections in a population, the amount of testing matters more than the sensitivity of the tests that are used. Philip Cherian and Gautam Menon of Ashoka University in Sonipat, India, and Sandeep Krishna of the National Centre for Biological Sciences TIFR, Bangalore, India, present their findings in the open-access journal PLOS Computational Biology.
Different states in India use different mixes of two main tests for COVID-19: a very sensitive reverse-transcriptase polymerase-chain-reaction (RT-PCR) test and a less sensitive rapid antigen test. Traditional thinking holds that an all-RT-PCR approach will ultimately lead to fewer overall infections. While RT-PCR tests are more sensitive than rapid antigen tests, they are more expensive and do not provide results immediately. Therefore, the precise mix of tests needed to optimize outcomes while accounting for cost constraints has been unclear.
Cherian and colleagues used computational models to conduct simulations of how COVID-19 spreads among a population, given different combinations of tests and the economic tradeoffs between them. Accounting for the movement of people between different locations, they calculated the total number of infections that would occur by the end of a pandemic under each scenario.
The analysis suggests that using only rapid antigen tests could achieve similar outcomes, in terms of total infections, as using only RT-PCR tests — as long as the number of people tested is high enough. This suggests that governments in lower and middle-income countries might be able to achieve optimal outcomes by concentrating on ramping up testing using less sensitive tests which provide immediate results, rather than favoring RT-PCR.
The authors also note that governments should continue to explore different mixes of tests that will yield the biggest reduction in the number of cases. Given that the costs of testing are falling, this mix could also be recalibrated regularly to monitor what makes the most economic sense.
“Tests are continually improving, and the tradeoffs are in favor of rapid testing, even if it is less sensitive,” Menon says. “Modeling the effects of using different combinations of tests, keeping in mind their relative costs, can suggest specific policy changes that will have a substantial effect on changing the trajectory of the epidemic.”
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Infection with dengue virus makes mosquitoes more sensitive to warmer temperatures, according to new research led by Penn State researchers. The team also found that infection with the bacterium Wolbachia, which has recently been used to control viral infections in mosquitoes, also increases the thermal sensitivity of the insects. The findings suggest that global warming could limit the spread of dengue fever but could also limit the effectiveness of Wolbachia as a biological control agent.
“Dengue fever, a potentially lethal disease for which no treatment exists, is caused by a virus, spread by the bite of the mosquito Aedes aegypti. This mosquito is also responsible for transmitting a number of disease-causing viruses, including Zika, chikungunya and yellow fever,” said Elizabeth McGraw, professor and head of the Department of Biology, Penn State. “Aided by increasing urbanization and climate change, this mosquito’s range is expected to overlap with 50% of the world’s population by 2050, dramatically increasing the number of people who could potentially be exposed to these viruses.”
In recent years, research groups around the world have attempted to control these viruses by infecting Ae. aegypti with the bacterium Wolbachia pipientis and then releasing the mosquitoes into the environment, McGraw explained.
“Wolbachia have been shown to prevent viruses, including dengue, from replicating inside mosquitoes,” she said. “Importantly, Wolbachia are passed down to the mosquitoes’ offspring, making them a self-propagating and lower-maintenance approach to disease control in the field.”
McGraw noted that both dengue virus and Wolbachia infect a variety of tissues throughout a mosquito’s body, and although they are not toxic, they do evoke an immune stress response.
“Since mosquitoes that are infected with dengue virus and/or Wolbachia are already suffering a stress response, we thought that they would be less well equipped to deal with an additional stressor, such as heat,” she said.

A new method that analyzes how individual immune cells react to the bacteria that cause tuberculosis could pave the way for new vaccine strategies against this deadly disease, and provide insights into fighting other infectious diseases around the world.
The cutting-edge technologies were developed in the lab of Dr. David Russell, the William Kaplan Professor of Infection Biology in the Department of Microbiology and Immunology in the College of Veterinary Medicine, and detailed in new research published in the Journal of Experimental Medicine on July 22.
For years, Russell’s lab has sought to unravel how Mycobacterium tuberculosis (Mtb), the bacteria that cause tuberculosis, infect and persist in their host cells, which are typically immune cells called macrophages.
The lab’s latest innovation combines two analytical tools that each target a different side of the pathogen-host relationship: “reporter” Mtb bacteria that glow different colors depending on how stressed they are in their environment; and single-cell RNA sequencing (scRNA-seq), which yields RNA transcripts of individual host macrophage cells.
“For the first time ever, Dr. Davide Pisu in my lab combined these two approaches to analyze Mtb-infected immune cells from an in vivo infection,” Russell said.
After infecting mice with the fluorescent reporter Mtb bacteria, Russell’s team was able to gather and flow-sort individual Mtb-infected macrophages from the mouse lung. The researchers then determined which macrophages promoted Mtb growth (sporting happy, red-glowing bacteria) or contained stressed Mtb unlikely to grow (unhappy, green-glowing bacteria).

Researchers who want bacteria to feel right at home in the laboratory have put out a new welcome mat.
Rice University bioengineers and Baylor College of Medicine scientists looking for a better way to mimic intestinal infections that cause diarrhea and other diseases have built and tested a set of hydrogel-based platforms to see if they could make both transplanted cells and bacteria comfy.
As a mechanical model of intestinal environments, the lab’s soft, medium and hard polyethylene glycol (PEG) hydrogels were far more welcoming to the cells that normally line the gut than the glass and plastic usually used by laboratories. These cells can then host bacteria like Escherichia coli that are sometimes pathogenic. The ability to study their dynamics under realistic conditions can help scientists find treatments for the maladies they cause.
The researchers found strong correlation between the stiffness of hydrogels, which mimic intestinal mucus, and how well a diarrhea-causing strain of E. coli adhered to and aggregated atop the epithelial cells that normally line the intestines. They reported that softer hydrogels promoted “significantly greater bacterial adhesion,” which they attribute to mucus and other extracellular matrix components expressed by the cells.
The study led by bioengineer Jane Grande-Allen of Rice’s Brown School of Engineering and Anthony Maresso at Baylor, which appears in Acta Biomaterialia, proved the gels’ value in experiments involving the soft interface between organs and microbial or bacterial pathogens.
The Estes lab at Baylor built its model cultures using enteroids, constructs of intestinal cell cultures that scientists use to understand how epithelial cells respond to infectious invaders. Enteroids can incorporate a variety of cells found in the gut, but before Rice’s hydrogels, they were grown on platforms that did not easily mimic the squishy tissues in host bodies.

It’s a favourite first-order for the day, but while a quick coffee may perk us up, new research from the University of South Australia shows that too much could be dragging us down, especially when it comes to brain health.
In the largest study of its kind, researchers have found that high coffee consumption is associated with smaller total brain volumes and an increased risk of dementia.
Conducted at UniSA’s Australian Centre for Precision Health at SAHMRI and a team of international researchers*, the study assessed the effects of coffee on the brain among 17,702 UK Biobank participants (aged 37-73), finding that those who drank more than six cups of coffee a day had a 53 per cent increased risk of dementia.
Lead researcher and UniSA PhD candidate, Kitty Pham, says the research delivers important insights for public health.
“Coffee is among the most popular drinks in the world. Yet with global consumption being more than nine billion kilograms a year, it’s critical that we understand any potential health implications,” Pham says.
“This is the most extensive investigation into the connections between coffee, brain volume measurements, the risks of dementia, and the risks of stroke — it’s also the largest study to consider volumetric brain imaging data and a wide range of confounding factors.