University of Minnesota Medical School researchers have offered new ways to think about the immune system thanks to a recent study published in Nature. Their research, which indicates organ tissues become increasingly immune throughout life, may begin to alter fundamental ideas regarding the rules of vaccination and the immune system’s function within the body.
Saythi Wijeyesinghe, PhD, the lead author on the study is a researcher in the Masopust Lab at the U of M Medical School, which focuses on T cell immunity. His research began with the goal to understand the lifespan of T cells in organ tissues, which are known to fight off viruses while also protecting from reinfection by the same virus.
“Historically, studies of the immune system have emphasized its renewable nature through bone marrow, lymphoid organs and blood. Our work shows how much this model fails to account for the many immune cells distributed throughout other organs of the body, where most infections and tumors arise,” Wijeyesinghe said. “What we found ends up painting a much broader picture of how the immune system accomplishes surveillance of the entire body for pathogens, tissue damage and tumors.”
The study’s major findings, include:- Antiviral T cells that reside in most organs of the body persist over time and in the face of extensive infectious exposures; – Unlike other organ systems, the immune system becomes increasingly immune throughout life, which is a natural response to accumulated microbial exposures over time; – Up to 25% of the cells in organs were immune cells, indicating that the immune system significantly contributes to the cellular makeup of the body; – And, along with antiviral T cells, most other immune cells are durably tissue-resident in organs as well. Wijeyesinghe hopes this study can further advance the ongoing change in how the broader scientific community conceptualizes the immune system and immune homeostasis.During this study, Wijeyesinghe also unexpectedly discovered how tissue-resident T cells may serve as the origin for memory T cells in blood. As a next step in this research, the Masopust Lab is developing new techniques to trace the fate of these immune cells, hoping to further dissect the relationship between blood-borne and tissue-based immunity.
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Materials provided by University of Minnesota Medical School. Original written by Angel Mendez. Note: Content may be edited for style and length.

A recent study suggests that preserving physical and mental health helps older adults experiencing cognitive impairment stave off declines in cognitive engagement.
“We found that declines in physical and mental health were associated with more pronounced cognitive disengagement,” says Shevaun Neupert, corresponding author of the study and a professor of psychology at North Carolina State University. “The impact of declines in physical health was particularly pronounced for study participants who had more advanced cognitive impairment to begin with.”
There’s a lot of research showing that cognitive engagement can help older adults maintain cognitive health. However, the vast majority of that work has been done on healthy adults.
“There’s very little work on cognitive engagement in people who are already cognitively impaired, such as people who have been diagnosed with dementia,” Neupert says. “Are they still capable of sustained cognitive engagement? What factors contribute to that engagement?”
To begin addressing those questions, the researchers enlisted 28 study participants. All of the participants were over 60 and had documented cognitive impairment. Participants came to a testing site two times, six months apart. On each visit, researchers collected data on the physical and mental health of the study participants and performed a battery of tests designed to assess cognitive ability. Participants were also connected to a device that tracked blood pressure continuously and then asked to engage in a series of increasingly difficult cognitive tasks. This allowed researchers to track how cognitive engagement changed as the tasks become progressively harder.
Cognitive engagement means taking part in activities that are mentally challenging. Monitoring blood pressure allows the researchers to track how hard study participants are working to accomplish cognitive tasks. Specifically, blood pressure rises as more blood is pumped to the brain when participants work harder at these tasks.
Broadly speaking, the researchers found that if a participant’s cognitive ability, physical health or mental health declined over the course of the six month study period, that participant became less cognitively engaged as the tasks became harder.
“Normally, you’d expect more engagement as the tasks became harder, but we found that some people essentially stopped trying,” says Claire Growney, co-author of the study and a postdoctoral researcher at Washington University in St. Louis.
“The findings highlight the fact that well-being is holistic; physical health, mental health and cognitive function can influence each other,” says Xianghe Zhu, co-author of the paper and a recent Ph.D. graduate of NC State.
“In practical terms, it suggests that it may be particularly important for people to focus on mental and physical well-being during the early stages of cognitive decline,” Growney says. “Or, at the very least, don’t become so focused on addressing cognitive challenges that you ignore physical health, or create anxiety or emotional distress for yourself that leads to mental health problems.”
“Future research will be needed to determine how beneficial it might be for people to take part in cognitively engaging activities once they’ve started experiencing cognitive decline,” Neupert says. “But we already know that there is an element of ‘use it or lose it’ to cognitive function in healthy adults. And while it’s understandable for people to want to avoid tasks that are difficult or challenging, it’s really important to continue challenging ourselves to take part in difficult cognitive activities.”
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Scientists have produced a comprehensive roadmap of muscle aging in mice that could be used to find treatments that prevent decline in muscle mobility and function, according to a report published today in eLife.
The study reveals which molecules in the muscle are most significantly altered at different life stages, and shows that a molecule called Klotho, when administered to mice in old, but not very old, age, was able to improve muscle strength.
Age-related loss of skeletal muscle mass and function — called sarcopenia — is associated with loss of mobility and increased risk of falls. Yet, although scientists know how sarcopenia affects the appearance and behaviour of muscle tissues, the underlying molecular mechanisms for sarcopenia remain poorly understood. Current treatments for sarcopenia largely involve prescribing physical activity or dietary modifications, and these have shown moderate success.
“Although there are no proven treatments for sarcopenia yet, there are some pharmaceutical treatments entering clinical trials. Interestingly, many of these act on mechanisms that also involve a protein called Klotho,” says co-first author Zachary Clemens, Doctoral Student at the Department of Environmental and Occupational Health, University of Pittsburgh, Pennsylvania, US. “Evidence suggests that Klotho levels gradually decline with age, and so we wanted to test whether supplementation with Klotho may attenuate the development of sarcopenia.”
The team first characterised and compared changes in the structure, function and gene activity in skeletal muscle across the lifespan in mice. They grouped mice into four age categories — young, middle-aged, old and oldest-old — and looked at muscle weight, type of muscle fibers, whether the muscles had accumulated fat, and skeletal muscle function. Although old mice displayed mild sarcopenia, the common clinical features of sarcopenia were only present in the oldest-old mice.
Next, they looked at changes in muscle gene activity and found a progressive disruption in genes known to be associated with the hallmarks of aging from the young to the oldest-old mice.
“To date, most studies in skeletal muscle have focused on the identification of specific pathways that are associated with sarcopenia to identify a molecular mechanism linked to the condition,” explains co-first author Sruthi Sivakumar, Doctoral Student at the Department of Bioengineering, University of Pittsburgh. “We employed an integrative approach, where we created a network by converting gene expression levels to protein-protein interactions, and then we studied how this interaction network changed over time.”
From this network, the team determined the ‘network entropy’ of the muscle cells as a means to estimate the loss of molecular order within the system over time. They found the greatest difference in order between the young and old age groups (at which point it reached maximal entropy), with little difference between the old and oldest-old mice. Additionally, when they looked at human muscle gene data from different age groups, they saw that entropy reached its lowest level in the fourth decade of life, after which time entropy escalated. This was of interest to the team as the fourth decade of life is the time point when sarcopenia often starts to develop.
Next, they looked at whether administering Klotho to mice would have beneficial effects on the muscle healing after injury. They found that applying Klotho after muscle injury reduced scarring and increased structures associated with force production in the animals. Injured mice that received Klotho also had better muscle function — such as muscle twitch and force production — and their whole-body endurance improved two-fold.
Finally, the team looked at whether giving the mice Klotho could reverse age-related declines in muscle quality and function. They found that Klotho administration led to some improvements in the old mice: force production was improved by 17% and endurance when supporting whole body weight was 60% greater compared to mice without treatment. But this was only seen in the old mice, and not in the oldest-old animals. Further investigation showed that Klotho affected genes associated with the hallmarks of aging in all age groups, but that the oldest-old mice showed a dysregulated gene response.
“Our data suggest that treatment with Klotho may be more effective in slowing the progression of sarcopenia at an earlier time point, rather than rescuing advanced age-related disease, by which time the gene responses seem to be more random,” concludes senior author Fabrisia Ambrosio, Associate Professor at the Department of Physical Medicine and Rehabilitation, University of Pittsburgh. “It will be interesting in future studies to determine whether boosting Klotho levels at a younger age could prevent muscle declines into old, and even oldest-old, age.”
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An overgrowth of yeast in the gut within the first few months of life may cause changes to the immune system that increase the risk of asthma later on, shows a study published today in eLife.
Asthma is a common and sometimes difficult-to-manage, life-long lung condition that affects one in 10 children in developed countries. The findings explain a possible cause of asthma and may help scientists develop new strategies to prevent or treat the condition.
The period just after birth is a critical window for the development of a healthy immune system and gut microbiome. Disruptions to gut bacteria that produce anti-inflammatory compounds called short-chain fatty acids (SCFAs) early in life have previously been linked to asthma.
“We recently showed that overgrowth of a type of gut yeast called Pichia kudriavzevii in newborns in Ecuador is associated with an increased risk of asthma,” says first author Rozlyn Boutin, an MD/PhD student in the Department of Microbiology and Immunology at the University of British Columbia, Vancouver, Canada. “In this study, we wanted to see if we could replicate these findings in children from an industrialised setting and identify how fungi of the gut microbiota affect the development of the immune system.”
Boutin and colleagues began with a study of 123 newborns in Canada, who are part of the CHILD Cohort Study. They again found that an overgrowth of Pichia kudriavzevii in the stools of the newborns during the first three months of life was associated with a higher risk of asthma.
To understand how this yeast overgrowth might contribute to asthma later in life, the team applied Pichia kudriavzevii to newborn mice with immature gut microbiota communities. In this mouse model of asthma, the team found that the newborns exposed to the yeast experienced more lung inflammation than those who were unexposed. Applying Pichia kudriavzevii to an adolescent mouse model, however, did not cause this excess inflammation.
“Our findings show that there is a critical window in early life where disruptions in the gut microbiota caused by Pichia kudriavzevii affect the development of the immune system and increase the risk and severity of asthma later in life,” Boutin says.
Previous studies have shown that bacterial SCFAs have beneficial effects on immune development that protect against asthma. In this study, the team also showed that anti-inflammatory SCFAs produced by gut bacteria inhibit the growth of Pichia kudriavzevii.
“Immune responses to gut microbe disruptions early in life have long-term consequences for diseases of the immune system later in life,” concludes senior author Brett Finlay, Professor at the Michael Smith Laboratories and the Departments of Biochemistry and Molecular Biology, and Microbiology and Immunology, University of British Columbia. “Our study adds to our understanding of microbiota-associated asthma and suggests that inhibiting yeast overgrowth with SCFAs in early life could be an effective approach to preventing this condition.”
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SharecloseShare pageCopy linkAbout sharingimage copyrightReutersThe EU’s drugs regulator has said that blood clots should be listed as a “very rare” side effect of the Johnson & Johnson Covid-19 vaccine.The European Medicines Agency said in a statement that it had found a “possible link” between the jab and clots.But it added that the benefits of the Covid-19 vaccine outweighed the risks.Out of more than seven million people who have received the jab in the US, eight people developed rare blood clots, including one person who died.Earlier this month, the EMA made the same recommendation for the Covid-19 vaccine produced by Oxford-AstraZeneca.That recommendation, made on 7 April, came after 86 out of 25 million Europeans administered with the jab developed the unusual blood clots.The UK then stopped administering the AstraZeneca vaccine to people under 30 years old.Last week, the EU, the US and South Africa paused the rollout of the Johnson & Johnson jab in response to the reports of rare blood clotting.What did the EMA say?In a statement released on Tuesday, the EMA recommended that blood clots should be listed as a “very rare” side effect of the Johnson & Johnson vaccine (also known as the Janssen vaccine).The cases of clotting in the US “occurred in people under 60 years of age within three weeks after vaccination, the majority in women”, the regulator said.Covid-19 vaccines: Which ones are availableRare blood clots – what you need to knowIs the Oxford-AstraZeneca vaccine safe?”One plausible explanation for the combination of blood clots and low blood platelets is an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin called heparin induced thrombocytopenia, HIT,” it said.Heparin is a blood thinner given to people with clotting disorders.But the risks associated with the virus itself are still higher than the vaccine, it added.”Covid-19 is associated with a risk of hospitalisation and death,” the EMA said. “The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of [the Johnson & Johnson] Covid-19 vaccine in preventing Covid-19 outweigh the risks of side effects.”These possible side effects seen with the Oxford/AstraZeneca Covid vaccine and now the Janssen/Johnson & Johnson shot are very rare.It doesn’t mean either are no good or unsafe to use in vaccination programmes. Experts say, for most individuals, the benefits of getting immunised clearly outweigh any potential risks. Covid infection can be extremely dangerous and cause harmful blood clots at a much higher frequency than these ultra-unusual events that have been linked to vaccination. Any approved treatment or vaccine will have some side effects and these are listed on or in the pack. The EMA’s safety committee says a warning about rare blood clots should be added to the Janssen vaccine’s product information. Experts are still exploring the link but say it might be related to an unusual immune response in some individuals. What are the symptoms?While the risk of developing a blood clot is extremely low, and the risks associated with Covid-19 itself are still greater, the EMA is warning people to be aware of the symptoms of clots if they’re getting the Johnson & Johnson vaccine.The symptoms to be aware of after getting the vaccine are:Shortness of breathChest painLeg swellingPersistent abdominal painNeurological symptoms, such as severe and persistent headaches or blurred visionTiny blood spots under the skin beyond the site of the injectionIf a person develops any of these symptoms within three weeks of getting the jab, they should seek urgent medical attention.

SharecloseShare pageCopy linkAbout sharingimage copyrightPA MediaIndia’s addition to the UK’s “red list” of banned countries due to rising Covid cases and concerns over a new variant may have come too late, the UK’s former chief scientific adviser has said.Prof Mark Walport told the BBC he believed the new variant was “more transmissible” and there were “good reasons” for keeping it out of the UK.Health officials say it is too early to know whether it is more transmissible.India has been reporting more than 200,000 cases daily since 15 April.Its capital Delhi announced a week-long lockdown after a record spike in cases overwhelmed the city’s healthcare system.From 04:00 BST on Friday 23 April, most people who have travelled from India in the last 10 days will be refused entry to the UK.British or Irish passport holders, or people with UK residence rights, will be allowed in but must quarantine in a government-approved hotel for 10 days.Meanwhile, Prime Minister Boris Johnson is expected to hold a coronavirus press briefing in Downing Street at 17:00 BST.He will joined by the medical director of primary care for NHS England, Dr Nikita Kanani.Why was India not already on the red list?What is the Indian variant?’Avoid 80% of countries’ because of pandemic – USOf the decision to put India on the UK’s red list, Prof Walport told BBC Breakfast: “These decisions are almost inevitably taken a bit too late in truth, but what’s absolutely clear is that this variant is more transmissible in India.”He said he believed it was becoming the “dominant variant” in India, while there were also concerns it could be more effective at escaping a natural or vaccine-induced immune response, “so there’s good reasons for wanting to keep it out of the country if at all possible”.The Indian variant – officially known as B.1.617 – has been designated a “variant under investigation” in the UK, with 103 cases – almost all linked to travel – identified in Britain so far.Prof Sharon Peacock, director of the UK’s genetic surveillance programme, Covid-19 Genomics UK, said the variant had been around for “some time” and was first identified in October last year.She said it was “not clear at the present time” whether it was “the main driver” for the wave of infections in India, but putting the country on the travel red list was necessary due to an “upward trend” in UK cases involving the variant.Viruses change or mutate all the time, so the arrival of this new variant is not surprising. It’s one of many thousands. But how worrying is it?Chat with the experts and they will tell you “watch this space”.Certainly, some of the genetic changes it’s undergone might make it more contagious or able to escape some of the protection given by current vaccines or past Covid-19 infection.More checks and tests are needed to know for sure.Scientists are urgently studying its behaviour and spread to judge the threat.It’s possible it will need to be added to the UK government’s variants of concern list, alongside the variants first seen in South Africa, Brazil and Kent.These variants are on the list because evidence suggests they appear to transmit and infect more easily, may be riskier to health or might compromise vaccination efforts if left to run rampant.There’s no suggestion yet that the Indian variant will outcompete these or become dominant in the UK.More than 100 cases of the Indian variant have been confirmed in the UK. That may sound like a large number, but it is less than 1% of the Covid samples that have been analysed for their genetic make-up in the UK.In the meantime, keeping all cases of Covid down will help prevent illness and deaths while the vaccine rollout continues.Non-essential travel is banned from the UK and those arriving must quarantine. People can currently travel abroad for a limited number of reasons, such as education or work.The earliest date non-essential travel will be allowed from England, Scotland or Wales is 17 May, while Northern Ireland has not set a date.All returning passengers must show proof of a negative Covid test taken within 72 hours before travelling – which can take the form of a printed document, email or text message.On Tuesday, MPs heard that about 100 people are trying to enter England each day with a fake negative Covid certificate.Lucy Moreton, of the Immigration Services Union, which represents UK border and customs staff, told the All Party Parliamentary group on coronavirus that the documents are “very easy” to forge.Asked how many fakes could be slipping through the net, Ms Moreton said it is “inherently unknowable”, adding that a lot of border and quarantine controls are based on “trust”.She told the committee that long queues found at airports could be a “breeding ground” for coronavirus.When can I go on holiday in the UK or abroad?India to start vaccinating all adults over 18’New flights to beat quarantine will cost us up to £6,000’Kirthi Mundhada and her husband Nishant Mehta travelled to Hyderabad, India, for her brother’s wedding and to see her parents, who are unwell.The couple, who live in Brighton, have return flights for 16 May and are now trying to find flights home before 23 April – which is when India is added to the red list.But they say flights will cost between £2,000 and £6,000, which is money they do not have.”It’s so stressful,” Kirthi, 35, says. “I don’t know what’s going to happen with work and we have a mortgage and bills to pay. “Hotel quarantine will cost us around £2,500 and we don’t have much money.”image copyrightVick BusaVick Busa says he and his wife Isha had to travel to India with their two-year-old daughter Aahana for a family emergency.The family, who are from Essex, were due to return to the UK last month, but after India started restricting flights, theirs was cancelled. Vick, who is currently in Ghaziabad in Uttar Pradesh, tried to find flights returning before the new rules kick in, but says the family will now have to quarantine as their flights are not until 4 May.He worries it will be “very difficult” being “locked up in a room for 10 days with stringent rules” with their young daughter.A briefing document drawn up by officials at Public Health England shows that between 25 March and 7 April, 3,345 arrivals from India were registered in UK border travel data. Of those 161 – or 4.8% – tested positive for Covid-19 after a PCR test.The new travel rule applies to England and Scotland. There are currently no direct international flights into Wales or Northern Ireland.The announcement came after Prime Minister Boris Johnson cancelled a planned trip to India, which had been due to take place on 26 April, amid rising cases there.Meanwhile the UK recorded a further 33 deaths within 28 days of a positive coronavirus test and 2,524 new infections, according to the latest government figures.The data also showed that more than 33m people in the UK have had a first dose of a Covid vaccine, while more than 10.4m have received both doses. LOOK-UP TOOL: How many cases in your area?LOCKDOWN RULES: What are they and when will they end?SOCIAL DISTANCING: How can I meet my friend safely? MENTAL HEALTH IN THE PANDEMIC: Stacey Dooley experiences how the pandemic is affecting patientsA HARMLESS ACT TURNED INTO A SEVERE ADDICTION: Gambling turned Tony’s life upside downHow will these new travel restrictions affect you? Get in touch by emailing haveyoursay@bbc.co.uk.Please include a contact number if you are willing to speak to a BBC journalist. You can also get in touch in the following ways:WhatsApp: +44 7756 165803Tweet: @BBC_HaveYourSayPlease read our terms & conditions and privacy policy

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SharecloseShare pageCopy linkAbout sharingimage copyrightReutersThe US state department is to advise Americans to avoid 80% of countries worldwide because of the coronavirus pandemic.In a note to the media about its updated travel guidance, it said the pandemic continued to “pose unprecedented risks to travellers”.The current US “Do Not Travel” advisory covers 34 out of 200 countries.Covid-19 has now claimed more than three million lives worldwide – more than half a million of them in the US. The World Health Organization (WHO) warned the world was “approaching the highest rate of infection” so far, despite the global rollout of vaccination programmes.India – currently in the grip of a second wave – is to begin offering vaccinations to all adults over 18 in a bid to control the surge in infections.Covid map: Where are cases the highest?The US state department said its decision to update its travel advisories was to bring it more in line with those from the Centers for Disease Control and Prevention (CDC) and “does not imply a reassessment of the current health situation in a given country”.However, it said the move would “result in a significant increase in the number of countries at Level 4: Do Not Travel, to approximately 80% of countries worldwide”. Anyone planning to travel to a country in the remaining 20% is advised to reconsider before proceeding.Which countries move to level four?The state department has not revealed which countries will be added to the level four category – the highest of its four risk levels. Guidance will be issued individually for each country in the next few days.Currently, only three places in the world are assessed at the lowest tier – level one, which advises “Exercise normal precautions”. They are Macau, Taiwan and New Zealand. Even Antarctica is at level two – “Exercise increased caution” – while the UK is at level three – “Reconsider travel” – with an extra warning to exercise caution because of the risk of terrorism. The CDC currently recommends all Americans refrain from travelling domestically until they have been fully vaccinated and warns that international travel “poses additional risks” even for those vaccinated. In addition, all air passengers coming to the US, including US citizens, must have a negative Covid test result or documentation of recovery from the virus before they board a flight.Will Covid vaccines work against new variants? How will Covid vaccines be shared around the world?While more than 860 million doses of coronavirus vaccine have been administered in 165 countries worldwide, many countries are still struggling to contain the virus.Brazil has recorded the third-highest number of cases and, at 368,749, the second-highest number of deaths in the world. Canada has also reported a recent rise in cases and Papua New Guinea has been highlighted as a cause for concern. While some countries – such as Israel and the UK – have secured and delivered doses to a large proportion of their population, many more countries are still waiting for their first shipments to arrive.That is leading to warnings about growing “vaccine inequity” – jabs not being being shared fairly between rich and poorer countries.

A novel system of chilled panels that can replace air conditioning can also help reduce the risk of indoor disease transmission, suggests new analysis from the University of British Columbia, University of Pennsylvania and Princeton University.
The researchers computed air conditioning requirements in 60 of the world’s most populous cities — with the additional ventilation required due to COVID-19. Then, they compared the energy costs with their cooling method, using the chilled panels and natural ventilation.
The results, published in the COVID-19 edition of Applied Energy, showed that the alternative solution can save up to 45 per cent of the required energy, while ensuring building occupants are comfortable and rooms are adequately refreshed.
Dr. Adam Rysanek, a professor in the school of architecture and landscape architecture at UBC and co-author of the paper, notes that many public health guidelines, as well as building industry bodies, recommend increasing the flow of fresh, outdoor air into buildings in order to reduce the risk of spreading COVID-19 and other diseases.
“However, if we continue to rely on conventional HVAC systems to increase indoor fresh air rates, we may actually double energy consumption. That’s the nature of conventional HVAC.”
“Alternatively, we can encourage people to install new types of radiant cooling systems, which allow them to keep their windows open even when it’s hot outside. These alternative systems can provide a sufficient level of thermal comfort, increase protection against disease while lessening the impact on the environment,” noted Rysanek, director of the Building Decisions Research Group at UBC’s faculty of applied science.
Rysanek and his colleagues earlier demonstrated their cooling system in the hot and humid climate of Singapore. They built a public pavilion featuring a system of chilled tubes enclosed within a condensation-preventing membrane. This allowed occupants to feel comfortable, and even cold, without changing the air temperature surrounding the human body.
“You can think of it as lean A/C — or, even better, as a green alternative to energy-guzzling air conditioning,” said Rysanek.
Toronto is one of the cities included in the latest analysis, as are Beijing, Miami, Mumbai, New York and Paris. In all these regions, peak summer temperatures can soar past 35 degrees Celsius (95 degrees Fahrenheit).
“A key impact of climate change is the accelerating rise in average and peak temperatures, particularly in urban areas. We are expecting the appetite for indoor cooling will ramp up in the years ahead. Yet, if we want to mitigate urban heat and ensure people are healthy and comfortable while reducing our energy use, we need to seriously consider revolutionising our historical approach to air-conditioning,” adds Rysanek.
Rysanek notes that, though chilled panel systems have been around for decades, adding the special membrane devised by the research team could be the key to making it a commercially viable alternative to traditional HVAC systems in all climates.
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Flushing a toilet can generate large quantities of microbe-containing aerosols depending on the design, water pressure or flushing power of the toilet. A variety of pathogens are usually found in stagnant water as well as in urine, feces and vomit. When dispersed widely through aerosolization, these pathogens can cause Ebola, norovirus that results in violent food poisoning, as well as COVID-19 caused by SARS-CoV-2.
Respiratory droplets are the most prominent source of transmission for COVID-19, however, alternative routes may exist given the discovery of small numbers of viable viruses in urine and stool samples. Public restrooms are especially cause for concern for transmitting COVID-19 because they are relatively confined, experience heavy foot traffic and may not have adequate ventilation.
A team of scientists from Florida Atlantic University’s College of Engineering and Computer Science once again put physics of fluids to the test to investigate droplets generated from flushing a toilet and a urinal in a public restroom under normal ventilation conditions. To measure the droplets, they used a particle counter placed at various heights of the toilet and urinal to capture the size and number of droplets generated upon flushing.
Results of the study, published in the journal Physics of Fluids, demonstrate how public restrooms could serve as hotbeds for airborne disease transmission, especially if they do not have adequate ventilation or if toilets do not have a lid or cover. Most public restrooms in the United States often are not equipped with toilet seat lids and urinals are not covered.
For the study, researchers obtained data from three different scenarios: toilet flushing; covered toilet flushing and urinal flushing. They examined the data to determine the increase in aerosol concentration, the behavior of droplets of different sizes, how high the droplets rose, and the impact of covering the toilet. Ambient aerosol levels were measured before and after conducting the experiments.
“After about three hours of tests involving more than 100 flushes, we found a substantial increase in the measured aerosol levels in the ambient environment with the total number of droplets generated in each flushing test ranging up to the tens of thousands,” said Siddhartha Verma, Ph.D., co-author and an assistant professor in FAU’s Department of Ocean and Mechanical Engineering. “Both the toilet and urinal generated large quantities of droplets smaller than 3 micrometers in size, posing a significant transmission risk if they contain infectious microorganisms. Due to their small size, these droplets can remain suspended for a long time.”
The droplets were detected at heights of up to 5 feet for 20 seconds or longer after initiating the flush. Researchers detected a smaller number of droplets in the air when the toilet was flushed with a closed lid, although not by much, suggesting that aerosolized droplets escaped through small gaps between the cover and the seat.