Study Reveals Connection Between Gut Bacteria and Vitamin D Levels – UC San Diego Health

Last Updated on November 30, 2020 by

Our gut microbiomes — the many bacteria, viruses and other microbes living in our digestive tracts — play important roles in our health and risk for disease in ways that are only beginning to be recognized.

University of California San Diego researchers and collaborators recently demonstrated in older men that the makeup of a person’s gut microbiome is linked to their levels of active vitamin D, a hormone important for bone health and immunity.

The study, published November 26, 2020 in Nature Communications, also revealed a new understanding of vitamin D and how it’s typically measured.

Vitamin D can take several different forms, but standard blood tests detect only one, an inactive precursor that can be stored by the body. To use vitamin D, the body must metabolize the precursor into an active form. 

“We were surprised to find that microbiome diversity — the variety of bacteria types in a person’s gut — was closely associated with active vitamin D, but not the precursor form,” said senior author Deborah Kado, MD, director of the Osteoporosis Clinic at UC San Diego Health. “Greater gut microbiome diversity is thought to be associated with better health in general.”

Kado led the study for the National Institute on Aging-funded Osteoporotic Fractures in Men (MrOS) Study Research Group, a large, multi-site effort that started in 2000. She teamed up with Rob Knight, PhD, professor and director of the Center for Microbiome Innovation at UC San Diego, and co-first authors Robert L. Thomas, MD, PhD, fellow in the Division of Endocrinology at UC San Diego School of Medicine, and Serene Lingjing Jiang, graduate student in the Biostatistics Program at Herbert Wertheim School of Public Health and Human Longevity Sciences. 

Multiple studies have suggested that people with low vitamin D levels are at higher risk for cancer, heart disease, worse COVID-19 infections and other diseases. Yet the largest randomized clinical trial to date, with more than 25,000 adults, concluded that taking vitamin D supplements has no effect on health outcomes, including heart disease, cancer or even bone health. 

“Our study suggests that might be because these studies measured only the precursor form of vitamin D, rather than active hormone,” said Kado, who is also professor at UC San Diego School of Medicine and Herbert Wertheim School of Public Health. “Measures of vitamin D formation and breakdown may be better indicators of underlying health issues, and who might best respond to vitamin D supplementation.” 

The team analyzed stool and blood samples contributed by 567 men participating in MrOS. The participants live in six cities around the United States, their mean age was 84 and most reported being in good or excellent health. The researchers used a technique called 16s rRNA sequencing to identify and quantify the types of bacteria in each stool sample based on unique genetic identifiers. They used a method known as LC-MSMS to quantify vitamin D metabolites (the precursor, active hormone and the breakdown product) in each participant’s blood serum. 

In addition to discovering a link between active vitamin D and overall microbiome diversity, the researchers also noted that 12 particular types of bacteria appeared more often in the gut microbiomes of men with lots of active vitamin D. Most of those 12 bacteria produce butyrate, a beneficial fatty acid that helps maintain gut lining health.

“Gut microbiomes are really complex and vary a lot from person to person,” Jiang said. “When we do find associations, they aren’t usually as distinct as we found here.”

Because they live in different regions of the U.S., the men in the study are exposed to differing amounts of sunlight, a source of vitamin D. As expected, men who lived in San Diego, California got the most sun, and they also had the most precursor form of vitamin D.

But the team unexpectedly found no correlations between where men lived and their levels of active vitamin D hormone. 

“It seems like it doesn’t matter how much vitamin D you get through sunlight or supplementation, nor how much your body can store,” Kado said. “It matters how well your body is able to metabolize that into active vitamin D, and maybe that’s what clinical trials need to measure in order to get a more accurate picture of the vitamin’s role in health.”

“We often find in medicine that more is not necessarily better,” Thomas added. “So in this case, maybe it’s not how much vitamin D you supplement with, but how you encourage your body to use it.”

Kado pointed out that the study relied on a single snapshot in time of the microbes and vitamin D found in participants’ blood and stool, and those factors can fluctuate over time depending on a person’s environment, diet, sleep habits, medications and more. According to the team, more studies are needed to better understand the part bacteria play in vitamin D metabolism, and to determine whether intervening at the microbiome level could be used to augment current treatments to improve bone and possibly other health outcomes.

Additional co-authors of the study include: John S. Adams, UCLA; Zhenjiang Zech Xu, Nanchang University; Jian Shen, Gail Ackermann, UC San Diego; Stefan Janssen, Justus-Liebig-University Gießen; Dirk Vanderschueren, KU Leuven and University Hospitals Leuven; Steven Pauwels, University Hospitals Leuven, KU Leuven, Jessa Hospital; and Eric S. Orwoll, Oregon Health & Sciences University.

Funding for this research came, in part, from the National Institutes of Health (U01AG027810, U01AG042124, U01AG042139, U01AG042140, U01AG042143, U01AG042145, U01AG042168, U01 AR066160 and UL1TR000128).


Just six African nations are home to half the worlds malaria deaths – Africa Times

Last Updated on November 30, 2020 by

Roughly half of the world’s malaria deaths occurred in just six African nations in 2019, while the progress achieved in reducing malaria cases in the last two decades has slowed.

That’s according to the annual World Malaria Report released Monday by the World Health Organization. The six nations – Nigeria, Democratic Republic of Congo, Tanzania, Niger, Mozambique and Burkina Faso – accounted for 51 percent of fatalities, while nations in WHO’s sub-Saharan African region recorded 94 percent of the total overall. The six are among 11 African nations in the “high burden, high impact” initiative launched in 2018.

A slight rise in cases is attributed in part to Africa’s growing population, WHO said, but it also reflects a plateau reached by those high-burden nations. Since 2000, the region has reduced its malaria death toll by 44 percent but there are gaps in access and resources, with the malaria challenge made worse by the COVID-19 pandemic.

In 2019, the US$3 billion in funding fell short of a global goal of $5.6 billion. That shortfall is coupled with disruptions in malaria treatment because of the pandemic, though Algeria remained a bright spot after achieving its official malaria eradication status last year.

“It is time for leaders across Africa – and the world – to rise once again to the challenge of malaria, just as they did when they laid the foundation for the progress made since the beginning of this century,” said WHO Director General Dr. Tedros Adhanom Ghebreyesus. “Through joint action, and a commitment to leaving no one behind, we can achieve our shared vision of a world free of malaria.”

Image: WHO

Scientists develop new tools to detect very early changes in Alzheimer’s disease – News-Medical.Net

Last Updated on November 30, 2020 by

Researchers at the University of Gothenburg in Sweden, together with their colleagues at the Barcelona Beta Research Centre in Spain, the University Medical Centre in Ljubljana, Slovenia, and the University of Paris, have found new forms of tau protein that become abnormal in the very early stages of Alzheimer’s disease before cognitive problems develop. The scientists developed new tools to detect these subtle changes and confirmed their results in human samples.

At a time when the incidence and social costs of dementia and Alzheimer’s disease in particular continue to rise, this breakthrough is very timely as it could enable the detection of the disease much earlier than current approaches. The findings are also important for the testing of therapies against this devastating disease.

Alzheimer’s disease is characterized by two pathological changes in brain tissue. One is a protein called tau while the other involves the amyloid beta peptide. Both can form clumps of aggregates that progressively accumulate in specific areas of the brain. For tau, individual units of the protein can aggregate into finely-ordered fibrillar structures facilitated by a biochemical process called phosphorylation. Throughout the disease process, amyloid beta and phosphorylated tau (p-tau) are released from the brain into cerebrospinal fluid; the amount of the released proteins are used as reliable surrogate markers for clinical diagnoses of Alzheimer’s disease.

Normally, amyloid beta levels in cerebrospinal fluid become abnormal several years before p-tau. The current clinical tests for p-tau become abnormal when memory failings develop. This makes it difficult to identify people with the disease at the very early stages before it is too late. How can we, therefore, reliably detect these sub-threshold disease changes?

Precede clinical signs by several years

To address these challenges, the scientists discovered that there are specific forms of p-tau that undergo very minute increases in cerebrospinal fluid and blood in people with emerging Alzheimer pathology. Consequently, the researchers developed highly sensitive techniques to measure these biological markers that precede clinical signs by several years.

In the first study, conducted in the Alfa parent cohort study at the Barcelona Beta Research Centre (BBRC), with the support of “la Caixa” Foundation, about a third of the 381 people evaluated had brain evidence of Alzheimer pathology but without any cognitive problems, meaning that these changes could not be detected in the clinic by memory assessments. Remarkably, the new p-tau markers correctly identified these emerging abnormalities measured in cerebrospinal fluid and regular blood samples.

Subsequent studies performed in Gothenburg, Paris and Ljubljana revealed that these new markers continue to increase from the preclinical stage through the onset of cognitive problems to the late dementia stages. For this reason, progressive increases in p-tau could provide insights into the biological and clinical development of Alzheimer’s disease. The studies are now published in the leading journals EMBO Molecular Medicine and Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

May change clinical practice

A possible way to improve the chances of future therapies is to test them on people in the very early stages of the disease with elusive biological changes but lacking clinical symptoms including memory failings. Candidate drug trials have not been too successful. The practical challenge, however, is that these very tiny initial changes are incredibly difficult to measure reliably. This compromises our chances to identify and recruit preclinical AD patients for clinical trials.”

Kaj Blennow, Professor of Neurochemistry, University of Gothenburg

Dr. Thomas Karikari, an assistant professor at the University of Gothenburg, who co-led the discovery commented: “The remarkable findings reported in these publications show that the new highly sensitive tools capture the earliest Alzheimer disease changes in the brain in clinically normal people. These tools therefore have the potential to advance population screening and clinical trials.”

According to Dr. Marc Suárez-Calvet, neurologist and ERC researcher at BBRC, “the biomarker detected in blood may change clinical practice in the coming years, since it will improve the diagnosis of patients with Alzheimer’s disease, both in its asymptomatic and symptomatic phases”.

Source:

Journal references:

  • Karikari, T.K., et al. (2020) Head‐to‐head comparison of clinical performance of CSF phospho‐tau T181 and T217 biomarkers for Alzheimer’s disease diagnosis. Alzheimer’s & Dementia. doi.org/10.1002/alz.12236.
  • Suárez‐Calvet, M., et al. (2020) Novel tau biomarkers phosphorylated at T181, T217 or T231 rise in the initial stages of the preclinical Alzheimer’s continuum when only subtle changes in Aβ pathology are detected. EMBO Molecular Medicine. doi.org/10.15252/emmm.202012921.

Does a Vegan Diet Prevent the Coronavirus? Heres What Doctors Think – Green Matters

Last Updated on November 30, 2020 by

Although a plentiful plant-based diet can help reduce the side effects of the coronavirus, it doesn’t completely prevent one from contracting it at all. COVID-19 is contracted through the eyes, nose, and mouth, which means those who follow a vegan diet are just as likely to contract the virus as non-vegans, according to Vegan Friendly. Our point? Vegans have to wear masks and social distance, too!

Also, not all vegan diets can necessarily be deemed “healthy” ones. Following a plant-based diet is only “healthy” if it’s well-balanced with fruits, vegetables, proteins, and complex carbohydrates. Being too restrictive, or consuming unusually high amounts of any one food group can make following a plant-based diet virtually useless, healthwise. If you are just starting out in the world of plant-based foods and need a helping hand, check out our guide on transitioning to a vegan diet for tips.

Getting started in the realm of veganism isn’t always easy, but making a gradual transition is certainly worth your while – not only for the sake of the environment, but also to lower your chances of developing weight problems, diabetes, or heart disease, and ultimately, to mitigate the risk of suffering from the effects of COVID-19. 

Marinomed announces trial of Carragelose in COVID-19 at Swansea University Medical School – EurekAlert

Last Updated on November 30, 2020 by

Vienna, Austria, Swansea UK, November 30, 2020 – Marinomed Biotech AG (VSE:MARI), a globally operating biopharmaceutical company, is pleased to announce today that the Swansea University Medical School plans a clinical trial with Iota-/kappa-carrageenan nasal spray as a COVID-19 Prophylaxis for Healthcare Professionals (ICE-COVID).

The investigator-initiated trial at Swansea will be recruiting 480 healthcare professionals managing COVID-19 patients during the pandemic. Objective of the study is to assess the efficacy of Carragelose nasal and throat spray in reducing the rate, severity, and duration of COVID-19 infections. Further endpoints include infection with other respiratory viruses, usability of the spray for prophylaxis and the effects on quality adjusted life years (QALYs). The ongoing clinical trial is supported by Marinomed Biotech AG, the originator and licensor of Carragelose and Boots UK; the Carragelose nasal spray used in the study is marketed as Boots Dual Defence in the United Kingdom.

The design of the double-blind trial is finalized and planned to start shortly. The study population will be equally randomized into a treatment group (0.12 mg/ml iota-carrageenan / 0.4 mg/ml kappa-carrageenan in 0.5% saline) and a placebo group (0.5% saline) and will apply this study regime three times a day, one dose into each nostril and three throat sprays, over the course of eight weeks .

“With the world in the devastating grip of this SARS-CoV2 pandemic and nurses and doctors especially exposed, we are looking forward this very important clinical data from the Swansea trial. Our pivotal clinical data for Carragelose demonstrated alleviation of different coronavirus infections. Marinomed has been able to show neutralizing activity towards the new coronavirus in vitro earlier this year.” said Dr. Eva Prieschl-Grassauer, Chief Scientific Officer at Marinomed. Adding, “We have very good reason to expect and hope that the trial will confirm our in vitro findings and contribute to validating Carragelose nasal spray as a COVID-19 prophylaxis for the vulnerable community of healthcare professionals, protecting them from contracting COVID-19 infections.”

“After seeing the effects of this pandemic on colleagues caring for patients with COVID-19, we wanted to find a way for research to help protect frontline NHS staff,” said Dr. Zita Jessop, Principal Investigator for the clinical trial and clinician scientist at Swansea University. “Previous studies highlighted the effectiveness of iota-carrageenan-based nasal sprays against coronaviruses, indicating promise against SARS-CoV-2. If the results of this randomised placebo-controlled clinical trial are positive as we expect, this has the potential to add an extra prevention strategy in the fight against COVID-19,” she added.

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About Carragelose®:

Carragelose® is a sulfated polymer from red seaweed and a unique, broadly active anti-viral compound. It is known as a gentle yet effective and safe prevention and treatment against respiratory infections. Several clinical and preclinical studies have shown that Carragelose® forms a layer on the mucosa wrapping entering viruses, thereby inactivating them, and preventing them from infecting cells. Marinomed is holder of the IP rights and has licensed Carragelose® for marketing in Europe, parts of Asia, Canada, and Australia. For a full list of Marinomed’s portfolio of Carragelose® containing nasal sprays, please visit https://www.carragelose.com/en/portfolio/launched-products, for a list of scientific publications on Carragelose®, https://www.marinomed.com/en/publications/scientific-publications.

About Marinomed Biotech AG

Marinomed Biotech AG (Vienna, Austria) is a biopharmaceutical company listed on the Prime Market of the Vienna Stock Exchange. The company focuses on the development of innovative products based on patent-protected technology platforms. The Marinosolv® technology platform increases the efficacy of hardly soluble compounds for the treatment of sensitive tissues such as eyes, nose, lung or gastrointestinal tract. The Carragelose® platform comprises innovative patent-protected products targeting viral infections of the respiratory tract and can reduce the risk of an infection with SARS-CoV-2. Carragelose® is used in nasal sprays, throat sprays and lozenges, which are sold via international partners in over 40 countries worldwide. Further information is available at https://www.marinomed.com/en/technologies-markets/markets.

For further inquiries contact:

Dr. Eva Prieschl-Grassauer

Chief Scientific Officer, Marinomed

Hovengasse 25, 2100 Korneuburg, Austria

T +43 2262 90300

E-mail: eva.prieschl@marinomed.com

http://www.marinomed.com

International Media Contact

MC Services AG

Dr. Brigitte Keller, Julia Hofmann

T +49 89 210228 0

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M: +44 7867 515 918

E-mail: marinomed@mc-services.eu

Media Contact Austria:

Metrum Communications GmbH

Roland Mayrl

T +43 1 5046987-331

E-Mail: r.mayrl@metrum.at

Disclaimer

This press release contains forward-looking statements, which are based on current views, expectations and projections of the management of Marinomed Biotech AG about future events. These forward-looking statements are subject to risks, uncertainties and assumptions that could cause actual results, performance or events to differ materially from those described in, or expressed or implied by, such statements. The current views, expectations and projections of the management of Marinomed Biotech AG may be identified by the context of such statements or words such as “anticipate,” “believe”, “estimate”, “expect”, “intend”, “plan”, “project” and “target”. Forward-looking statements are only valid as of the date they are made and Marinomed Biotech AG does not assume any obligation to update, review or revise any forward-looking statements contained in this press release whether as a result of new information, future developments or otherwise.

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UK records another 12,330 coronavirus cases with 205 deaths – Xinhua | English.news.cn – Xinhua

Last Updated on November 30, 2020 by

LONDON, Nov. 30 (Xinhua) — Another 12,330 people in Britain have tested positive for COVID-19, bringing the total number of coronavirus cases in the country to 1,629,657, according to official figures released Monday.

The coronavirus-related deaths in Britain rose by 205 to 58,448, the data showed.

The figures came as British Environment Secretary George Eustice warned Monday that it may be as late as “next summer” until “we can all start to get back to normal”, depending on a vaccine.

Meanwhile, Eustice said it is “too early to say” if another national lockdown will be needed after Christmas.

“You can’t rule anything out,” Eustice told Sky News.

British Prime Minister Boris Johnson said Sunday that the newly announced coronavirus tiers system has “a sunset” clause, or expiry date, of Feb. 3, after increasing pressure from Tory MPs.

In a letter to colleagues ahead of a vote in the House of Commons (lower house of parliament) on the new measures on Tuesday, Johnson said the tiered system will be reviewed every fortnight.

England is currently under a month-long national lockdown, the second of its kind since the coronavirus outbreak in Britain, in a bid to quell the resurgence of coronavirus.

Johnson has announced a “tougher” tiered system of coronavirus restrictions to replace England’s current lockdown when it ends on Dec. 2.

To bring life back to normal, countries such as Britain, China, Germany, Russia and the United States are racing against time to develop coronavirus vaccines. Enditem

Dapivirine vaginal ring receives WHO prequalification for HIV prevention – Healio

Last Updated on November 30, 2020 by

November 30, 2020

1 min read

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The dapivirine vaginal ring has been prequalified by WHO, bringing the HIV preventive closer to public introduction and approval by individual countries.

The prequalification designation signifies WHO’s stamp of approval that the device meets global standards for quality, safety and efficacy in reducing women’s risk for HIV infection.

According to a press release from the nonprofit International Partnership for Microbicides (IPM), which developed the dapivirine ring and is the product’s regulatory sponsor, women bear a disproportionate burden of the HIV/AIDS epidemic, with nearly 60% of new adult cases in sub-Saharan Africa occurring among women.

The monthly dapivirine ring was previously reported to reduce HIV risk by 39% in the HOPE trial.
Zeda F. Rosenberg, ScD, founder and chief executive officer of the IPM, said in a press release. “Our aim is to make the ring available first in sub-Saharan Africa, where women face persistently high HIV risk.”
According to the press release, the IPM received the rights to develop dapivirine as a vaginal microbicide from Johnson & Johnson, which is partnering with the group to plan the ring’s introduction.

The IPM says it will initially seek approvals for the ring’s use in eastern and southern Africa where “the need is urgent,” and will also submit an application to the FDA in 2020.

WHO urges countries to look very, very carefully at ski season plans – Reuters UK

Last Updated on November 30, 2020 by

A closed chairlift is seen at the ski resort of Passo Tonale in the Dolomites which has become a virtual ghost town after the government decision to close everything down in fear of the rising numbers of coronavirus (COVID-19) infections, in Passo del Tonale, Italy, November 26, 2020. REUTERS/Guglielmo Mangiapane

GENEVA (Reuters) – The World Health Organisation urged countries on Monday to consider carefully any plans for the coming ski season to manage the risks associated with people converging on small areas where the new coronavirus could be spread.

But the global health agency declined to offer a specific recommendation to governments wrestling with the question of whether to allow snow sports this winter.

“We would ask that all countries look at the ski season and other reasons for mass gatherings and look very, very carefully at the associated risks,” said Mike Ryan, the WHO’s top emergency expert.

Reporting by John Miller and Emma Farge; Writing by Hugh Lawson; Editing by Andrew Heavens

Eating foods that promote inflammation may worsen heart failure – SFGate

Last Updated on November 30, 2020 by

People with heart failure who eat a diet high in foods that cause inflammation are twice as likely to end up in the hospital or die as those who eat foods known to reduce inflammation, new research shows.

“If people with heart failure can reduce the amount of pro-inflammatory foods that they eat, it might help with their survival,” said lead researcher JungHee Kang, a nursing research assistant and PhD student at the University of Kentucky in Lexington.

Diet has been shown to play a role in regulating inflammation, which is associated with many chronic illnesses, including heart disease. Diets high in foods such as red meat, refined grains and high-fat dairy products have been shown to increase inflammation, while foods such as olive oil, whole grains, and fruits and vegetables have been shown to lower it.

Kang looked at data from a previous study in which her team asked 213 heart failure patients to keep diaries of what they ate for four days. They then categorized the diets using an index that scores foods based on whether they increase or decrease inflammation. After following participants for a year, they found those whose diets had higher inflammatory scores were more than twice as likely to die or be hospitalized compared to those whose diets had lower inflammatory scores.

The results were presented at the American Heart Association’s virtual Scientific Sessions earlier this month. The research is considered preliminary until published in a peer-reviewed journal.

“It’s well known that diet plays a critically important role in the development of heart disease and stroke,” said Dr. Amit Khera, professor of medicine and director of the preventive cardiology program at the University of Texas Southwestern Medical Center in Dallas. “This is a reminder that diet is important. The only surprise to me was the magnitude of the effect.”

Khera said the study also was important because it looked specifically at heart failure outcomes, whereas previous diet studies focused more on heart attacks and strokes. According to AHA statistics, an estimated 6.2 million U.S. adults have heart failure, which occurs when the heart doesn’t pump enough blood and oxygen to support the other organs in the body.

Many diets that are considered heart-healthy “have more in common than they do differences,” said Khera, an author of AHA and American College of Cardiology guidelines for preventing cardiovascular disease.

For example, the Mediterranean diet, which describes an eating pattern common in countries bordering the Mediterranean Sea, includes olive oil as a primary fat source, a lot of fruits, vegetables, grains, beans, nuts and seeds and low amounts of dairy products, eggs, fish and poultry. The DASH (Dietary Approaches to Stop Hypertension) diet, meanwhile, was designed to help lower blood pressure. It also includes a lot of vegetables, fruits and whole grains and limits foods high in saturated fats. But the DASH diet allows more protein from low-fat dairy, meat and poultry.

The guidelines recommend plant-based and Mediterranean eating patterns, while limiting processed meats, refined carbohydrates, cholesterol, sodium and sweetened drinks.

“There’s a lot of overlap,” Khera said. “It’s like a Venn diagram. The sweet spot is in the middle.”

What’s needed now, Kang said, is research to confirm whether anti-inflammatory diets can be used to reduce heart failure mortality.

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Wuhan mass screening identifies hundreds of asymptomatic cases – EurekAlert

Last Updated on November 30, 2020 by

A mass screening programme of more than 10 million Wuhan residents identified 300 asymptomatic cases, but none were infectious – according to a study involving the University of East Anglia.

The mass testing project took place over two weeks at the end of May – after the city’s stringent lockdown was lifted in April.

The study found no ‘viable’ virus in the asymptomatic cases and the close contacts of these positive asymptomatic cases did not test positive.

But the research team warn that their findings do not show that the virus can’t be passed on by asymptomatic carriers.

Rather, strict non-pharmaceutical interventions such as mask-wearing, hand washing, social distancing and lockdown have helped reduce the virulence of Covid-19.

The study, published in Nature Communications, was led by researchers at the Huazhong University of Science and Technology (HUST) in Wuhan, China – in collaboration with researchers at UEA’s Norwich Medical School.

Prof Fujian Song, from UEA’s Norwich Medical School, said: “Wuhan was the most seriously affected city in China by the Covid-19 pandemic.

“After stringent non-pharmaceutical interventions and lockdown measures from 23 January 2020, the city’s lockdown was lifted on 8 April 2020.

“To assess the post-lockdown risk of Covid-19 in the city, a mass screening project of nearly 10 million Wuhan residents was carried out between May 14 and June 1.

“This screening programme identified 300 asymptomatic cases. But the virus cultures indicated no viable virus in the identified asymptomatic cases. This means that these people were not likely to infect anyone else.”

The asymptomatic cases were found among people aged between 10 and 89, however the asymptomatic positive rate was the lowest in children and teens aged under 17 and highest among people aged over 60.

Further swab testing of 1174 close contacts of these 300 asymptomatic positive cases were all negative.

Prof Song said: “What this tells us is that the infection prevalence of Covid-19 was very low five to eight weeks after the end of lockdown in Wuhan.

“This work confirms that transmission of Covid-19 can be successfully controlled by well implemented non-pharmaceutical interventions, including face covering, hand hygiene, safe social distancing, contract tracing, and lockdown restrictions. Actually, mask wearing remains common in public places now in Wuhan.”

However, the research team say that it is important to emphasise that the results of this study should be correctly interpreted.

Prof Song said: “The asymptomatic cases identified in the screening programme in Wuhan were truly asymptomatic, as none of them showed clinical symptoms before or during their follow-up isolation.

“But there is plenty of evidence elsewhere showing that people infected with Covid-19 may be temporarily asymptomatic and infectious before going on to develop symptoms.

“It’s also very important to say that these asymptomatic cases were identified shortly after the relaxation of a very stringent lockdown in Wuhan that lasted more than 70 days. By then, the epidemic in Wuhan had been effectively brought under control.

“The virulence of Covid-19 may be weakening over time. And it is likely that the viral load of Wuhan’s asymptomatic cases may be low, compared with cases in locations with a high level of virus transmission.

“Antibody testing showed that almost two thirds of the asymptomatic cases had previously had Covid-19.

“Because the risk of residents being infected in the community was greatly reduced, when susceptible residents are exposed to a low dose of virus, they may tend to be asymptomatic as a result of their own immunity.

“So, it would be problematic to apply the results of our research to countries where Covid-19 outbreaks have not been successfully brought under control.

“Actually, the existence of asymptomatic cases remains a concern even in Wuhan. It is too early to be complacent, because of the existence of asymptomatic positive cases and high level of susceptibility in residents in Wuhan.

“Public health measures for the prevention and control of Covid-19 epidemic, including wearing masks, keeping safe social distancing in Wuhan should be sustained. And vulnerable populations with weakened immunity or co-morbidities, or both, should continue to be appropriately shielded.”

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‘Post-lockdown SARS-CoV-2 nucleic acid screening in nearly ten million residents of Wuhan, China’ is published in the journal Nature Communications.
https://www.nature.com/articles/s41467-020-19802-w

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