Day: February 18, 2022

Categories : COVID Expert OpinionTags :

An Estimated 70% of South Africans Have Had COVID

On By ModernMedia
Image by Quicknews

Writing for GroundUp, Dr Alex Welte unpacks the results of the latest blood donor survey, which suggests that some 70% of South Africans have had a COVID infection.

The South African National Blood Service (which handles the blood supply for eight provinces) and the Western Cape Blood Service have been testing some donors for Covid antibodies over the last year or so. This has contributed to our understanding of how many people have been infected by SARS-CoV-2 (the virus that causes Covid), and what proportion of infections lead to death. It may help us plan for future waves, though exactly how is complicated.

On the assumption that another wave towards the end of 2021 was nearly inevitable – but before we all heard about omicron – it was decided to perform more such testing in early November. The numbers are now out.

The headline results are:

  • Overall about 80% of black donors had previously had Covid, and 40% of white donors.
  • There is no meaningful variation between age groups and sexes.
  • This latest survey did not include Western Cape data.
  • The test used does not detect the antibodies produced in response to vaccination, so this really is an estimate of people who have been infected.

While blood donors are not perfectly representative of the country’s population, we can take into account differences between the racial breakdown of the donor population and the racial breakdown of the general population. This means that our face-value national estimate is that about 70% of people had been infected before the omicron wave hit.

Since then we’ve had the omicron wave. We would very much like to know how many people are infected now, but there’s really no simple way to derive this number. Researchers are now updating their models with this additional piece of data, and we may see some estimates soon.

With that caution, here is my back-of-the-envelope estimate:

  • Omicron seems to have little trouble infecting people who have been infected by other variants, though there is some protection from prior infection and vaccination.
  • By late last year, quite a bit more than half the population had already had a prior infection.
  • Hence, I estimate that about half of the omicron wave infections were in previously uninfected individuals.
  • Given the infection detection rate estimates from previous waves, and a number of plausible sources of possible variation in this rate, I estimate the detection rate at about 1 in 10.
  • Given the roughly 700 000 cases reported between mid November and mid February, we get an estimate of 7 million cases, and therefore 3.5 million new infections.
  • Given our population of about 60 million, this is roughly an additional 6%.
  • Bottom line: it’s not crazy to estimate that about three-quarters of South Africans have by now been infected. But I would not be surprised if serious models come up with even higher estimates.

A troubling result of the survey is that once more it shows the serious racial disparities in South Africa. I don’t know if this carried over to the omicron wave. Estimating the racial breakdown of infection after omicron depends in a complicated way on variations in housing, lifestyle, access to vaccination, and all the usual factors that shape daily life in our country.

Dr Welte helped design and implement the blood donor survey.

Source: GroundUp

Categories : Neurodegenerative DiseasesTags :

Peptide Discovery Could Halt Nerve Degeneration

On By ModernMedia
A healthy neuron.
A healthy neuron. Credit: NIH

Promising results have been found in the quest for a treatment to halt nerve cell degeneration in disorders like Parkinson’s disease, by preventing their mitochondria from breaking apart with a particular peptide.

The research, published in Brain, examined how the long axons that carry messages between nerve cells in the brain can break down, which causes increasingly worse tightening of the leg muscles, leading to imbalance and eventually paralysis, in addition to other symptoms.

Animal studies have shown it may be a problem with the mitochondria that leads to the axons breaking down or not growing long enough. Since studying human nerve cells is difficult, the researchers made use of human stem cells they modified to become nerve cells with the genetic disorder for a particular type of hereditary spastic paraplegia.

“What we found was that the mitochondria in these cells were breaking apart, what we call mitochondrial fission, and that caused the axons to be shorter and less effective at carrying messages to the brain,” study leader Prof Xue-Jun Li said. “We then looked at whether a particular agent would change the way the nerve cells function — and it did. It inhibited the mitochondrial fission and let the nerve cells grow normally and also stopped further damage.”

What this means for the thousands of people affected by this type of genetic disorder is that this peptide could prove to be useful for a drug or other therapy to stop the nerve cells from becoming damaged or possibly even reverse the course of the damage. Additionally, gene therapy could also prevent mitochondrial damage, the researchers suggested, which would provide another strategy to reverse the nerve damage.

Source: University of Illinois Chicago

Categories : Implants and Prostheses UncategorizedTags :

Recipients of Bionic Eyes Blindsided by Obsolescence

On By ModernMedia
Source: Daniil Kuzelev on Unsplash

After the manufacturer of a bionic eye ended support, hundreds of recipients of the vision-improving implants have been left without support – “literally in the dark”, as one of them put it.

IEEE Spectrum, which first broke the story, reported that Second Sight discontinued its retinal implants in 2019. The retinal implants serve as the source of artificial vision for the users.

The publication wrote that the firm’s focus is currently on developing a brain implant known as the Orion, which also provides artificial vision. However, it only offers very limited support to the 350 or so who have the now-obsolete Argus II implants.

The system consists of a camera mounted on glasses worn by the user, which transmits video to a video processing unit (VPU), which then encodes the images into arrays of black and white pixels. The VPU then relays the pixel to an electrode array behind the retina, which creates flashes of light corresponding to the white pixels. The technology has had a long and costly road from experiment to product, starting with a lab experiment in the 1990s where stimulation of a single electrode in the retina was discovered to create a visible flash of light perceived by a blind patient. It is hugely expensive, with an estimated cost of $150,000 (R2.25 million) even before the surgery and post-surgery training. 

Implantation surgery typically takes a few hours, followed by training to help users interpret the new optical input from their implants. It is not a replacement for sight; rather it is more like a new sense. Users of the system see fleeting changes of grey which some can then use to assist with basic locomotion. However, the technology is still crude and not all benefit to the same degree. While some can make out the stripes on a pedestrian crossing, others never achieve that level of ability.

The technology also comes with some risk. In the postapproval period, 17% experienced adverse events, though this was an improvement over the 40% in the preapproval period. Since the implant can interfere with MRI scans, some have had to consider removal.

IEEE Spectrum contacted a number of patients, who voiced concern over their future. One patient, Ross Doer, said he was delighted when Second Sight told him in 2020 he was eligible for software upgrades. Yet, he heard troubling rumours. When he called his Second Sight vision-rehab therapist, “She said, ‘Well, funny you should call. We all just got laid off,’ ” he recalled. “She said, ‘By the way, you’re not getting your upgrades.’ ”

“Those of us with this implant are figuratively and literally in the dark,” he said.

Second Sight, when contacted by the publication, said that it had to reduce its workforce because of financial difficulties, and though it attempted to provide “virtual support” was unable to assist with repairs or replacements.
Benjamin Spencer, one of the six patients to receive the new Orion implant, said that it was “amazing” and he was able to see his wife for the first time. But knowing what he does now about Second Sight makes him apprehensive, and plans to have his implant removed at the end of the study period.

Speaking to the BBC, Elizabeth M. Renieris, professor of technology ethics at the University of Notre Dame, in the US, described the development as a cautionary tale.

“This is a prime example of our increasing vulnerability in the face of high-tech, smart and connected devices which are proliferating in the healthcare and biomedical sectors,” she said.

“These are not like off-the-shelf products or services that we can actually own or control. Instead we are dependent on software upgrades, proprietary methods and parts, and the commercial drivers and success or failure of for-profit ventures.”

She added that in future, ethical considerations concerning such technology should include “autonomy, dignity, and accountability”.

Source: IEEE Spectrum

Categories : Cardiovascular DiseaseTags :

New Blood Thinners from Tick Saliva

On By ModernMedia
Source: Wikimedia CC0

Researchers looking for new anti-clotting drugs have discovered a unique class of medications that act as blood thinners by inhibiting an enzyme in the genes of tick saliva.

The study, published in Nature Communications, focused on novel direct thrombin inhibitors (DTI) from tick salivary transcriptomes, or messenger RNA molecules expressed by an organism. As a result of  the research, there are now new anticoagulant medications that can be developed for the treatment of patients with a variety of coronary issues, including heart attacks.

“Interest in ticks as a model for developing drugs that prevent blood clotting – [often] the cause of heart attacks and strokes – is firmly rooted in evolutionary biology,” said Professor Richard Becker, a co-author of the study.

“Analysis of backbone structures suggest a novel evolutionary pathway by which different blood clot inhibiting properties evolved through a series of gene duplication events. Comparison of naturally occurring blood clot inhibitors of differing tick species suggests an evolutionary divergence approximately 100 million years ago.”

Prof Becker and his international colleagues discovered DTIs from tick salivary transcriptomes and optimised their use as a pharmaceutical. The most potent is a key regulating enzyme in blood clot formation with very high specificity and binding capacity that is almost 500 times that of bivalirudin, a drug used during a typical nonsurgical procedure used to treat narrowing of the coronary arteries. Those minimally invasive procedures are performed in roughly 1 million persons yearly in the United States.

“Despite their greater ability to reduce the incidence of the formation of blood clots, the drugs demonstrated less bleeding, achieving a wider therapeutic index in nonhuman models,” Becker says. “The higher potency of the drug means it’s not necessary to use a lot of it in treating patients, which holds the cost of goods and manufacturing down.”

According to Prof Becker, tick saliva, as in other blood-feeding such as mosquitoes, contains pharmacological and immunological active compounds, which modulate immune responses and induce antibody production. This research leveraged an understanding of tick-host interactions and antibody formation.

“The holy grail of anticoagulant therapy has always been specificity, selectivity, efficacy and safety,” said Prof Becker. “Clinician-scientists must have the training and an environment that embraces asking questions and finding solutions, including those potential found deep within nature. An ability to both measure and adjust the drug dose and rapidly reverse its effects is particularly important for safety purposes. The next step is to complete pharmacology, toxicology, drug stability and other important regulatory steps before conducting clinical trials in humans.”

Source: University of Cincinnati

Categories : CancerTags :

New Recommendations for Earlier Breast Cancer MRI Screening

On By ModernMedia
This screening MRI detected a very small cancer (circled) in the patient’s breast.
Credit: Dr. Kathyrn Lowry

Annual MRI screenings starting at ages 30 to 35 may slash breast-cancer mortality by more than 50% among women with genetic changes in three genes, according to a study published in JAMA Oncology.

The pathogenic variants are in the ATM, CHEK2 and PALB2 genes – which collectively are as prevalent as the much-reported BRCA1/2 gene mutations. The study authors state that their findings support earlier MRI screening in these women.

“Screening guidelines have been difficult to develop for these women because there haven’t been clinical trials to inform when to start and how to screen,” said lead author Dr Kathryn Lowry.

The work was a collaboration of the Cancer Intervention and Surveillance Modeling Network (CISNET), the Cancer Risk Estimates Related to Susceptibility (CARRIERS) consortium, and the Breast Cancer Surveillance Consortium.

To arrive at their model, the researchers input age-specific risk estimates from CARRIERS involving some 64 000 women and recent published data for screening performance.

“For women with pathogenic variants in these genes, our modeling analysis predicted a lifetime risk of developing breast cancer at 21% to 40%, depending on the variant,” Dr Lowry said. “We project that starting annual MRI screening at age 30 to 35, with annual mammography starting at age 40, will reduce cancer mortality for these populations of women by more than 50%.”

The simulations compared the combined performance of mammography and MRI against mammography alone, and projected that annual MRI conferred significant additional benefit to these populations.

“We also found that starting mammograms earlier than age 40 did not have a meaningful benefit but increased false-positive screens,” Dr Lowry added.

Results from CISNET models have informed past guidelines, including the 2009 and 2016 U.S. Preventive Services Task Force recommendations for breast cancer screening in average-risk women.

“Modelling is a powerful tool to synthesise and extend clinical trial and national cohort data to estimate the benefits and harms of different cancer control strategies at population levels,” said senior author Dr Jeanne Mandelblatt.

The study projected about four false-positive screening results and one to two benign biopsies per woman over a 40-year screening span, the authors noted.

To get any benefit from genetic susceptibility-based screening guidelines, a woman would have to know beforehand that she carries the gene, yet most often a genetic test panel is done after a positive cancer result – too late for any benefit.

“People understand very well the value of testing for variants in BRCA1 and BRCA2, the most common breast cancer predisposition genes. These results show that testing other genes, like ATM, CHEK2, and PALB2, can also lead to improved outcomes,” said senior author Dr Mark Robson.

The researchers hope their analysis will aid the National Comprehensive Cancer Network (NCCN), the American Cancer Society and other organizations that issue guidance for medical oncologists and radiologists.

“Overall what we’re proposing is slightly earlier screening than what the current guidelines suggest for some women with these variants,” said senior author Professor Allison Kurian. “For example, current NCCN guidelines recommend starting at age 30 for women with PALB2, and at 40 for ATM and CHEK2. Our results suggest that starting MRI at age 30 to 35 appears beneficial for women with any of the three variants.”

Source: University of Washington