Category: COVID

Categories : COVID General InterestTags :

Ridhwaan Suliman on Twitter: Graphs, Insight and Empathy

On By ModernMedia
Photo by Tracy le Blanc from Pexels
Photo by Tracy le Blanc from Pexels

The Daily Maverick interviewed Dr Ridhwaan Suliman, a senior researcher at CSIR who has entered the spotlight by posting his concise, easy-to-understand COVID numbers graphs on Twitter.

Trained as a mechanical engineer and with a PhD in applied mathematics, he develops computational tools to model and simulate physical systems and processes. Equations in real-world contexts and how they govern physical systems are the relationships he translates into code. And from the code and modelling he can find solutions to make things work more optimally.

As a boy, he took apart his brothers’ old toys to see how they worked, and he took the same approach with COVID data to make sense of it. He started tracking the data in early 2020, and wanted to contribute in some way amidst all the growing uncertainty.

“When I started seeing the raw numbers that were being fed to us daily I couldn’t quite make sense of it myself because the raw numbers in isolation don’t show what’s happening, actually.”

As he tweeted his analyses, he drew attention for his concise summaries of the situation, and praise for helping people to understand the trends. However, he stresses that this is all unpaid, with nobody else’s agenda and that he is not a medical expert.

https://twitter.com/rid1tweets/status/1434570126091821062
This week’s update from Dr Ridhwaan

“I’m just comfortable with the numbers.” He gratefully turns to the science experts he engages with on Twitter because “there’s so much more to learn”, he says. That, and a lot of background reading, which he readily dives into.

Dr Suliman’s tracking of the data let him identify gaps and to add to the call for open data, better data collection and smarter analysis. This allows for the factoring in of more variables and laying out of better parameters. “Sure, data can be manipulated to fit a certain narrative, but the benefits outweigh the risks,” he says.

Even in the polarising, easily toxic world of Twitter, Dr Suliman’s interactions show a great empathy.

“We’ve all had numerous moments in this pandemic when things have been depressing and that’s probably something that doesn’t come out on Twitter because you’re generally only sharing things when things are hunky-dory, you don’t share when you’re not okay. There have been many times when I’ve just wanted to stop tweeting, but I get drawn back by people who reach out and say ‘you’re helping me’ – and that’s good enough reason to continue.”

Since he first started on Twitter, he has since appeared numerous times on television to explain the data behind COVID numbers.

Despite his newfound fame however, he looks forward to the time when he can travel again.  “I’ll trade the followers any day for our lives to go back to some sense of normality,” he says.

Source: Daily Maverick

Categories : COVIDTags :

Europe to Return Millions of Locally-filled J&J Vaccines

On By ModernMedia

The European Union has agreed to return millions of COVID vaccines doses partially produced in South Africa back to the African continent.

South Africa’s Aspen Pharmacare operates the plant that is partially producing Johnson & Johnson vaccines, where vaccine substance from Europe is sent to be bottled and shipped.

The plant is supposed to produce 400 million doses for the AU’s African Vaccine Acquisition Trust through 2022, to be purchased by African nations using World Bank financing. Shipments started in August, with 6.4 million doses delivered to countries, but they have been limited due to the manufacturing plant’s production capacity.

The announcement came as Africa struggles to immunise its population against COVID, partly due to a lack of supply resulting from wealthier countries buying up most vaccines, and also from widespread vaccine hesitancy. 

“All the vaccines produced at Aspen will stay in Africa and be distributed to Africa,” said Strive Masiyiwa, special African Union envoy. “This issue has been corrected and corrected in a very positive way.”

The announcement came after a meeting in Berlin between South African President Cyril Ramaphosa and European Commission President Ursula Von der Leyen, he said, adding that the first supplies were expected this month.

“In addition, the Europeans committed to give us 200 million doses before the end of December,” Masiyiwa said at the briefing by the Africa Centres for Disease Control and Prevention.

About 2.93% of people who have been fully immunised against COVID, said Africa CDC director John Nkengasong. The World Health Organization meanwhile warned that eight out of 10 African countries were likely to fall short of the “crucial” goal of vaccinating the most vulnerable 10% of their populations against COVID by the end of the month.

Source: Eyewitness News

Categories : COVIDTags :

New Antiviral Drug for COVID to Be Trialled in SA

On By ModernMedia
Source: CDC

Codivir, a new antiviral drug with promising effects against COVID, will be trialled in South Africa.

Following on from the phase I study’s successful completion, Code Pharma, a Dutch pharmaceutical company developing Codiviir, is starting phase II double-blind controlled study in Spain, Brazil, South Africa and Israel.

Codivir is a short synthetic 16 amino-acid peptide, originally derived from HIV peptides. Code Pharma discovered the peptide’s direct antiviral effect against SARS-CoV-2 after in vitro studies at the British virology research laboratory, Virology Research Services in London.

Codivir was tested in a phase I trial in São Paulo, Brazil, where researchers found that Codivir had a high safety profile while significantly suppressing viral replication in most of the fully assessed patients. All treated patients recovered quickly and no side effects often associated with COVID infections were seen. The results also indicated that Codivir might have a similar beneficial effect on other RNA viruses such as influenza.

Lead researchers from the Department of Medicine at Hadassah Medical Center, Dr Yotam Kolben and Dr Asa Kesler said the antiviral drug had potential for improving the current therapies for COVID.

“The pre-clinical data and the results of the clinical trial support the safety of Codivir administration in humans and suggest its significant anti-COVID effect,” the researchers said.

Professor Shlomo Maayan, director of the Infectious Disease division at the Barzilai Medical Center, said Codivir had a very good safety profile and an impressive antiviral effect, both in the lab and in the phase I clinical trials.

“We eagerly await the results of the double-blind studies using Codivir. It may be a breakthrough in the field of antiviral therapy for COVID patients,” said Prof Maayan.

Source: Biospace

Categories : COVID VaccinesTags :

MMR and Tdap Vaccines May Confer Some COVID Protection

On By ModernMedia
Source: Pixabay CC0

Mounting evidence shows that the Measles-Mumps-Rubella (MMR) and Tetanus-Diphtheria-Pertussis (Tdap) vaccines confer limited protection against COVID.

The MMR vaccine, given during early childhood, and Tdap vaccine, given every 10 years, elicit protective responses against the diseases they are designed for. It’s possible that they also elicit cross-reactive memory T cells that can respond to antigens that are present in other pathogens — including the viral antigens in SARS-CoV-2. The idea is that pre-existing memory T cells generated by prior MMR or Tdap vaccination and activated by SARS-CoV-2 infection give the immune system a head start in responding to SARS-CoV-2, lowering the risk of severe COVID.

To find out if the MMR and Tdap vaccines provide additional protection against COVID, researchers at Brigham and Women’s Hospital performed laboratory-based analyses with new techniques to detect and characterise T cell responses to antigens. They applied these techniques to measure T cell responses isolated from the blood of COVID convalescent patients and patients vaccinated against COVID to antigens from SARS-CoV-2 and the MMR and Tdap vaccines. They also leveraged a large, well-annotated cohort of COVID patients and found that prior MMR or Tdap vaccination was associated with decreased disease severity. Their results are published in Med.

“Our Cleveland Clinic colleagues observed an association where individuals with COVID who had either MMR or Tdap vaccines had a much lower frequency of going to the intensive care unit or dying,” said co-author Andrew Lichtman, MD, PhD, an immunologist and senior investigator in the Brigham’s Department of Pathology and professor of Pathology at Harvard Medical School. “Although previous smaller studies suggested a similar link, our in-depth epidemiological analyses, together with our basic research results, suggest that these commonly given vaccines may protect against severe disease.”

“During the COVID pandemic, we know that there was a marked decline in routine vaccinations for children and adolescents,” said corresponding author Tanya Mayadas, PhD, a senior scientist in the Brigham’s Department of Pathology and professor of Pathology at Harvard Medical School. “Our findings emphasise the importance of routine vaccination for children and adults. We know vaccines protect against devastating diseases, and we’re now seeing growing evidence that some of them provide a degree of protection against severe COVID disease.”

An unexpected observation jumpstarted the investigation. Prof Mayadas, her postdoctoral fellow Vijaya Mysore, PhD, and colleagues noted in lab experiments with COVID convalescent blood that whenever they observed a heightened T cell response to SARS-CoV-2 proteins, they also saw a heightened response to proteins from MMR and Tdap, which were controls. This was seen in both COVID convalescent and uninfected individuals vaccinated against SARS-CoV-2.

In a subsequent analysis, Prof Mayadas and colleagues teamed up with researchers at Cleveland Clinic to examine the epidemiological evidence. The Cleveland Clinic team performed a retrospective cohort study using data from more than 75 000 patients seen at the Cleveland Clinic Health System in Ohio or Florida who had tested positive for COVID between March 8, 2020, and March 31, 2021. A statistical analysis found that patients who had previously been vaccinated for MMR had a 38 percent decrease in hospitalisation and a 32 percent decrease in ICU admission/death. Patients previously vaccinated for Tdap had 23 percent and 20 percent decreased rates, for these outcomes, respectively.

“Beyond learning about the potential benefits of the MMR and Tdap vaccines in the context of COVID, this study provides a blueprint for accelerating research,” said co-author Lara Jehi, MD, MHCDS, Chief Research Information Officer of the Cleveland Clinic Health System. “Biomedical hypotheses generated in the laboratory can be explored through robust clinical and epidemiological research in well-curated, real-world data such as the Cleveland Clinic COVID Registry. Knowledge learned through this collaboration is much more than the sum of our individual parts.”

The authors note that epidemiological observations strengthen their lab findings, more work is needed to find a causal association between the MMR and Tdap vaccinations and severity of COVID disease.

“With regards to COVID vaccines, our findings predict that although MMR and Tdap are not a substitute for COVID vaccines they may afford greater and more durable protection, possibly against emerging spike variants than the COVID vaccine alone,” said Prof Mayadas. “And in areas where the COVID vaccines are not available, they could protect infected individuals from developing severe disease.”

Source: Brigham and Women’s Hospital

Categories : COVIDTags :

August Poll Results; 18-34s Upbeat on Vaccines

On By ModernMedia
Photo by Mufid Majnun on Unsplash

To date, nearly 12 600 000 vaccinations have been administered in South Africa, with 23.66% of the adult population now fully vaccinated. Quicknews’ August poll revealed that 44% of site visitors felt that the government’s COVID vaccine rollout was “Acceptable”, while 51% felt it was either “Poor” or “Very Poor”. Only 5% rated it “Good” or “Very Good”.

The Department of Health’s COVID-19 and Vaccine Social Listening Report finds that the demand for vaccination had increased, with around 250 000 daily jabs, fuelled by a surge by the recent eligibility of the 18 – 34 age group. The report highlights include:

  • Social media conversations are more positive about the vaccine rollout with improved services, such as free transport and pop-up vaccination sites. Barriers to vaccination seem now to be more of an issue than vaccine hesitancy. It is noticeable that most anti-vax videos originated from other countries (especially the US), while most pro-vax are local (eg celebrating being vaccinated).
  • While vaccination is met with eagerness and discussion among the 18 – 34 age group, they also still appear to be the most vaccine-resistant age group, believing themselves to be healthy and not needing a vaccine. Discussion over whether vaccines should be mandatory is ongoing, eg to go to concerts, with some disinformation suggesting that it is already happening, and a sign of control by the state.
  • There has been increasing media coverage supportive to vaccines. The Department of Health’s vaccine demand acceleration plan has been met positively, as well as favourable coverage of the FDA’s full approval of the Pfizer vaccine. 
  • However, there are some negative views of the government’s vaccine prioritisation, and is seen as neglecting basic services such as sanitation and public transport. 
  • A WhatsApp survey run by Praekelt.org suggests that 90% of 4,000 people who had been vaccinated are willing to encourage others to do so. People reportedly have more rational concerns about vaccines (efficacy, side effects, developed so quickly, reports of deaths) and not the wilder conspiracy theories (eg tracking devices, depopulation).
  • Disinformation and problematic statements such as those from Rev Kenneth Meshoe vaccine-resistant statements and support for anti-vaxxers Dr Susan Vosloo and Prof Tim Noakes have undermined vaccine trust.
  • There is some debate over preferences over currently available vaccines or those that may be available later, eg Astra Zeneca, Sinovac. Confusion on reports that J&J second dose might be required and other booster shots.
  • The report notes some anti-vaccination sentiment in the Muslim community, with messages circulated that vaccines are haram (forbidden by Sharia law), though most Muslim authorities produce responsible evidence-based views.

Source: SA Coronavirus Portal

Categories : COVIDTags :

What is The C.1.2 Variant?

On By ModernMedia
Image by Quicknews

A preliminary study recently uploaded on the medRxiv preprint server, researchers detail the detection and characteristics of the C.1.2 variant of SARS-CoV-2, which has not yet been assigned a variant of interest (VOI) status, but which could potentially have increased transmission and immune escape potential.

The researchers describe how they identified a new SARS-CoV-2 variant, C.1.2. The first detection of this variant was during the third wave of infections in South Africa from May 2021 onwards, and has also been detected in seven other countries around the world.

New SARS-CoV-2 variants are commonly associated with new waves of infection. Like several other variants of concern (VOCs), C.1.2 has accumulated a number of substitutions beyond what would be expected from the background SARS-CoV-2 evolutionary rate. This suggests the likelihood that these mutations arose during a period of accelerated evolution in a single individual with prolonged viral infection through virus-host co-evolution. Deletions within the N-terminal domain have been evident in cases of prolonged infection, further supporting this hypothesis.

C.1.2 contains many mutations that have been identified in all four VOCs (Alpha, Beta, Delta and Gamma) and three VOIs (Kappa, Eta and Lambda) as well as additional mutations. Many of the shared mutations have been associated with improved ACE2 binding or furin cleavage, and reduced neutralisation activity, raising concern about the transmission potential of this variant. The next step is determining the functional impact of these mutations and to find out if they give it a replication advantage over the Delta variant.

The C.1.2 lineage is continuing to grow, and as of 20 August 2021, there were 80 C.1.2 sequences in GISAID, and the variant has now been detected in Botswana and in the Northern Cape of South Africa. Note that this study is yet to have the peer review process completed.

Source: MedRxiv

Categories : COVIDTags :

The Evidence for The Animal Origins of COVID

On By ModernMedia
Photo by Todd Cravens on Unsplash

An article in Science explores the evidence for the animal origin of COVID, which was first detected in December 2019, but inferred to be present in Hubei province, China, for about a month beforehand. 

The current COVID epidemic can be better understood by examining the severe acute respiratory syndrome coronavirus (SARS-CoV) outbreak which began in 2002. Investigations later found that horseshoe bats (Rhinolophus) in China harboured related coronaviruses. It was inferred that a sarbecovirus circulating in horseshoe bats seeded the progenitor of SARS-CoV in an intermediate animal host, most probably civet cats Although other possible intermediate hosts for SARS-CoV were identified, it is a population of civet cats within markets that appear to have acted as the conduits of transmission to humans from the horseshoe bat reservoir of SARS-CoV. Presumably a captive civet cat initially became infected by direct contact with bats or was infected before capture.

SARS-CoV-2 first emerged in Wuhan city, over 1500 km from the closest known naturally occurring sarbecovirus collected from horseshoe bats in Yunnan province. Coronaviruses genetically close to SARS-CoV-2 are circulating in horseshoe bats with wide geographic ranges indicate that the singular focus on Yunnan is misplaced. Confirming this assertion, the evolutionarily closest bat sarbecoviruses are estimated to share a common ancestor with SARS-CoV-2 at least 40 years ago, showing that these Yunnan-collected viruses are highly divergent from the SARS-CoV-2 progenitor. 

Though the virus may have jumped to humans from direct horseshoe bat–to–human contact, a known risk for SARSr-CoVs, the first detected SARS-CoV-2 cases in December 2019 are associated with Wuhan wet markets. This is consistent with multiple animal-market–associated spillover events in November and December (9). It is currently not possible to be certain of the animal source of SARS-CoV-2, but it is notable that live animals, including civet cats, foxes, minks, and raccoon dogs, all susceptible to sarbecoviruses, were for sale in Wuhan markets, including the Huanan market (identified as an epicenter of the outbreak in Wuhan) throughout 2019.

Together, this suggests a central role for SARSr-CoV–susceptible live intermediate host animals as the primary source of the SARS-CoV-2 progenitor that humans were exposed to, as was the case with the origin of SARS.

Spillover events are not so rare, indicated by evidence of SARSr-CoV–specific antibodies in people living in rural areas, and even higher rates recorded in people living near bat caves. When exposed a densely packed human population, such as in Wuhan city, these spillover events have a much higher chance of resulting in substantial onward spread 

Interestingly, the proximity of humans to wildlife may have been increased by demand for alternative meat sources caused by reduced availability of pork in 2019. This was caused by the African swine fever virus (ASFV) pandemic, which led to ∼150 million pigs being culled in China, resulting in a pork supply reduction of ∼11.5 million tonnes in 2019, and from which the country is still recovering. Increased use of cold-chain logistics in the wake of the ASFV pandemic means that frozen animal carcasses carrying SARS-CoV-2 may have been brought from much farther afield.

Once crossed over, SARS-CoV-2 readily established itself in humans by being a generalist, as opposed to being specialised for humans. Ironically, since humans are now the largest reservoir of the virus, animals in contact with humans are at risk of virus spillover. The article authors closed by stressing the need for much greater viral surveillance to spot emerging threats, as current coverage is extremely spotty.

Source: Science

Categories : COVIDTags :

Delta Variant More than Doubles Hospitalisation Risk

On By ModernMedia
Source: Mat Napo on Unsplash

In a study of more than 40 000 COVID cases, those infected with the delta variant have about twice the hospitalisation risk as those infected with the alpha variant. The findings were published in The Lancet Infectious Diseases.

The risk of hospitalisation or emergency hospital care within 14 days of infection with the delta variant was 1.45 times greater than the alpha variant. This is the first study reporting hospitalisation risk for the delta versus alpha variants based on cases confirmed by whole-genome sequencing.

Dr Gavin Dabrera, one of the study’s lead authors and a Consultant Epidemiologist at the National Infection Service, Public Health England, said: “This study confirms previous findings that people infected with Delta are significantly more likely to require hospitalisation than those with Alpha, although most cases included in the analysis were unvaccinated.”

The delta variant emerged in India in December 2020 and early studies found it to be up to 50% more transmissible than the alpha variant, which first appeared in the UK. A preliminary study from Scotland previously reported a doubling of hospitalisation risk with the delta variant over the alpha variant and it is suspected that delta is associated with more severe disease. The previous study used patients’ initial PCR test results and determined which variant they had by testing for a specific gene that is more common in the delta variant.

The researchers analysed healthcare data from 43 338 COVID-positive cases in England between 29 March and 23 May 2021. During the study period, there were 34 656 cases of the alpha variant (80%) and 8682 cases of the delta variant (20%). While the proportion of delta cases in the study period overall was 20%, it eventually encompassed two thirds of new COVID cases in the week starting 17 May 2021 (65%), effectively becoming the dominant strain in England.

Around one in 50 patients were admitted to hospital within 14 days of their first positive COVID test (2.2% alpha cases; 2.3% delta cases. After accounting for factors that are known to affect susceptibility to severe illness from COVID, including age, ethnicity, and vaccination status, the researchers found the risk of being admitted to hospital was more than doubled with the delta variant compared with the alpha variant (2.26-fold increase in risk).

It has been shown in multiple studies that full vaccination prevents both symptomatic infection and hospitalisation, for both alpha and delta variants. Indeed, in this study, only 1.8% of COVID cases (with either variant) had received both doses of the vaccine; 74% of cases were unvaccinated, and 24% were partially vaccinated. With the small number of vaccinated people being hospitalised, it is not possible to statistically compare hospitalisation risk between alpha and delta in such cases, so the results of the study apply to unvaccinated or partially vaccinated cases.

One of the study’s lead authors, Dr Anne Presanis, Senior Statistician at the MRC Biostatistics Unit, University of Cambridge, said: “Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic. Getting fully vaccinated is crucial for reducing an individual’s risk of symptomatic infection with Delta in the first place, and, importantly, of reducing a Delta patient’s risk of severe illness and hospital admission.”

Limitations to the study included some demographic groups possibly being more likely to seek hospital care, which could have biased the results, and there may have been changes in hospital admission policy during the period of the study, although adjustment for demographics and calendar time should have minimised such bias. The authors also did not have access to information about patients’ pre-existing health conditions, which are known to affect the risk of severe illness from COVID. By using age, gender, ethnicity, and estimated level of socioeconomic deprivation, they were able to account for this.

Source: Medical Xpress

Categories : COVIDTags :

A KZN Doctor’s Observations and Treatments of COVID

On By ModernMedia
SARS-CoV-2 viruses (yellow) infecting a human cell. Credit: NIH

Dr Shankara Chetty, a general practitioner with a natural science background in genetics, advanced biology, microbiology and biochemistry, has been critically reviewing information that has arisen from observations of the COVID pandemic from around the world. Knowledge gained from a broad natural science background convinced him that there was a missing element in these reports. This is a summary of an article published in Issue 5 of Modern Medicine in 2020.

“A wealth of knowledge of hospital presentations, pathology and investigations has been generated, but there has been a distinct lack of information regarding initial presentation, progression and pathogenesis,” said Dr Chetty.

Type 1 hypersensitivity reaction
When COVID arrived in South Africa, Dr Chetty isolated himself so as to limit interactions with family and the public and erected a tented field clinic in his practice parking so as to be able to examine and follow up on every COVID patient without risk to his other patients. According to him he had a theoretical understanding of the possible pathogenesis but needed to verify his suspicions.

“From the examination, treatment and follow up of over 200 symptomatic COVID patients, it is my opinion that COVID illness has two aetiologies. It is initially a respiratory viral infection with typical symptoms, progression and outcomes over the initial 7 days. On around day 7, a Type 1 hypersensitivity reaction is triggered in those that are sensitive, leading to the sequelae typically seen on admission.

“This reaction causes the release of chemical mediators in the ling, resulting in inflammation, oedema, and in time, massive cell damage. The resultant cellular disruption is what triggers the ‘cytokine storm’ in an attempt to repair damaged cells and remove debris. This release of cytokine produces the variety of pathologies that are seen,” said Dr Chetty.

Rapid response to treatment
His treatment protocol included the use of hydrochloroquine, azithromycin and doxyclcline to combat the viral component and antihistamines, leukotriene receptor antagonists and steroids, amongst others, for the Type 1 hypersensitivity reaction. This protocol produced consistent outcomes, no sequelae, and rapid recovery of all patients. In all, they had no deaths, no hospitalisations and recover of all patients, regardless of age, within 14 days.

“Outcomes of identifying and treating a Type 1 hypersensitivity reaction were most telling in the more severe dyspnoiec patients, with saturations below 85% on presentation that had improvement to over 95% in 24 hours, with outpatient management on room air, negating the need for oxygen or hospitalisation,” said Dr Chetty.

According to Dr Chetty, the rapid response to these medications used to treat Type 1 hypersensitivity reactions confirmed its existence. This could have some serious implications for the future management of the COVID pandemic. Monitoring for a hypersensitivity reaction and prompt treatment would decrease morbidity and mortality significantly.

Source: Modern Medicine

Categories : COVIDTags :

Viral Load Alone not Indicative of COVID Transmission Risk

On By ModernMedia
SARS-CoV-2 viruses (yellow) infecting a human cell. Credit: NIH

Viral load as determined by cycle threshold (Ct) has limited utility in guiding decisions regarding isolation and quarantine of COVID patients, according to a study of COVID cases in university students.

Though some in vitro studies indicate that virus load levels in infected individuals affects the successful rate of virus transmission, whether the viral load carried at the individual level can determine transmissibility was unknown. In this study published in The Journal of Molecular Diagnostics, university students underwent regular testing and contact tracing after positive tests, and significant overlap in cycle thresholds (Ct) was found between spreaders and nonspreaders. This brings into question using Ct values to determine transmission rates, with even those with low viral loads able to transmit the virus.
Real-time RT-PCR Ct values represent the number of amplification cycles required for the target gene to exceed a threshold level. Ct values are therefore inversely related to viral load and can provide an indirect method of quantifying the copy number of viral RNA in the sample; however, the use of Ct values as a proxy of viral load is influenced by the assay itself (correlation would stand in the linear dynamic range of the specific RT-PCR assay used) and factors within the sample matrix that can affect amplification efficiency

“We wanted to find whether there was a scientifically sound way to quickly triage students with potential high-risk exposure to COVID positive students for quarantine,” explained co-lead authors Patrice Delafontaine, MD, Department of Medicine, and Xiao-Ming Yin, MD, PhD, Departments of Pathology and Laboratory Medicine, Tulane University School of Medicine. “Some studies have found that the Ct value of the RT-PCR assay is a surrogate for infectivity, and cutoff Ct values have been proposed as a way to guide isolation practices. Through testing and contact tracing, we found that Ct value could not predict transmissibility. We should not overlook positive patients with low viral load, and all positive patients should be quarantined.”

A high-throughput SARS-CoV-2 surveillance testing program was established at Tulane University to support isolation and contact tracing efforts at the campus. Students were tested twice weekly and asked about symptoms they may be experiencing. Contact tracers spoke to all positive case subjects to identify close contacts.
The study looked at 7440 patients who were screened between September 1, 2020 and October 31, 2020, among whom 602 positive cases were identified. From this group, 195 index cases were identified with one or more reported close contacts, who were then tested during their mandated 14-day quarantine period for evidence of transmission from the associated index cases. Of these index cases, 48.2% had at least one contact who became COVID positive, whereas 51.8% of the index cases were nonspreaders with no contacts who subsequently tested positive. Mean Ct values of the spreaders and the nonspreaders were nearly identical.

The researchers then reversed approach, where index cases were traced for 481 students undergoing quarantine due to known exposure to the disease. Eighteen percent of the students became positive during their quarantine. Index cases for the 481 quarantined students were considered spreaders if they were linked to one or more quarantine students with a positive test result, or nonspreaders if they were associated only with students with negative test results. Mean Ct values of the spreader and the nonspreader groups were similar.

The researchers next identified and evaluated 375 positive cases to assess the relationship between symptom presentation and Ct values. Reported symptoms included lethargy, fever, headache, cough, runny nose and gastrointestinal symptoms. Mean and median Ct values were lower in symptomatic cases than in asymptomatic cases, indicating a higher viral load, This suggests that infections with a higher viral load could more often lead to symptom development, or that symptomatic individuals tend to have higher viral loads or maintain their viral loads for a longer period of time. Ct levels may be useful at a population level, in association with symptomatic presentation, to indicate the likelihood of transmission. These values may thus have epidemiologic or surveillance importance.

“Taken together, these index cases suggest that Ct values alone do not predict transmission risk and reporting of Ct values at the individual level, such as by setting a cutoff value of 32, would provide little diagnostic value for case management,” note Dr. Delafontaine and Dr. Yin. “A sensitive and robust SARS-CoV-2 diagnostic testing method is needed to effectively control viral transmission by maximizing the ability to identify and quarantine even those with a low level of virus.”

Source: Elsevier