Scientists identify six distinct clusters of COVID-19 symptoms in patients

LONDON: Scientists have claimed that there are six distinct ''types'' of COVID-19, each distinguished by a particular cluster of symptoms in patients, findings, if validated, can help physicians better diagnose and monitor those infected with the novel coronavirus. The yet-to-be peer reviewed study, published in the medRxiv preprint platform, used a machine learning algorithm to analyse data from a subset of around 1,600 users in the UK and US with confirmed COVID-19, who had regularly logged their symptoms using the app in March and April. It analysed if particular symptoms appeared together, and how this was related to the progression of the disease. According to the scientists, led by those from King's College London in the UK, the findings have major implications for the clinical management of COVID-19 patients. "These findings have important implications for care and monitoring of people who are most vulnerable to severe COVID-19," said Claire Steves, a co-author of the study from King''s College London. They said the research can also help doctors predict who is most at risk and likely to need hospital care in a second wave of coronavirus infections. The study noted that patient symptoms can fall under one of the six following categories: ''flu-like' with no fever, ‘flu-like' with fever, gastrointestinal, severe level one with fatigue, severe level two with confusion, and severe level three accompanied by abdominal and respiratory pain. In the first category of patients who reported ''flu-like symptoms with no fever, the scientists said the manifestations included loss of smell, muscle pains, cough, sore throat, chest pain, but no fever. According to their analysis, those in the second category had headache, loss of smell, cough, sore throat, hoarseness, fever, and loss of appetite, and those in the gastrointestinal symptoms cluster had a combination of headache, loss of smell, loss of appetite, diarrhea, sore throat, chest pain, but no cough. Under the ''severe level one with fatigue'' category, the scientists said patients reported loss of smell, cough, headache, fever, hoarseness, chest pain, and fatigue, and those with the level two of severity expressed these same symptoms with the addition of loss of appetite, sore throat, confusion, and muscle pain. In the most severe category, the study noted that patients experienced headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain, shortness of breath, diarrhea, and abdominal pain. According to the research, all people reporting symptoms experienced headache and loss of smell, with varying combinations of additional symptoms at various times. It said some of the manifestations, such as confusion, abdominal pain and shortness of breath, are not widely known as COVID-19 symptoms, yet are hallmarks of the most severe forms of the disease. The scientists also analysed if people experiencing particular symptom clusters were more likely to require breathing support in the form of ventilation or additional oxygen. They discovered that only 1.5 per cent of people with cluster one, 4.4 per cent of those with cluster two and 3.3 per cent in cluster 3 required breathing support. For clusters four, five, and six, the researchers said these figures were 8.6, 9.9, and 19.8 per cent respectively. Nearly half of the patients in cluster six, according to the study, ended up in hospital, compared with just 16 per cent of those in cluster one. People with cluster four, five or six symptoms tended to be older and frailer, and were more likely to be overweight, the scientists said, adding that these patients had pre-existing conditions such as diabetes or lung disease than those in the other types. "If you can predict who these people are at day five, you have time to give them support and early interventions such as monitoring blood oxygen and sugar levels, and ensuring they are properly hydrated -- simple care that could be given at home, preventing hospitalisations and saving lives," Steves said. Carole Sudre from King''s College London, one of the lead scientists part of the study, said the research illustrates the importance of monitoring symptoms over time to make predictions about individual risk and outcomes more sophisticated and accurate. "This approach is helping us to understand the unfolding story of this disease in each patient so they can get the best care," Sudre said. "Being able to gather big datasets through the app and apply machine learning to them is having a profound impact on our understanding of the extent and impact of COVID-19, and human health more widely," added Sebastien Ourselin, a senior author of the study from King's College London. Copyright © Jammu Links News, Source: Jammu Links News
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Quantum Cheshire cats: A physics trick that separates the feline from its grin


K. S. Jayaraman: In the physical world, an object can not be separated from its properties. For instance, a smile and the resultant dimples on the cheeks are unique signatures that cannot be segregated from a person's body.

But it is not always so in the quantum world where the physical properties of a particle may not belong to the particle itself.

Quantum physicists Arun Kumar Pati and Debamalya Das from the Harish-Chandra Research Institute (HRI) in Allahabad now prove that a quantum object can permanently discard a physical property and obtain a new one it did not initially have1. "This sounds strange, but can have profound implications for our understanding of the quantum world," Pati told Nature India.

In quantum physics parlance, separating an object from its own properties is interestingly called the Quantum Cheshire Cat (QCC) effect — drawing inspiration from Lewis Carroll’s famous book "Alice in Wonderland", in which Alice is wonder struck by a magical cat that appears and disappears at will leaving its weak grin behind.

'All right', said the Cat; and this time it vanished quite slowly, beginning with the end of the tail, and ending with the grin, which remained some time after the rest of it had gone.

'Well! I've often seen a cat without a grin', thought Alice, 'but a grin without a cat! It's the most curious thing I ever saw in my life!' 

-- from Alice in Wonderland.

In 2013, Israeli physicist Yakir Aharonov and his colleagues showed the possibility of separating an object from its own properties using the concept of "quantum weak measurement" thereby supporting the QCC effect theory2.

In what they call a "thought experiment", Pati and Das now propose that two photons — tiny elementary particles — can swap their polarisations (or spins) even if they are not at the same site. They consider the photons as Cheshire cats, and their polarisations as the grins.

They revealed this separation of the body and the grin of the 'elementary Cheshire cats' by taking two sets of "weak measurements" of the particles — one to establish the location of the particle and the other to locate its spin (grin).

"Physical attributes are not real and may not belong to a system", Pati explains their observations. The thing at play here was 'quantum entanglement', meaning the inextricable linking of two particles in which whatever happens to one immediately affects the other. "Entanglement plays a crucial role in the realization of this exchange process," Pati says. This means that it is possible to swap the polarizations of two photons without their being close to each other. 

A schematic representation of exchange of grins in a double Quantum Cheshire Cat setup using 'weak measurement'.

© Pati, A. K. et al

QCC has opened up a new window for the understanding of quantum systems, quantum information as well as in technological applications, adds Pati. It pertains not only to photons and their polarizations but can, in principle, be observed with any quantum system and its property, such as neutron and its magnetic moment and electron and its charge.


Dipankar Home, a quantum physicist at Bose Institute in Kolkata, says implications of QCC effect are much debated and an unambiguous empirical demonstration of this effect still remains to be seen. "This work is a stimulating twist and its implications need to be further explored," he told Nature India.

Pati says the spin swapping by photons predicted by his group has now been experimentally observed and reported3 by researchers in China. Jingling Chen of Nankai University, one of the authors of that study, says their experiment, a first demonstration of two photons exchanging their spins without classically meeting each other, would help foster new research in the area of quantum information. The apparent separation of physical properties from quantum objects and the exchanges of these properties "lucidly exhibit the genuine quantum feature of the Cheshire cat".

Quantum physicist Eliahu Cohen from Israel's Bar-Ilan University says the HRI work has not only separated two photons from their polarizations, but also let them take each other's polarization. The conceptual implication could relate to the question of what inherently characterizes a particle. "....the practical implication would be to attempt to utilize the proposed effect in quantum communication and computation," he says.

References

1. Das, D. & Pati, A. K. Can two quantum Cheshire cats exchange grins? New J. Phys. 22, 063032 (2020) doi: 10.1088/1367-2630/ab8e5a

2. Aharonov, Y. et al. Quantum Cheshire cats. New J. Phys. 15, 113015 (2013) doi: 10.1088/1367-2630/15/11/113015

3. Liu, Z-H et al. Experimental exchange of grins between quantum Cheshire cats. Nat. Commun. 11, 3006 (2020) doi: 10.1038/s41467-020-16761-0
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