午夜福利1000集合

HAVE we been getting covid-19 all wrong? As the list of symptoms recognised by health authorities evolves, we are starting to learn that people seem to fall into one of several symptom clusters, and that we might be missing the most important signs of the disease in children.

The findings could help researchers better understand how the virus affects individuals differently, and how an outbreak in a preschool might look very different to one in a care home.

In January, when the world was first alerted to a new coronavirus spreading in the Chinese city of Wuhan, health authorities listed cough, fever and difficulty breathing as key symptoms. People with severe infections developed pneumonia. The illness looked like many other respiratory infections.

With time, that picture evolved and today, both the and the list a plethora of symptoms for covid-19.

鈥淥ur understanding of the symptoms is changing all the time,鈥� says Angela Rasmussen at Columbia University Mailman School of Public 午夜福利1000集合. 鈥淎t the start, we focused on respiratory symptoms because it鈥檚 a respiratory disease, but we鈥檝e learned since that it鈥檚 much more complex than that.鈥�

One of the first discoveries was that the virus seems to trigger more severe symptoms in older people, as well as in those with underlying health conditions. But the effect on any individual can vary hugely 鈥� many young people have died, too. 鈥淲e realised it could be very different from one person to another,鈥� says Carole Sudre at King鈥檚 College London.

It鈥檚 not clear exactly what determines how ill a person might get, but there are plenty of factors that could play a role. 鈥淎ll of these people are from different places, they have different diets, genomes and epigenomes, they have different medical statuses and access to healthcare,鈥� says Rasmussen. 鈥淎ll of those things are going to create a unique environment for the virus to replicate and for unique bodies to respond in different ways.鈥�

The way individuals are exposed to the virus could also have an effect, says Rasmussen. Subtly different variants could trigger different immune responses, for example. The amount of virus a person is exposed to might influence which symptoms they develop, too, as could the route of infection, for instance whether by nose, eyes or mouth.

One attempt to understand how the virus affects people in different ways is based on data from the , developed by health science company Zoe. Since its launch at the end of March, more than 4.4 million people have signed up across the UK, US and Sweden. App users enter their age, location and health information, and are then asked to report how they feel each day. People can also log any coronavirus tests they have taken.

Based on a sample of 1653 app users, the team behind the app has (see 鈥�Six types of covid-19?鈥�).

鈥�4.4 m
The number of people using the Covid Symptom Study app鈥�

Three of the clusters are relatively mild. People who fall into the more severe clusters tend to develop fatigue, chest pain and confusion. Those who fall into cluster six often become very unwell (medRxiv, ).

鈥淚f only the upper respiratory system is affected, then the risk of going on to need hospital and breathing support is much less,鈥� says Claire Steves at King鈥檚 College London, who co-authored the study. 鈥淲hen鈥� a person gets symptoms all over their body 鈥� not just nose and throat, but also muscles, chest, tummy and brain 鈥� that鈥檚 when they are more likely to need hospital support.鈥�

Personal predictions

Sudre, who is also on the study team, hopes that recognising a person鈥檚 symptoms in this way might help health professionals predict the level of care someone could need.

The findings could also help inform who gets a test for the coronavirus. In the UK, for example, the government currently advises that only those with fever, a persistent cough or a loss of taste or smell get tested. Given the variability of symptoms 鈥� and that many people won鈥檛 have any at all 鈥� these criteria will undoubtedly miss cases.

Researchers are also trying to figure out how symptoms develop over time. Typically, the symptoms listed by the UK government tend to appear anywhere between two and 14 days after infection. 鈥淚t could be too late, and you may have already infected people,鈥� says Sudre. Her colleagues are investigating which symptoms are most likely to develop first. So far, it appears that earliest 鈥� which might also be symptoms we easily dismiss.

Children seem to be affected differently, and another set of symptoms might be more appropriate for spotting covid-19 in them. Young children in particular seem to experience an infection very differently to adults.

That鈥檚 what Tom Waterfield at Queen鈥檚 University Belfast and his colleagues found when they assessed the symptoms of illnesses across the UK. Sixty-eight were confirmed to have had the coronavirus. Waterfield鈥檚 team compared their symptoms with those of children who hadn鈥檛 had the virus.

鈥淥ur study is showing a big range of symptoms with lots of overlap,鈥� says Waterfield. His team used a computer model to work out which were most predictive of covid-19, rather than of other common infections. While many of the children had a fever or a cough, for example, these symptoms were also linked to other viruses. 鈥淚f you want a symptom that could give you a high pickup with the least number of extra tests, it would be diarrhoea and vomiting,鈥� he says.

The current UK testing strategy would have missed 24 per cent of symptomatic children, the team found, but including diarrhoea and vomiting in testing criteria would mean that 97 per cent would have been detected (medRxiv, ).

The key symptoms in younger children also seem to look different to those seen in older children. Teenagers are much more likely to report changes in their senses of taste and smell than young children, although young children might simply struggle to express the problem.

This fits with other research suggesting that the way the virus spreads in teenagers is closer to that in adults, but we still don鈥檛 know why this might be the case.

鈥淚t might have to do with differences in the immune system between young and old,鈥� says Petter Brodin at the Karolinska Institute in Stockholm, Sweden. Some researchers think it may be related to ACE2 receptors, which the virus binds to. Children may express fewer of these receptors in their noses and throats.

鈥淚f you want a symptom that will give the highest pickup with fewest tests, it is diarrhoea and vomiting鈥�

It also suggests that the coronavirus is spreading in a different way among young children. While it is largely thought to spread via large droplets and smaller aerosols in the air, the prevalence of diarrhoea and vomiting in young children suggests that poor bathroom hygiene might play more of a role for them, says Waterfield.

Fatigue was another common symptom among the children in Waterfield鈥檚 study, and he worries that many will continue to experience this after they have recovered from the initial infection. This has become a trend in many adults, who describe experiencing symptoms of 鈥�long covid鈥� for weeks or months after they first became unwell.

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