British scientists analysing data from a widely-used Covid-19 symptom-tracking app have found there are six distinct types of the disease, each distinguished by a cluster of symptoms.
A King's College London team found that the six types also correlated with levels of severity of infection, and with the likelihood of a patient needing help with breathing - such as oxygen or ventilator treatment - if they are hospitalised.
The findings could help doctors to predict which Covid-19 patients are most at risk and likely to need hospital care in future waves of the epidemic.
"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," said Claire Steves, a doctor who co-led the study.
Besides cough, fever and loss of smell - often highlighted as three key symptoms of Covid-19 - the app data showed others including headaches, muscle pains, fatigue, diarrhoea, confusion, loss of appetite and shortness of breath.
The outcomes also varied significantly; some got mild, flu-like symptoms or a rash and others suffered acute symptoms or died.
The study, released online on Friday but not peer-reviewed by independent scientists, described the six Covid-19 types as:
1 'Flu-like' with no fever: Headache, loss of smell, muscle pains, cough, sore throat, chest pain, no fever.
2 'Flu-like' with fever: Headache, loss of smell, cough, sore throat, hoarseness, fever, loss of appetite.
3 Gastrointestinal: Headache, loss of smell, loss of appetite, diarrhoea, sore throat, chest pain, no cough.
4 Severe level one, fatigue: Headache, loss of smell, cough, fever, hoarseness, chest pain, fatigue.
5 Severe level two, confusion: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain.
6 Severe level three, abdominal and respiratory: Headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, muscle pain, shortness of breath, diarrhoea, abdominal pain.
Patients with level 4,5 and 6 types were more likely to be admitted to hospital and more likely to need respiratory support, the researchers said.