The specific set of symptoms COVID-19 patients experience at the onset of the disease may predict how severe their case will become, according to a study by researchers at King’s College London. The study identified six “symptom clusters” of COVID-19 disease, which are listed below in ascending order of severity:
- Type 1, “flu-like with no fever”: headache, loss of smell, muscle pain, cough, sore throat and chest pain.
- Type 2, “flu-like with fever”: fever and loss of appetite in addition to headache, loss of smell, cough, sore throat, and hoarseness.
- Type 3, “gastrointestinal”: diarrhea and loss of appetite, no cough, headache, loss of smell, sore throat, and chest pain.
- Type 4, “severe level one, fatigue”: fatigue in addition to headache, loss of smell, cough, fever, hoarseness, and chest pain
- Type 5, “severe level two, confusion”: confusion in addition to headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, and muscle pain.
- Type 6, “severe level three, abdominal and respiratory”: shortness of breath, diarrhea and abdominal pain in addition to headache, loss of smell, loss of appetite, cough, fever, hoarseness, sore throat, chest pain, fatigue, confusion, and muscle pain.
These six COVID-19 types help clarify what has been a confusing disease. It is like six different types of flu that require different kinds of treatment. Up to now, they were either not fully recognized as being COVID-19 disease, or treated as a single disease. Clearly, different people have different responses to the coronavirus. It also is possible that virus variants might lead to the different clusters of symptoms, but, at this point, we are not certain of that. What is important is that as we learn how the disease manifests itself, we learn how to better diagnose and treat it, which should bring mortality, and, hopefully, morbidity rates down.
The study referred to above was done using a symptom self-reporting app called ZOE COVID Symptom Study app, which asks users to log health information and potential COVID-19 symptoms daily. The study analyzed data from 1,600 app users in the U.S. and U.K. with confirmed COVID-19 cases and who logged their symptoms during March and April. This showed that 20% of people with type 6, and 10% of people with type 5 symptom clusters eventually required breathing support, compared to just 1.5% of people with type 1.
The 5 and 6 symptom types signaled a “high risk” for needing hospitalization, and almost half of type 6 COVID-19 patients were hospitalized. In just five days, the app was able to identify which symptom cluster the patient belonged to— which is eight days earlier than when most people who need breathing support go to a hospital. The study also found that people in types 4, 5 and 6 clusters were older, more likely to be overweight and more likely to have preexisting conditions than those in symptom cluster types 1, 2 and 3. Therefore, the app seems to be a useful diagnostic tool for a complicated disease.
Finally, the app showed that a cluster of nonspecific symptoms not previously associated with COVID-19, such as headache, sore throat and muscle pain, without fever and loss of smell, can detect potential COVID-19 cases before the classic symptoms of fever, shortness of breath, loss of smell, etc. set in. Such early symptom awareness can limit virus spread to colleagues, friends, and family. So, using this app to detect symptom clusters promises to not only provide more focused and timely therapy, it can also help limit the spread of the disease from people who have not been diagnosed with COVID-19, which has made this disease especially vexing to control.
This is a wholly new disease, which we are learning about on the fly. As we learn more about it, we improve our ability to diagnose, treat, and ultimately prevent it. This study takes us one step closer to that goal.