Truly asymptomatic COVID-19 patients (as distinguished from pre-symptomatic patients) have been described, but their proportion is not well characterised yet.
Among symptomatic patients in China, 81% developed mild disease, an estimated 14% developed severe disease (with hypoxaemia, marked tachypnoea and extensive lung infiltrates), while 5% became critically ill (with respiratory failure, septic shock and/or multiorgan dysfunction).
Because of the strong effect of age on disease severity, the proportions of mild, severe, and critical cases seen in a country will partially depend on that country’s population age structure however.
The most common presenting symptom has been fever in approximately 90%, but importantly this may only be present in a minority of patients on admission. A cough is present in two-thirds of patients, but sputum production is only reported by one third of patients, as is dyspnoea. Myalgia, a sore throat, nausea, vomiting, and diarrhoea are all present in less than one fifth of cases.
Anosmia (loss of sense of smell) and dysgeusia (alteration of the sense of taste) have also emerged as relatively common, early, and moderately specific symptoms.
Abnormalities are visible on chest X-ray in at least 60% of hospitalised COVID-19 patients, with chest CT scans being more sensitive. These are typically bilateral patchy ground glass opacities, though other patterns have been described.
However, a normal chest X-ray or chest CT scan does not rule out COVID-19. This is especially true of patients with mild disease, in whom a majority of chest X-rays may be normal.
The CDC has an updated listed of clinical symptoms associated with COVID-19:
Fever or chills
Shortness of breath or difficulty breathing
Muscle or body aches
New loss of taste or smell
Congestion or runny nose ***NEW***
Nausea or vomiting ***NEW***
There are also several skin presentations associated with COVID-19:
Answers extracted from: Clinical management of suspected or confirmed COVID-19 disease (Version 4, May 2020)