Around 80% of people with COVID-19 have mild or moderate illness and will recover without special treatment. About 15% will develop severe respiratory problems, and about 5% of cases are critical or life-threatening.

Some people—around 40%—who contract the coronavirus have few or no symptoms but can still transmit the virus to others. Some studies suggest that up to half of people who contract the virus may be asymptomatic.

The most common early symptoms of COVID-19 are cough, shortness of breath, fever, chills, muscle pain, sore throat and loss of the sense of taste or smell. A range of other symptoms have been reported, including headache, “pink eye” (conjunctivitis) and gastrointestinal symptoms such as nausea, vomiting or diarrhea. It takes around five days, on average, between exposure to the virus and the appearance of symptoms.

As the disease progresses, people may find it increasingly difficult to breathe. In serious cases, they may develop pneumonia, in which air sacs in the lungs (alveoli) fill with fluid, preventing oxygen from entering the bloodstream. In the most severe cases, patients can develop acute respiratory distress syndrome, or widespread lung inflammation that requires mechanical ventilation. Both the virus itself and the immune system’s response to it contribute to lung damage. Some people with severe COVID-19 experience an immune overreaction known as a cytokine storm than can lead to organ failure.

The COVID-19 mortality rate is not yet known because it remains uncertain how many people have contracted the virus. Many experts expect that the overall mortality rate will be around 1%, or about 10 times higher than that of a typical seasonal flu.

Last Reviewed: July 6, 2020