Transmission and symptoms
Transmission of SARS-CoV-2 is mediated mainly via respiratory droplets from an infected person (20, 21 ). Of note, SARS-CoV-2 positive patients emit respiratory droplets in high numbers during speaking, which remain in the air up to 8-14 minutes (22 ). The average incubation time until the onset of COVID-19 is 4-11 days (23 ). The immune responses resulting from SARS-CoV-2 infection vary broadly and range from asymptomatic courses, over mild, moderate to severe courses with a need for hospitalization and intensive care. Typical symptoms of COVID-19 include dry cough, fever, myalgia, headache, anosmia and ageusia (24 ). Depending on the severity of the disease, even other organ systems such as the gastrointestinal tract, the liver, the renal system as well as the cardiac system might be involved and become symptomatic as well (Fig. 3).