A healthy person who is infected by a pathogen and shows no symptoms of disease. People can become infected with a pathogen and experience no symptoms, but still transmit, or “carry” the pathogen to another person, infecting them. That person may then become sick, even if the original carrier does not. With COVID-19, it is hard to say just how many infectious people are asymptomatic; researchers give an enormous range of 14% to 50%. More likely, many people are pre-symptomatic because people who are infectious may take several days before they show symptoms such as headaches, congestion and fatigue, and the symptoms are so varied between people that not everyone is aware that they have symptoms of COVID-19.
