Final answer:
A person is infectious when they can transmit a disease to others. The duration of infectivity varies depending on the disease, and it is possible to be infectious even without symptoms. Following public health guidelines is important to prevent the spread of infectious diseases.
Step-by-step explanation:
A person is infectious when they are able to transmit a disease to others. The specific duration of infectivity depends on the disease. For example, with the common cold, a person is typically infectious for several days to a week after symptom onset. With COVID-19, individuals are considered infectious for a period of time that typically begins a couple of days before symptoms appear and lasts until they are no longer contagious, which is usually around 10 days after symptom onset.
It is important to note that a person may be infectious even if they do not have symptoms. This is called asymptomatic transmission. For some diseases, the infectious period may extend beyond the resolution of symptoms, posing a risk to others. It is crucial to follow public health guidelines, such as wearing masks, practicing good hand hygiene, and maintaining physical distance, to prevent the spread of infectious diseases.
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