4/30/2023 0 Comments False negative pregnancy test![]() ![]() SARS-CoV-2 tends to infect cells lining the airways, often striking those in the nose first. Similar factors may also influence when individuals start to test positive for the virus, using diagnostic tests such as PCR or lateral flow tests. The precise timing of these events is influenced by the rate at which the virus replicates once it has infected cells, and whether these cells are implicated in transmitting the virus to other people - as well as how much virus the person was initially exposed to, how they were exposed, their biological susceptibility to that type of virus and their immune response. Less sensitive lateral flow or rapid-antigen tests require a higher viral load to record a positive result, which is why they often only identify people during their most infectious period. The average incubation period for COVID-19 is 5-6 days (although it can be up to 14 days), and researchers estimate that people become infectious 2-3 days before they develop symptoms. This is what makes COVID-19 so difficult to contain – the most successful intervention (quarantine) is often implemented too late, as people are unaware that they are infectious due to a delay in symptom onset. For instance, people infected with Ebola develop symptoms before they become infectious, whereas with COVID-19, they usually become infectious before they develop symptoms – and many people never develop symptoms at all. The degree to which they overlap depends on the virus. There is also a period known as the “incubation period” before they develop symptoms. Why?Īt the beginning of any viral infection, including COVID-19, there is a period of time called the “latent period” when a person is infected, but is unable to transmit the virus to anyone else. Yet, if you were to do a PCR test at this stage, you would most likely test negative. As they breathe out and you breathe in, some of their viral particles become attached to cells lining your nose and upper airways, and begin to gain entry. ![]() You sit next to someone who is infected with coronavirus. ![]()
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