Generally speaking, vaccinated individuals should wait five days following exposure before undergoing an antigen test, though this time frame can vary. Millions of individuals are scared they may have been exposed to the Omicron variety and want to know if they are afflicted.
However, fast antigen tests at home can be hard to come by in some locations, and PCR tests can take days to deliver a result (assuming an appointment is even possible). Once you have access to a priceless test, when would be the greatest moment to use it to acquire the most reliable results?
According to Gigi Kwik Gronvall, an immunologist at the Johns Hopkins Bloomberg School of Public Health, the amount of virus in the body, also known as viral load, often peaks five to seven days after exposure to the original strain of SARS-CoV-2, the coronavirus that causes COVID.
The highest viral load will provide the best possibility of identifying the virus. Hence the CDC and many state health agencies advise exposed people who have been vaccinated to wait until this period before taking a test after coming into contact with someone who has COVID.
However, this is no longer the case with the Omicron form, as symptoms start showing up sooner after infection. This means sick people have a greater opportunity to infect others. Current CDC recommendations to isolate for five days after infection may not be long enough since newer studies reveal that patients infected with Omicron may continue to shed the virus for several days after the onset of symptoms.
Is there any correlation between the various forms of testing?
Customers can choose between two primary types of COVID testing, and their sensitivity varies greatly. It takes only 200 copies of SARS-CoV-2 to be detected in a 1-milliliter sample using a polymerase chain reaction (PCR) assay, which analyzes viral RNA in the body. By contrast, if fewer than 500,000 viral copies exist, a fast antigen test may not return positive.
Since the number of viral particles exhaled by a person does not necessarily correlate with the amount of virus reproducing in the body, it is not apparent if a higher viral load automatically suggests a person is more infectious.
Rapid antigen tests can not detect SARS-CoV-2 until peak viral load, but according to Gronvall, the assumption is that a positive test is a good indication of contagiousness. Due to its sensitivity, a PCR test may detect viral traces in the body long after the infected person is no longer infectious.
Ajay Sethi, an epidemiologist at the University of Wisconsin-Madison, says that it is getting harder at this time in the pandemic to tell whether or not one variety reaches a greater viral load or how that viral load interacts with infectiousness.
Various individuals’ immune systems will react differently to the newer variety because so many people have already been infected with COVID or received varying numbers of vaccination doses. Sethi argues that predicting which mutation will result in a more potent virus is too difficult.
Isolation and Precautions for People with COVID-19
The Centers for Disease Control and Prevention and many state health authorities recommend waiting five to seven days before treatment.
The recommendations are based on the typical latency period associated with the first SARS-CoV-2 strain: The likelihood of contagiousness is low if symptoms have not appeared after five days. The premise is that there will be enough virus for a PCR or quick antigen test to conclusively yield a positive or negative result while viral load and symptoms peak.
However, symptoms appear three days after exposure, on average, in the case of the Omicron variety. Evidence is also mounting that patients with Omicron can become infectious at least a day before their symptoms manifest.
Research published as a preprint on medRxiv on January 5 indicated that 30 patients monitored during an Omicron outbreak were infected for days before quick antigen tests detected COVID.
According to a recent study from Japan, some individuals with the Omicron type may not achieve peak viral load until three to six days after the onset of symptoms. Omai Garner, a clinical microbiologist at the University of California Los Angeles Health System, adds that this does not mean people are not infected much earlier.
Due to their ability to detect infections before viral load peaks, PCR testing may be superior for detecting Omicron shortly after infection but before transmission. However, it may take several days for PCR testing to yield findings, by which time the infected person may have already spread the disease to others.
Why should we wait to get tested if Omicron carriers become contagious two days after exposure?
Two days following exposure, testing poses no risk. A quick antigen test may not be able to pick up the virus on day 2. Thus a negative result may give a false sense of security.
A negative test one or two days after exposure, especially a quick antigen test, is meaningless, and the subject should retest before being released from isolation.
To sum up, when should a person get tested for COVID?
Even if you are not yet contagious, a PCR test on day three can tell you if you have the virus.
It all depends on the situation if you don’t have access to PCR tests and only have one antigen test available.
Sethi and Garner believe that waiting five days after exposure to do an antigen test is the safest way to determine whether or not your symptoms are due to COVID, provided you have the opportunity to remain isolated and know exactly when you were exposed.
Rapid antigen testing for two days could be useful if you have no symptoms, work in a social environment, and only have access to a single test.
Sethi says you can assume you have COVID if the test comes up positive. He says you’ll be glad you had another test if this one turns out to be negative.
However, until a sufficient amount of time has gone after the test, it is recommended that you treat the condition as if you have COVID. The results of any test, especially a fast antigen test, cannot rule out the possibility of infection or future infection. For more information visit our website.
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