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None coronavirus variant such as Omicron it spreads so quickly and has circumvented the shield of vaccines like this one. The new version of the virus is also testing antigen tests, which are the mainstay of containment strategy in the sixth wave. It was already known that the self-tests were not infallible against Covid. And that its effectiveness changes according to the commercial brand. If the result is positive, the certainty of the diagnosis is almost one hundred percent, but it is not as reliable when the result is negative.
The first studies in real life reveal that symptoms appear before the test is positive. That means that if someone has been in contact with someone infected, they begin to have symptoms (cough, sore throat, muscle discomfort …) and their negative test should not be trusted.
Most likely, you are infected and need to be isolated to avoid infecting other people. The next step is to repeat the test one or two days later and check if the positive has emerged.
In any case, antigen tests are highly specific, comparable to PCR in detecting infection in the first week after infection. In the nasopharynx, the highest viral load is observed above all in the first 5 to 7 days and then decreases until its disappearance. False positives in antigen tests are more frequent in massive screenings in populations with a low prevalence of infection. They can also be due to sample contamination.
It is also possible to obtain in them false negatives, since this type of tests have a lower sensitivity than PCR and their efficacy is reduced if the viral load is low, which occurs during the initial or final days of the infection. Those with a low viral load or asymptomatic may be more likely to get a false negative.
However, the doubts surrounding these tests are such that Germany has announced an investigation to determine if they are so effective in detecting the Omicron variant as they were when the dominant version was the Delta. The high rate of reinfections, which is not reflected in the evolution of the positive tests, has sown certain doubts in the German authorities and among consumers, for which the Minister of Health, the Social Democrat Karl Lauterbach, has recognized that «we don’t know exactly how well they work these tests for Ómicron ‘and commissioned a study. Specifically, Lauterbach has asked the Paul Ehrlich Institute to develop a list of rapid coronavirus tests that are particularly reliable for infections with the Omicron variant, providing “evidence that they are particularly suitable for Omicron or to detect it early.
If an antigen test is positive, it is no longer mandatory to confirm it by PCR, although it depends on the situation. The results of the self-tests, in situations in which the autonomous communities cannot guarantee the confirmation in time by PDIA, and that, therefore, are handled as Covid cases, will be considered confirmed, will be integrated into the surveillance system and in the usual notification through SIVIES to the Ministry of Health, according to the
Document on Adaptation of the Covid-19 Early Detection, Surveillance and Control Strategy in a period of high community transmission, updated on December 30.
On the other hand, even if a person has received all three doses of the vaccine, they can catch it and spread it to others. However, although PCRs can test positive for days or even weeks, that does not necessarily mean that they are still infectious.
Adapt Insulations
In the US, the isolation period was shortened to five days for people who have no symptoms or whose symptoms are decreasing, although they must still wear a mask with other people for an additional five days. The United Kingdom Health Security Agency (UKHSA) says it has no plans to do the same and that the situation in the two countries is different, an option to which Prime Minister Boris Johnson has left the door open. In Spain, on the other hand, isolation is 7 days.
According to UK health authorities, it is estimated that between 10 and 30 per cent of people remain positive on day 6, and that 5% will remain positive on day 10, although the guide says they no longer it is necessary to isolate on the 11th.
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