Covid: why do I have symptoms but the test is negative?

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Many ask themselves the question during this new wave of Covid: why do I have all the symptoms compatible with the coronavirus but the test comes out negative? In recent weeks, the idea has begun to circulate that the tests no longer work correctly with the new variants in circulation, in particular with Omicron 5, which represents 75.5% of infections in Italy. Many of those who decide to repeat the test begin to test positive when the symptoms have already disappeared.

The reported “time lapse” has drawn the attention of the scientific community and the Italian College of Physicians has wanted to analyze the problem looking for an explanation. It is not easy to estimate how widespread the phenomenon is and which people are most at risk because fewer and fewer people are turning to laboratory tests.

The behavior of our immune system

However, it is also difficult to understand the cause. The most widespread hypothesis is linked to the behavior of our immune system: it is thought that the symptoms precede the positive result of the test because today the immune system is activated much faster against the virus. The appearance of the first symptoms would be a consequence of the activation of the immune system that fights the infection.

At the beginning of the pandemic, in fact, infections occurred among people who had never suffered before. coronaviruswho were not vaccinated, and the virus could act undisturbed for several days before the immune system could detect the infection.

Today, however, with the majority of the population vaccinated or already exposed to the virus, the immune reaction is faster and can lead to cases in which symptoms appear but are not positive, because the viral load is still not sufficient. compared to the sensitivity of the test.

The dynamics of some variants

Another hypothesis refers to the different dynamics with which the most recent variants circulate in the body. Some studies, in fact, have found a lower accumulation of viral particles of the new variants in the cells of the nose, which makes false negatives more likely because during the sampling, not enough is collected to give a positive result in the Test.

Other studies have also found that omicron it can, in some people, be detected in the mouth or throat before it is in the nasal passages. Furthermore, given the generic nature of the symptoms, it cannot be excluded that the manifestations are actually due to something else.

The execution of the test

A third possibility is that the delay is a reflection of how the way nasal swabbing is performed has changed over time. The greater use of home tests, in fact, can affect the quality of the result: many people do not collect the biological material in the nose with special care or in great depth, which results in a higher frequency of false negatives.

Precautions even with negative test

There’s no need to worry for now, but it can help to take a few precautions. “If you start having symptoms, assume you’re contagious,” he explains. Yonatan Gradwho studies the coronavirus on the Harvard School of Public Health.

“People forget that as soon as symptoms develop, you have to behave differently. A negative test in the presence of symptoms should not be a pass to get out,” he confirms. Emily Martinepidemiologist expert in infectious diseases of the University of Michigan. And this is true in the presence of all kinds of viruses, not just the coronavirus.