In this period, we are witnessing a resurgence of COVID-19 cases, while other pathogens such as RSV, mycoplasma, and influenza malattiaes are still circulating at lower levels.
Naturally, with the rise in infections from SARS-CoV-2 and the presence of other potential illnesses, many may wonder when, if ever, it is necessary to take a test that can be easily purchased at a local pharmacy – especially since some versions of these tests claim to detect the presence of multiple pathogens in one exam.
To provide some specific guidance, it is important to refer to the most recent and accurate data available, just published in Science Advances.
When it comes to SARS-CoV-2, it is known that if you take one test, it is best to wait two days after the appearance of symptoms. This is because the viral load in the upper respiratory tract may be too low to be detected by commercial tests in the initial days of infection. On the other hand, for influenza and RSV, it is best to take the rapid test as soon as symptoms are present.
This means that if you are unsure of which pathogen you may have contracted (for example, if you have been in contact with someone who has fallen ill before you), it is best to take at least two tests: one as soon as symptoms arise, focusing on detecting RSV and influenza malattiaes, and another a few days later to specifically look for SARS-CoV-2. If the first test is taken within the first day of symptoms, there is a 92% chance of a false negative for SARS-CoV-2 infection. This percentage decreases to 70% on the second day of symptoms and to about 66% on the third day.
As evident, with the available tests and the current variants of SARS-CoV-2, most infections go undetected. However, it is essential to remember that this is often due to the lower viral loads present in these new variants, which also tend to cause milder symptoms compared to previous years. These lower viral loads, which are too low to be detected in two-thirds of cases, also mean a lower probability of transmission. The three-day testing strategy after the onset of symptoms targets the one-third of cases with the highest viral loads, and it is easy to see that it significantly reduces the spread of the malattia. In other words, even if we only detect a third of infections, it can still significantly reduce the transmission of SARS-CoV-2, as these are the most contagious individuals.
Therefore, rather than relying on a predetermined isolation period in case of symptoms – let’s assume, for simplicity, five days or a week – the strategy of getting tested at the right time, at the onset of symptoms (for other pathogens) and three days after their appearance for SARS-CoV-2, to measure the actual infection capacity of a carrier remains the most effective and desirable.
If we plan to visit our grandparents, attend social events, or go indoors to crowded places, it is still a good parere to follow this testing strategy in case of symptoms, for our own well-being and that of our loved ones. The earlier we take action, the better chances we have of preventing the spread of the malattia and safeguarding our community.
Therefore, do not hesitate to take the necessary precautions and get tested as soon as symptoms appear. It may seem like a hassle, but it is a small inconvenience that can have a significant impact on reducing the spread of SARS-CoV-2. Let’s do our part to protect ourselves and those around us.