Between the cold, the flu and the covid-19, the cold is the mildest disease. Its most characteristic symptoms are the appearance of nasal congestion and this feeling of being feverish, but without the thermometer rising, or at least not rising very high. And above all it causes cough with sputum, that cough that we could call wet. In short, its symptoms are the ones we all know: the most common are nasal congestion, watery eyes and, sometimes, sore throat. We could say in some way that there is no cold without a runny nose. This disease is mild, usually heals alone in two or three days, also because there is no treatment to cure it, just to alleviate the symptoms. Many colds are caused by a coronavirus, but not by what causes covid-19, called SARS-Cov-2, but by other viruses of the same family that were already known before the cause of the pandemic appeared. For some time, at the beginning of the epidemic, it was thought for this reason that it was possible that some people – especially children, more prone to colds – had antibodies against SARS-Cov-2. Then it was proved that it is not so.
As for flu and covid-19, they are more difficult to distinguish, because the symptoms are very similar. Both have or may have a dry cough, both cause high fever and general malaise. The only important difference is that in covid-19 anosmia is very common (absence of smell). Even many mild covid-19 patients have this loss of smell as their only symptom. Feeling tired, covid-19 is also much more frequent, an extreme fatigue reported by many patients. Generalized muscle pain is more common in the flu. But, otherwise, the symptoms are very similar. Another difference may be that the flu starts more suddenly, while covid-19 tends to appear more slowly. In it the person gets infected and one day he is a little bad, the next day a little worse, the next day even worse, and then it is when the high fever and the feeling of tiredness appear. And it is usually accompanied by the aforementioned loss of smell. In the flu, everything is much more sudden – you wake up one day and realize: “I am terrible, everything hurts”. Both can cause diarrhea. Vomiting is unusual, but both diseases can cause nausea.
They are so similar that even for doctors at health posts it is very difficult to distinguish one from the other. The only safe way is to use a diagnostic test: one of fast antigens or a PCR that detects if what the person has is covid-19.
If you have symptoms and are unsure whether it is flu or covid-19, the first thing to do is to observe the evolution. If you feel unwell and then start with a strong cough, fever and feeling tired, it is best to seek medical attention and order an examination to confirm or rule out the coronavirus.
It is also very important to prevent it. We must not forget the hygiene rules we followed when the pandemic started. In the first wave, we all asked and tried to follow the recommendations. Now we seem to have forgotten them, but they are still just as important. If you go out on the street, you must do a number of things when you return home: for example, disinfect the shopping cart wheels; leave the shoes off; wash your hands (this is very important to do) and wash your clothes, especially children’s clothes. And the good thing about these hygiene rules is that, in addition to protecting us from covid-19, they also protect us from the flu.
And, moreover, let us not forget the convenience of being vaccinated against the flu, especially if we are in a risk group: over 60, diabetic, hypertensive, cardiac or cancer patients, as well as children and pregnant women in the second trimester of gestation.
Maria Elisa Calle she is a full professor at the Faculty of Medicine of the Complutense University of Madrid, specializing in epidemiology and preventive medicine.
Question sent by email by P. Fernández to the section They Respond, a weekly scientific office sponsored by the Dr. Antoni Esteve Foundation and the L’Oréal-Unesco program ‘For Women in Science’, which answers readers’ questions about science and technology. The doubts are answered by scientists and technologists who are members of AMIT (Association of Women Researchers and Technologists).
Coordination and writing: Vitória Toro
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