How to distinguish between Covid-19, cold and flu?

The symptoms are mostly superimposable, if some nuances are excluded. This is why the role of prevention is always fundamental

(photo: Markus Spiske / Unsplash) So similar, so different. Covid-19 and flu do look alike, but it was immediately clear that the Sars-Cov-2 infection was not just a flu (in itself not to be underestimated). But it is undeniable that there are meeting points: both viral diseases, both respiratory, can above all lead to similar symptoms. Reason why, now on the eve of October, this year the advice to get vaccinated against the flu is stronger than usual. It could help the diagnosis and relieve, at least a little, the health facilities from the burden they face every year due to the flu. The role of the vaccine in differential diagnosis is supported precisely by the fact that many of the symptoms are similar between the two conditions. And if it is true that for both of them today the last word can only belong to the swab, some differences exist, although interpreting their meaning for diagnostic purposes remains the responsibility of doctors.

Flu, Covid-19 and colds

Fever, dry cough and fatigue. According to reports from the World Health Organization (WHO), these are the most common symptoms of coronavirus infection. But chills, body aches, headache, sore throat, diarrhea, nasal congestion, vomiting, diarrhea can also occur. However, all the same symptoms are also common in case of flu. More typical, but certainly not exclusive, of Covid-19 are the loss of taste and smell, shortness of breath and difficulty in breathing, but conjunctivitis and some skin manifestations, such as rashes and chilblains, have been associated with coronavirus infections.

In the case of colds, symptoms are generally limited to the nose and throat, with sore throat, congested nose, cough, loss of sensitivity in perceiving tastes and smells, sneezing. Compared to the flu, however, the symptoms are less strong and tend to have a gradual onset, and not as rapid as flu viruses.

The onset of symptoms

These symptoms tend to appear gradually, and although they are practically superimposable to those of the flu, some researchers have tried to understand if there are characteristics also in their appearance, which may perhaps be partly helpful in identifying suspicious cases. Last month, in this regard, a study showed for example that it was possible to identify a more frequent order in the onset of symptoms from Covid-19, which sees in succession fever, cough, muscle aches, nausea, vomiting and diarrhea. On the other hand, it is not infrequently the cough that appears first in the flu.

But more generally, the Americans agree with the CDC and the WHO, the appearance of symptoms from Covid-19 is different from that of influence in terms of absolute timing. That is: Sars-Cov-2 infections can have longer incubation times than those of influenza. Again in general, of course. In fact, if the average time of onset of symptoms from infection with a flu virus ranges from one day to 4 days, for Sars-Cov-2 we speak of an average of five days, although the window can widen from 2 to 14 days.

Cold, flu or Covid-19?

With the start of the next flu season, the circulation of parainfluenza viruses, and while we are still in full Covid-19 pandemic, understand, at least at first when the symptoms appear, what they refer to is not easy. But this is a task that is still relegated to the medical profession, Rocco Russo, pediatrician responsible for the technical table on vaccinations of the Italian Society of Pediatrics, reiterates: "With the opening of schools we know that we will find ourselves experiencing the pandemic emergency in a winter period in which there will be a greater circulation of other viral forms, in any case also we pediatricians operating on the national territory have at our disposal a series of specific ministerial recommendations, which following appropriate reports from parents will allow us to put implement all the procedures for the management of children with suspected Covid-19 symptoms ". What Russo refers to is the fact that parents will inevitably report symptoms referable to colds, flu and Covid-19, but that the mere presence of the symptoms cannot be, every time, a source of alarm: "The parent must intercept these symptoms and refer them to the pediatrician, who has the task of filtering the available information and understanding whether to treat the child as a suspected case or not ".

And doing so, continues the doctor, means first of all taking into account that the diseases infectious can occur in a nonspecific way with respect to the classical symptomatology and that the symptomatology differs from subject to subject. "We know that, in the case of Covid-19, the most frequent element is fever, together with the involvement of the airways with cough and sore throat - continues Russo - and that in general the clinical manifestations are more nuanced than in adults . And even if, for example, gastrointestinal symptoms such as diarrhea in children appear slightly more frequent than the flu, it is not possible to identify the different conditions on the basis of the symptoms alone ". Also because, continues the expert, influenza viruses change from year to year and from time to time the interest in the different parts of the body and therefore the manifestations, such as the gastrointestinal ones, may also change.

"Again today the first fundamental element in suspecting a Covid-19 case is contact with a positive ", remarks Russo, recalling the essential role of the recommended prevention measures against the spread of the Sars-Cov-2 virus:" Use of masks, personal distancing and frequent hand washing, prove to be valid preventive interventions not only against Sars-Cov-2 but also against the spread of other viruses, including influenza, for some of which we have the possibility of having a specific vaccine ", concludes the pediatrician," but we must not forget the behaviors: sending a child to school with a runny nose was wrong before and it is still wrong today ".