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Differential diagnosis of influenza
Last reviewed: 03.07.2025
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The correct diagnosis of flu determines how quickly you will recover and whether there will be complications affecting all vital organs. Differential diagnostics of flu is carried out for this purpose. The doctor's task is to distinguish flu from other diseases that can affect the upper respiratory tract. For example, flu can be accompanied by adenovirus infection, parainfluenza, respiratory sensitization disease, mycoplasma and other pathogens that can easily deprive a person of working capacity and good mood.
[ Early diagnosis of influenza and the success of its treatment
These two components directly depend on each other. Correct diagnostics of flu, which should be carried out as early as possible, allows the doctor to prescribe an anti-epidemic regimen for the patient, as well as determine the correct strategy for treating this insidious disease.
The most important feature that distinguishes flu from other respiratory diseases is the signs of severe intoxication of the body. That is, headaches and muscle pain, confusion, high fever (although flu can pass without it) and vomiting (sometimes). With other colds or infectious diseases, toxicosis manifests itself quite weakly, even if a person has a very high temperature. And if it is an infection of the nasal sinuses (rhinovirus), then toxicosis may not manifest itself at all.
How to diagnose flu by its external manifestations?
Did you know that a doctor can diagnose the flu based on the signs of other, concomitant diseases? For example, tonsillitis and pharyngitis appear when the body is affected by adenovirus, doctors diagnose laryngitis mainly during parainfluenza, and if laryngitis appears together with tracheitis, this may mean a severe attack of the common flu.
If a patient is diagnosed with rhinitis, it means that he also has an acute respiratory viral infection. But the nature of the acute respiratory viral infection – more intense or weaker – may indicate different concomitant diseases. For example, doctors diagnose moderate rhinitis when the body is affected by the common flu, and rhinitis with swelling of the sinuses and difficulty breathing indicates parainfluenza, especially if these symptoms are accompanied by the release of serous mucus.
Flu and adenovirus
If a person suffers from an adenovirus disease, then rhinitis with very significant swelling of the nasal conchae is added to it. The mucous membrane of the nose is very swollen, the nose is stuffy, but the discharge from it is still abundant. At the same time, among the external signs of adenovirus infection, conjunctivitis is also observed (usually occurring only on one side of the face), as well as enlarged lymph nodes.
Additional tests also show liver and spleen dysfunction (though not in all cases). The heart may also not work very well – heart failure may manifest itself. It is not always visible externally, by any signs, but an electrocardiogram usually clearly shows changes in the heart rhythm. Therefore, if the doctor doubts the nature of your disease, he will prescribe an electrocardiogram.
The doctor may also prescribe blood and urine tests. But the main method of differential diagnosis of influenza, of course, is an external examination, careful questioning of the patient, measuring temperature and blood pressure, and listening to the chest.
How to diagnose complications of influenza?
Usually, high temperature during flu lasts no more than 4-5 days. But if it does not go away on the fifth day, it means that the person probably has complications and needs a more thorough diagnosis. Then the doctor additionally checks the functioning of the kidneys, liver, respiratory system, as well as the liver and brain.
A dry or wet cough and difficulty breathing indicate problems with the respiratory system and the addition of bronchitis. In such cases, the doctor additionally prescribes an X-ray. With changes in the bronchi, swelling and a cellular structure are clearly visible on the X-ray. This may indicate a bronchial exacerbation.
If the X-ray clearly shows changes in the vessels, a very clear pattern and rare or frequent foci of interstitial changes, this may indicate that the infection is mycoplasma. To make sure that it is mycoplasma, you need to monitor its characteristic symptoms. You should know that mycoplasma infection that causes flu does not manifest itself suddenly, but gradually, while the temperature may be high, but there may be no signs of intoxication in the form of muscle pain and headache.
So, when a person is affected by the flu, it is very important that the flu diagnosis is made in time. This will allow the disease to proceed less severely and for a shorter period of time, and also reduce the likelihood of side effects.