Confusion between these two diseases is very common, despite the fact that they are different pathologies. The main difference is that they are caused by different types of viruses.
The flu is caused by a single virus, the influenza virus, while the cold is caused by many others, such as rhinovirus, parainfluenza and respiratory syncytial virus (RSV).
Because of this greater variety of causative viruses, it is much more common to get a cold than to catch the flu.
The symptoms in the two diseases are very similar, but usually, in the cold, they are milder. What differentiates them most, in relation to physical signs, is the presence of fever , being uncommon or milder in the cold.
When fever is a symptom present in the cold, it is much less severe than in the flu. Both conditions can cause sore throat , runny nose and malaise. However, despite the discomfort, the cold usually does not prevent the person from performing their daily tasks.
This point is considered important in differentiating the two diseases. The flu is capable of making the patient much more debilitated, as it causes high fever, muscle inflammation and a great indisposition.
Thus, if what the patient is feeling leaves him unable to go to work, study or do any activity, it is more likely to be the flu and not a cold.
In addition to being confused with a cold, it is common for people to confuse the flu with allergic rhinitis, a disease that also causes irritation in the throat, nasal congestion, sneezing and runny nose.
However, in spite of “passing” through the flu, allergic rhinitis is not transmissible, but a chronic disease.
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