Sometimes, the diagnosis can be less straightforward for a number of reasons.
First, the clinical features of a common cold may coincide with those of pharyngitis and bronchitis, which are related syndromes of shared viral origin.
To complicate matters, pharyngitis and sinusitis can also be caused by bacterial infections.

Second, allergic diseases of the upper respiratory tract often have clinical features that resemble those of common colds.

Third, infants and young children are unable to express their symptoms, and doctors are challenged to distinguish between benign viral infections and serious invasive bacterial infections.

It can also happen that several diseases occur at the same time, making it difficult to separate the symptoms.

The definitions of the common cold are quite vague, but colds have the following characteristics:

• Feeling mildly uneasy (“unwell”)
• A chilling sensation (meaning feeling cold when the core temperature is normal or even elevated)
• Sneezing (excessive nasal discharge above the normal physiological level)

These would be the main symptoms that people experience.
Perhaps the chills that people feel (a kind of hypersensitivity to room temperature) are the reason why the illness is called a cold.

Everyone has had a cold at some point, so it’s not hard to recognize the symptoms.
However, there are many variations on the theme.

The infection usually starts in the lining of the nasal cavity (the typical common cold), but it could start in the throat, sinuses, ears, or bronchial tubes, in which case the first symptom could be a sore throat, pain in the face, bones, ear pain, or cough.
Soon after, with the advent of the runny nose that accompanies the general feeling of coldness, we realize that the constellation of symptoms is a cold.

The common cold is caused by a wide variety of viruses.
Most of which are rhinoviruses and benign forms of coronavirus.

It is often difficult to distinguish when there is discomfort or sore throat if this is a viral or bacterial symptom.

Many people faced with a symptom of this type believe that they should take an antibiotic, but the ideal before making a decision about it would be to have a Streptotest.

This is a rapid throat test that can be purchased in pharmacies and is used to rule out the presence of group A streptococcal bacteria, which can cause strep throat and other infections (including scarlet fever, abscesses and pneumonia) in a matter of minutes.

If it comes out positive, the doctor could prescribe an antibiotic, if it comes out negative there is a greater chance that it is a virus, these disappear on their own without having to be treated with antibiotics.

But it could also be COVID, so it is not so simple, but the Streptotest would help us rule out this other possibility.

The most common symptoms of COVID-19 arefever, dry cough and tiredness.
Other less common symptoms that affect some patients areaches and pains, nasal congestion, headache, conjunctivitis, sore throat, diarrhea, loss of taste or smell, and rashes or color changes in the fingers or toes.
These symptoms are usually mild and begin gradually.
Some of those infected have only very mild symptoms, according to the World Health Organization (WHO)

Patients with COVID-19 may spread infection prior to symptom presentation, during the symptomatic course, and during the clinical recovery period.
Many patients start out asymptomatic and as the days go by they begin to experience symptoms.
That is why at first they can spread the disease without being aware of it.

The common cold and COVID-19 have a gradual course to the presentation of symptoms compared to the flu that is caused by the various strains of influenza (orthomyxovirus family).

High temperature is rare in the common cold, but it is the most noticeable symptom in both COVID-19 and the flu, also if it is a bacterial infection.
The presentation of cough and fatigue is rare in the common cold.
Symptoms such as rhinorrhea and nasal congestion are prevalent in the common cold and are rare in the flu and COVID-19.

COVID-19 presents itself similarly to the flu (influenza), as both are diseases of the respiratory system.
In both diseases, the clinical presentation can vary from asymptomatic to severe pneumonia .
Además, tanto el COVID-19 como la influenza se transmiten por contacto, gotitas y fómites.
Por lo tanto, las técnicas de higiene de manos y las normas respiratorias similares serán beneficiosas para prevenir la propagación.

Another factor that influences the rate of spread of any infection is the basic reproduction number (R).
The influenza virus has an Rₒ of ~1.3 while the SARS-CoV-2 virus has an Rₒ of ~2.3. Therefore, each COVID-19 patient can spread 1.8 times more new contacts compared to influenza patients.

Compared to SARS (caused by the SARS-CoV-1 virus), some patients with COVID-19 (caused by the SARS-CoV-2 virus) may be infectious during their incubation period even in their asymptomatic stage.

The time from the advent of exposure to a pathogen to the clinical manifestation of the disease is called the incubation period. The increased incubation for COVID manifestation coupled with the ability to transmit infection during this period explains how rapid the potential spread of SARS-CoV-2 can be.

How they are transmitted

To find out what are the symptoms that would help us differentiate being infected by COVID-19 or flu or having a common cold, I have prepared a table based on different publications, and with some discrepancies given that in not all studies carried out the % of the frequencies of certain symptoms are similar, as some find a sore throat quite frequent, mucus, diarrhea and headache and others find it uncommon in the case of COVID-19.

For this reason, this table aims to be a summary that goes from more intense color in the most frequent symptoms to less intense color in the less frequent symptoms.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7138423/

Symptoms

According to a June 2020 post: Zayet S, Kadiane-Oussou NJ, Lepiller Q et al.
Clinical Features of COVID-19 and Influenza: A Comparative Study on the Nord Franche-Comte Group [published online ahead of print, June 16, 2020].
Microbes infect.
2020; S1286-4579 (20) 30094-0.
doi: 10.1016 / j.micinf.2020.05.016

The chronology would be as follows