COVID-19: Clinical presentation and incubation

Some coronaviruses, including COVID-19 (SARS-CoV-2), are pathogenic to humans.

The clinical presentation can be very variable, ranging from asymptomatic infection to infection with mild symptoms, and severe infection requiring an intensive care stay.

Main symptoms of COVID-19 infection

Transmission occurs mainly by air or by direct or indirect contact, and the respiratory tract is the main source of entry of the virus into the human body. The nose and upper respiratory tract are where the virus concentration is greatest when infected.

So it makes sense to think that many SARS-CoV-2 infections will cause symptoms consistent with the common cold, which is not wrong. Before the appearance of this form of coronavirus, this family of viruses was already often involved in cases of common cold, just like the rhinovirus, for example.

SARS-CoV-2 infection can cause a variety of symptoms, ranging from milder symptoms such as a stuffy nose with runny nose or sore throat, to more severe symptoms with coughing and difficulty breathing; a loss of smell or taste can also be a sign of the infection. Possible general symptoms are fever (over 38 degrees), muscle pain, headache, and fatigue or great weakness, among others. The infection can also affect other systems, such as the digestive system (vomiting, nausea, diarrhea). This list of questions is usually the one asked when a patient contacts a clinic to make an appointment, in addition to checking the exposure criteria. It is also possible to consult a self-assessment tool put in place by the Government of Quebec: quebec.ca/en/health/health-issues/a-z/2019-coronavirus/covid-19-symptom-self-assessment-tool/.

As SARS-CoV-2 can affect multiple systems, the full list of possible signs and symptoms would be too long to describe here; please consult government or World Health Organization websites for details and updates.

The diagnosis is suspected as soon as certain symptoms are present (although it is possible or even probable in some cases that the symptoms are due to some other reason), and a confirmatory test is then required to confirm the diagnosis. In the presence of a pandemic, people with suspicious symptoms (even if it is only a nasal congestion with a sore throat, of mild appearance, or an exacerbation of chronic lung disease) must consult only in “hot zones”, that is to say in designated places. These people should not come to a “cold zone”, such as in non-designated medical clinics.

Consequently, several appointments with health professionals are offered by teleconsultation in an attempt to meet the needs in this context (this also makes it possible to reduce the number of people in a clinic, and therefore to reduce the risk of transmission). Following the teleconsultation, if the healthcare professional judges that a physical examination is required, the patient will be directed to the correct resource, such as a Designated Assessment Clinic (CDE). People can also contact 811 or 1-877-644-4545. Emergency rooms are also organized with separate zones (“cold zone”, “warm zone” and “hot zone”), which helps reduce the risk of transmission if a patient has to present to the emergency room.

Factors that influence the severity of the infection

In the most severe cases, the virus can affect several organs or systems, with a higher probability of complications such as shock, respiratory failure, cardiac or vascular complications, or inflammatory complications.

There are many factors that influence the severity of the disease; among these, advanced age, the presence of chronic diseases (such as cardiovascular disease, diabetes, high blood pressure, chronic lung disease, cancer or chronic kidney disease), the presence of immunosuppression, obesity and smoking. Certain characteristics in laboratory tests or imaging can also have negative predictors.

Usually, patients who need to be hospitalized in intensive care or intubated will have a much longer recovery period than people who have a milder form of the infection.

Incubation period

The incubation period (i.e. the time it takes for the virus to start due to clinical symptoms) is usually 14 days or less, with a majority of symptoms appearing after 4 to 7 days, according to the data available to date.

This is why an isolation period is recommended in many circumstances.

It is important at all times to follow the sanitary instructions and directives in place.

Sources et références

• UpToDate, Coronavirus disease 2019 (COVID-19): Clinical features, mise à jour octobre 2020.
• https://www.who.int/health-topics/coronavirus
• https://www.canada.ca/fr/sante-publique/services/maladies/2019-nouveau-coronavirus/professionnels-sante.html
• https://www.quebec.ca/sante/problemes-de-sante/a-z/coronavirus-2019/