COVID-19 is an infectious disease caused by an emergent virus known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease causes acute respiratory illness. SARS-CoV-2 was detected in December 2019 in China and spread worldwide, with currently more than 768,187,096 confirmed cases and 6,945,714 deaths (as of June 21st, 2023)1. Despite specific vaccines and drugs, COVID-19 is an ongoing pandemic and many clinical trials evaluating potential treatments are in progress.

What are coronaviruses?

Coronaviruses are a diverse family of enveloped, single-stranded RNA viruses that infect humans, as well as a wide range of animals. The name comes from the Latin term for a crown (corona) due to the morphology of viral particles with a core shell and surface projections resembling a solar corona. Coronaviruses pose a high risk for both public health and economy. COVID-19 is the third known zoonotic (spread from animals to humans) coronavirus disease after the outbreaks of SARS in 2002/2003 and the Middle East Respiratory Syndrome (MERS) in 20122.

Origin of SARS-CoV-2

The COVID-19 outbreak has been traced back to the Huanan Seafood Wholesale Market3. The animal host responsible for the original transmission event to humans is not known; however, it is likely that horseshoe bats are the natural reservoir species of the SARS-CoV-2 progenitor4. Since 2019, SARS-CoV-2 has spread all over the world, transmitting from person to person1.

Symptoms of COVID-19

Following symptoms are associated with COVID-19 according to the WHO5:

Most common symptoms:

Less common symptoms:

Serious symptoms:

Emerging SARS-CoV-2 variants, together with general immunization status, might have altered the prevalence of COVID-19 symptoms6.

Most infected people develop mild to moderate symptoms and recover without hospitalization. However, some people, including the elderly and people with previous medical issues (such as diabetes, cardiovascular disease, chronic respiratory disease, cancer), are at higher risk of developing severe symptoms that could ultimately lead to death7.


Evidence suggests that SARS-CoV-2 spreads primarily via aerosol emitted during respiratory activities including breathing, talking or coughing. Virus-containing droplets and surface contamination likely have only a limited effect on the spread of the infection. The lifetime of airborne viral particles is dependent on environmental factors such as humidity, temperature, and ultraviolet radiation8.

Several preventive measures are considered to be effective in limiting the spread of SARS-CoV-2. When social distancing is not possible, medical masks limit dispersion of the virus into the environment. Proper ventilation is crucial to limit the concentration of airborne particles indoors. Only masks with proper fit, made from certified materials, and worn for an adequate period of time guarantee a high degree of protection for the wearer. Regular hand washing/disinfection might contribute to the protection from the infection, as well9.

A global effort has led to the development of several safe COVID-19 vaccines capable of saving lives and limiting the viral spread. Combined with aforementioned physical preventive measures, vaccines provide the optimal way to tackle the COVID-19 pandemic10.