How can the coronavirus COVID-19 be so contagious?
Discovered in December 2019 in China, the coronavirus 2 (COVID-19) is swiftly spreading at all around the world (affecting nearly 150 countries and territories up to 20 March 2020). But how can this virus be so contagious?
A recent study conducted by a team of researchers (Doremalen et al.), published on 17 March in the scientific journal The New England Journal of Medicine, sheds some light on the subject. This group of researchers compared the viability of SARS-CoV-2 (formerly called HCoV-19, now COVID-19) and SARS-CoV-1 in the air (aerosols) and on various surfaces.
Article and source: Neeltje van Doremalen et al. « Aerosol and surface stability of SARS-CoV-2 (HCoV-19) compared to SARS-CoV-1 ». The New England Journal of Medicine. DOI: 10.1056/NEJMc2004973 (2020). https://www.nejm.org/doi/10.1056/NEJMc2004973 (accessed 18 March 2020)
In their experiment, they used a three-jet Collison nebulizer and a Goldberg drum to create an atomized environment, similar to that observed in samples obtained from the upper and lower respiratory tract in humans.
Their data consisted of 10 experimental conditions involving two types of viruses (COVID-19 and SARS-CoV-1). Experiments were carried out in five environmental conditions (aerosols, plastic, stainless steel, copper, and cardboard) in order to evaluate the decay rates of the viruses, using a Bayesian regression model. Each experiment was repeated three replicates.
Synthesis of results:
The results show that COVID-19 and SARS-CoV-1 share similar stability and that the hypothesis of airborne and tactile transmission of COVID-19 is proven. The latter can survive in the air for several hours, and maintain its contagious capacities on the surfaces of objects for up to several days.
Aerosol: throughout the experiment (3 hours), the COVID-19 was still able to survive and presented infectious characteristics. Its « half-life » (time used to reduce half of its initial value) was approximately 2.7 hours.
Plastic: COVID-19 viable viruses can be detected up to 3 days (72 hours) after contamination of a surface. Although viral capacities decrease with time, it will take approximately 16 hours for the virus to reach its « half-life » phase.
Stainless steel: the viable virus can be detected up to 2 days (48 hours).
Cardboard: detected up to 1 day (24 hours).
Copper: detected up to 4 hours.
From the above scientific research results, we can understand why there are so many « familial cluster » and nosocomial spreading events because of COVID-19. For us, as each citizen, it seems necessary to take the following actions:
- Remain in confinement at home. Reduce outings as much as possible, even for necessities (e.g., one shopping every 10 days). Avoid going out every day to buy bread, walk or let the children play in the residence courtyard;
- Wash your hands, face, nose, and ears regularly with soap or gel for 20 seconds. Wear masks, gloves, scarves, hats, glasses, or other projection equipment when leaving home.
- Avoid, if possible, taking the elevator, bus, subway, any place with little or no ventilation likely to have viruses in the aerosol.
- Immediately disinfect, on your return home, all objects coming from outside with a disinfectant spray (alternative: 70-75% modified alcohol, diluted bleach, etc.): outdoor clothing, surfaces of any item purchased in stores, letters, packages, telephones, and laptops. If you have no disinfectant spray, after touching these objects, please wash your hands thoroughly (see N°2).
- Maintain good hygiene in your home (cleaning the floor, door handles, etc.) and air the rooms 2 to 3 times a day for 30 minutes.
- As the virus is sensitive to temperatures above 56°C, it is preferable to cook your food well and avoid eating raw vegetables. Boil tap water before eating.