##### < Propagation

# How to succeed in deconfinement?

Text updated on 2020-05-03

**
Through my individual behaviour, I have the power to help limit the spread of the SARS-CoV-2 coronavirus and thus limit the number of deaths, move out of the social containment phase, and support the recovery of my country. I choose responsible behaviour!
**

The reproduction index, R0, is the average number of people infected with COVID-19. This index determines the rate of infection, i.e. without epidemic control measures, the proportion of the population that will be infected will exceed 1 - 1 / R0. If, for example, R0 = 2.5, then at least 60% of the population will be infected. In this scenario, based on the mortality rate of infected people estimated in France or the United States to be ~ 0.5%, and assuming that the health care system is not overwhelmed, then more than 3 people per 1000 will die in COVID-19 the population if we do not succeed in reducing the average number of people infected by a COVID-19.

The lower the reproduction number, R0, the slower the spread of the epidemic, the more we can guarantee the care of the sick and protect the nursing staff, the more time we save in finding effective therapies and reducing the number of victims.

It is therefore vitally important for all of us to try to reduce R0 as much as possible:

- reduce the proportion of infected people to achieve herd immunity,
- avoid a new peak of contamination too overwhelming for the sanitary systems
- buy time before the arrival of COVID-19 treatments or a vaccine.

There is, of course, a lot of uncertainty about the parameters that control the reproduction index. Nevertheless, since the virus is transmitted via hand contact with surfaces contaminated by the virus, via droplets of saliva or aerosols :

- Wearing masks can significantly reduce the flow and number of droplets excreted,
- by implementing barrier gestures,
- Regular hand washing reduces the likelihood of being contaminated by viruses 'deposited' on contaminated surfaces.

**Barrier gestures and the wearing of masks therefore help slow the spread of the virus, which will ultimately save lives and allow our country's economy to get back on its feet more quickly.**

__Sources__

Epidemiological study on the Oise "cluster" population where many cases were infected in a high school estimating R0 = 3.3.

Salje, H., Kiem, C. T., Lefrancq, N., Courtejoie, N., Bosetti, P., Paireau, J., ... & Le Strat, Y. (2020). Estimating the burden of SARS-CoV-2 in France.An American study showing that R0 = 5.7 in Wuhan at the beginning of the epidemic.

Sanche, S., Lin, Y. T., Xu, C., Romero-Severson, E., Hengartner, N., & Ke, R. (2020). High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2. Emerging Infectious Diseases, 26(7).The proportion of the population that will be infected exceeds 1-(1/R0) when the epidemic is not under control.

ETE Modelling Team (MIVEGEC, Univ. Montpellier, CNRS, IRD). Herd immunity & epidemic final size. March 17th, 2020.