COVID-19

How is it transmitted?

It is almost exclusively transmitted through respiratory droplets (i.e. spit) at short distances or through aerosols (airborne particles) at long distances.

It is not transmitted through skin-to-skin contact, although it is possible to contract the disease if you touch an infected person and then touch your eyes, nose, or mouth.

See https://www.canada.ca/en/public-health/services/diseases/2019-novel-coronavirus-infection/health-professionals/main-modes-transmission.html

How infectious is it?

The infectiousness of a disease is quantified by predicting how many other people the typical patient will infect. This is called the basic reproduction number, or \(R_0\). It is challenging to measure this number exactly, but COVID-19 is likely to have a \(R_{0}\) value of just under 3.

Are you more likely to contract the disease from droplets or from aerosols?

It is not yet clear.

Is wearing masks effective?

Masks are effective at stopping respiratory droplets, so they work well at preventing transmission between two people in close proximity (≅2m).

Conventional masks are not effective at preventing aerosol transmission, and so adequate ventilation is extremely important in building with poor airflow.

How deadly is it?

The mortality rate is around 1–3% for most developed countries with good healthcare.

However, these values are relatively low because of the preventative measures that these countries have put in place. Earlier in the pandemic, the mortality rate was much higher. For example, France peaked at a mortality rate of almost 25%.

See https://ourworldindata.org/explorers/coronavirus-data-explorer?zoomToSelection=true&time=2020-03-01..latest&pickerSort=desc&pickerMetric=new%5Fdeaths%5Fper%5Fmillion&Metric=Case+fatality+rate&Interval=7-day+rolling+average&Relative+to+Population=true&Align+outbreaks=false&country=IND~USA~GBR~CAN~DEU~FRA