Coronavirus math

Events are being canceled and universities are extending spring break and moving classes online across the area. This is disappointing even frustrating, but this is not an overreaction, it's math.

Scientist quantify the spread of infectious disease with a basic reproduction number (R₀), pronounced "R naught". It describes the magnitude of an outbreak in how many new infections are expected from each existing one.

Coming up with the right R₀ to describe a disease is complex, involving many factors, especially early in an outbreak, according to Joseph Eisenberg, Professor and Chair of Epidemiology at the University Michigan School of Public Health. The number can also change as an outbreak progresses and ways of slowing progress are found and implemented.  The goal is simple, get the number under one as quickly as possible.

• R₀ > 1, outbreaks are expected to continue. The higher the number, the faster an epidemic spreads.
• R₀ < 1, outbreaks are expected to end.

According to the Centers for Disease Control and Prevention (CDC), a new disease like coronavirus can move quickly though a immunologically early in a naïve population with no natural immunity to fight it. Vaccines are in development, but many months away.

Coronavirus has been most recently observed with an R₀ of about 2.6. Several studies along with the World Health Organization's daily reporting on the spread suggest a doubling of cases every six days. This kind of exponential growth continues until the cycle is broken.

But the disease cant spread to a new host that isn't there. Canceling large gatherings of people helps drive R naught under 1 and an end of the epidemic.