# Definitions

Doubling Days – The number of days, going backward, when the current value was half of that.

HUR – Hospital Utilization Rate. The number of positive and suspected patients, divided by the total number of hospital beds for the locality.

IUR – ICU Utilization Rate. The number of patients in ICU, positive and suspected, divided by the total number of ICU beds available. The number of ICU beds available isn’t provided directly by the state of California. Instead, it is calculated as the sum of patients currently in ICU + the number of ICU beds available.

Daily ICU for positive patients only is defined by the state of CA as follows: “The number of laboratory-confirmed positive COVID patients that are in the ICU at the hospital. This includes all ICU beds (NICU, PICU, and adult).” Daily ICU for suspected patients is defined as: “The number of symptomatic patients, with tests for COVID pending laboratory confirmation, that are in the ICU at the hospital. This includes all ICU beds (NICU, PICU, and adult). “

The Daily ICU number I use is the total ICU number, the sum of suspected and positive. This is the number of patients in ICU on that particular day.

The other part of the equation is the number of ICU beds available, defined by the state as follows: “The number of ICU beds available at the hospital. This includes all ICU beds (NICU, PICU, and adult). “

So, the ICU Utilization Rate (IUR) is the Daily Total ICU patients, divided by the ICU beds available + the current ICU patient total. This is a key metric, because when IUR gets up around 80%, there’s major trouble ahead. It even very stressful on hospital staff if the typical IUR is around 10% and suddenly jumps to 20%. They’re still far below capacity, but it takes a lot of highly trained personnel, expensive equipment, etc., to run an ICU.

R0 – pronounced “R not”. The initial contagion rate of the virus in a naive population, that is, a population that has never been exposed to the virus and for which there is no vaccine. The R0 is fixed. For COVID-19, it is estimated to be between 2 and 3.

Rt  or Reff or R – Rt represents the effective reproduction rate of the virus calculated for each locale. It lets us estimate how many secondary infections are likely to occur from a single infection in a specific area. Values over 1.0 mean we should expect more cases in that area, values under 1.0 mean we should expect fewer. FAQ for rt.live.