We explain what is the morbidity or morbidity of a disease and the differences with mortality. Also, morbidity rates.
What is morbidity?
In epidemiology and statistics, morbidity or morbidity is the proportion of individuals who contract a specific disease in a given place and time frame. That is, it is about the frequency of onset of the disease with respect to population: the higher the morbidity rates from a disease, the greater the number of persons afflicted by it within the period taken into consideration.
This term comes from the Latin word morbidus, which means "sick", and expressed in percentage terms, is one of the most useful indicators when planning strategies for public health, for example, when dealing with an epidemic. Not to be confused with mortality, a totally different statistical indicator.
Morbidity rates
Commonly, two different morbidity rates are used, depending on the specific information that is needed:
- Prevalence rate. It refers to the total frequency of cases of the disease, both new and old, that are registered at a certain point in time (point prevalence) or over a period (period prevalence).
- Incidence rate. Instead, it refers to the speed with which the disease spreads, that is, the rate of contagion or at least the number of new infections during a certain period of time.
In both cases, the computation of the morbidity rate of a disease is always accompanied by the information of the period studied and the geographic region affected.
Morbidity and mortality
If the morbidity rate refers to the rate at which a disease spreads in a certain period and in a specific area, the mortality rate refers to the number of deaths that occur in a certain area and period.
This mortality can refer either to all deaths, whatever their cause (general mortality rate), or to deaths resulting from a specific cause (particular mortality rate).
Thus, in epidemiology, it is common to study a disease both from its morbidity rate (number of registered cases) and mortality (number of deaths caused by it), in order to get an idea, from statistics, of how lethal is the disease and how easily it is spread.