What are the recurring terms related to information on COVID-19? Are we always sure we know its meaning? A glossary can help improve disease communication.


Home self-isolation
Cautionary measure that requires the stay of even asymptomatic individuals at their home, home or residence for a defined period of time, in order to contain an epidemiological emergency by preventing the spread of the infection. This measure can be ordered by the authority (eg. For people who come from areas with high epidemiological risk) or adopted on a voluntary basis based on their movements and contacts (eg if they believe they are at risk).

Contact tracing
In an epidemic situation, as part of both a containment strategy and a mitigation strategy, it is essential to identify all individuals who have been or may have been in contact with a confirmed or probable case of COVID-19, focusing the research of the same with particular attention to the 48 hours preceding the onset of symptoms up to the moment of diagnosis and case isolation.

The ability with which a disease or agent is transmitted naturally (direct or indirect contact) from an eliminating host (whether healthy or diseased) to a receptive host.

Collective Protective Equipment
Any device or system (e.g. ventilation systems, aeration, safety nets, temporary parapets or soundproofing systems) designed to protect workers from the risks present in the workplace.

Personal Protective Equipment
Any equipment intended to be worn and kept by the worker in order to protect him against one or more risks likely to threaten his safety or health during work, as well as any complement or accessory intended for this purpose.

Emission of respiratory and salivary secretions in the form of droplets, expelled when sneezing or coughing and sometimes even speaking, which remain suspended in the air with a variable relapse radius and the power to spread pathogens.

The frequent and localized, but limited in time, manifestation of an infectious disease, with a widespread transmission of the virus. The epidemic occurs when a sick person infects more than one person and the number of cases of the disease increases rapidly in a short time. The infection therefore spreads in a population consisting of a sufficient number of susceptible individuals.

Epidemic outbreak
We speak of an epidemic outbreak when an infectious disease causes an increase in the number of cases compared to what is expected within a community or a well-defined region.

The incidence considers the number of new events in a population in a given period of time. While prevalence describes the proportion of individuals in a population suffering from a disease at a specific time, the incidence describes the speed of movement from the state of health to the state of disease.

The incubation period represents the time that elapses between infection and the development of clinical symptoms.

Lethality and mortality
In medicine, the term lethality refers to the number of deaths out of the number of sufferers of a certain disease within a specified time. Lethality is a measure of the severity of a disease and is used especially for acute infectious diseases. Mortality, which is often mistakenly confused with lethality, is conceptually different and leads to very different results, as it relates the number of deaths for a given disease (or even for all causes) to the total average population present in the same observation period.

The pandemic is the spread of an infectious agent in several continents or in any case in large areas of the world. The pandemic phase is characterized by transmission to the majority of the population. According to the World Health Organization, COVID-19 is a pandemic.

Prevalence is the proportion of the population affected by the disease in question at a specific moment of time, thus indicating a photographic image of the population at the time of the survey.

It is a period of isolation and observation of varying duration that is required for people who could carry germs responsible for infectious diseases. The origin of the term quarantine refers to the original duration of forty days, which in the past was strictly applied especially to those coming from the sea. Today, the time indicated for quarantine varies according to the various infectious diseases, in particular relative to the incubation period identified for the specific infectious disease.

The so-called R0 (“r with zero”), that is the basic reproduction number, represents the average number of secondary infections produced by each infected individual in a completely susceptible population that is never in contact with the new pathogen. This parameter measures the potential transmissibility of an infectious disease. In other words, if the R0 of an infectious disease is 2, it means that on average a single patient will infect two other people. The higher the R0 value, the higher the risk of spreading the epidemic. If, on the other hand, the R0 value is less than 1, the epidemic will tend to self-contain.

Diagnostic replication index at different lags. This index allows you to know the percentage of positive diagnoses that are notified after a certain time interval (lag) from the previous diagnoses already notified.

The net playback number (Rt) calculated in the unit of time. RT allows for example to monitor the effectiveness of interventions during an epidemic.

Sensitivity and specificity
Sensitivity and specificity are two criteria used to evaluate the ability of a diagnostic or screening test to correctly identify those who have the desired disease and those who do not. The sensitivity of a test is its ability to correctly identify sick individuals. In terms of probability, sensitivity is the probability that a true patient will test positive, and therefore is referred to as the proportion of true patients who test positive. However, that a test has a high sensitivity is not enough: a good test must also identify as positive only those who have the disease; that is, it is necessary that among the positive tests are included as few as possible of those who do not have the disease (false positives). From this observation derives the concept of specificity. The specificity of a test is its ability to correctly identify subjects who do not have the disease. In terms of probability, specificity is the probability that an individual truly without the disease will test negative, so it is the proportion of people with the disease who test negative.

Asymptomatic subject
It is a subject who, despite being affected by a disease, does not present any apparent symptoms. A disease can remain asymptomatic for short or long periods; some diseases can remain asymptomatic forever. The presence of asymptomatic coronavirus patients also seems possible in the case of SARS-CoV-2, however, according to the World Health Organization, symptomatic people are currently the most frequent cause of spread of the virus.

Oropharyngeal swab
Test that allows to analyze the mucosa of the pharynx in order to identify the possible presence of pathogenic microorganisms, typically bacteria, but also viruses and fungi if necessary. It consists of introducing a cotton-coated stick inside the mouth, from which material is removed from the surface of the tonsillar mucosa which is then inseminated on culture material.

Serological test
Serological tests for Covid-19 are used to identify all those people who have come into contact with the virus. The antibodies that are sought are of two types, IgM and IgG immunoglobulins. The former are generally produced in the initial phase of the disease and then their value tends to drop. So if they are found in the blood, it means that the infection has just passed and the virus may still be present in the body. IgG, on the other hand, develop approximately between 9 and 11 days after the infection, and therefore, in most cases, if they are detected it means that the infection has already occurred for some time and the person tends to be immune to the virus. The serological test is useful as it allows to identify even people who have had mild symptoms or are even asymptomatic.


(sources: Istituto Superiore di Sanità, ASL VC, University of Eastern Piedmont, Epidemiology & Prevention, Regional Documentation Center for Health Promotion, Autonomous Province of Bolzano Alto Adige)