SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the etiological agent of COVID-19 (coronavirus disease 2019), caused a pandemic of such a magnitude that it led to the collapse of healthcare institutions and economic and social fracturing; the term “post-COVID-19” has become part of daily conversation in various areas of life.

In terms of health, “post-COVID-19” is used to refer to the persistence of signs and symptoms in individuals who have passed the acute phase of the infection. Once the disease has been overcome, it is estimated that from 10% to 20% of individuals will continue to have a series of symptoms such as fatigue, headache, anxiety, “brain fog,” insomnia, cough, dyspnea, chest pain, arthralgia, myalgia, and diarrhea (among others). All these symptoms fluctuate and are heterogeneous in their characteristics and intensity1.

This set of signs and symptoms that persist following COVID-19 has been referred to in a variety of ways over the past year: post-COVID-19 syndrome, post-COVID conditions, long COVID, persistent COVID, post-acute COVID-19, post-acute sequelae of COVID-19, long-haul COVID, and chronic post-COVID syndrome, to cite just the most noteworthy (Table 1).

So what are we talking about when we talk about “post-COVID-19” manifestations? The first guidelines published used the designation “post-COVID-19 syndrome” to refer to the signs and symptoms that develop during or after the infection which continue for more than 12 weeks and which cannot be explained by an alternative diagnosis. They also use the term “long COVID” to refer to the clinical symptoms that follow the acute phase (four weeks) and continue beyond 12 weeks (encompassing post-COVID-19 syndrome)1.

Later, the World Health Organization and the Centers for Disease Control and Prevention used the term “conditions” to refer to post-COVID-19 manifestations, with the World Health Organization assigning the ICD-10 code U09.9 for post-COVID conditions. More recently, various scientific and patient organizations have used the terms “long COVID” and “persistent COVID” without the “post-” prefix, given that it refers to a disease which has been overcome, which is in contrast to the pathogenic hypothesis of the existence of reservoirs with viral persistence2.

None of the proposed terms is entirely accurate; all have strengths and weaknesses and an agreement has yet to be reached on how to define this situation. What remains to be determined is:

• a)

  The name that best identifies it.

• b)

  The time periods to consider for its start (3, 4, 12, 24 weeks).

• c)

  The signs and symptoms that should be included, given that in the etiopathogenesis, presence of the following must be clarified: 1) sequelae due to fibrosis and thromboembolism, 2) persistent inflammation, 3) autoimmune reactions, and 4) persistence of intestinal viral reservoirs.

• d)

  Confirmed, probable, or possible entities should be considered based on the type of study that verifies the presence of SARS-CoV-2 infection (RT-PCR, antigen detection test, antibody detection)3,4.

From a clinical-pathological point of view, it overlaps with the coexistence of manifestations due to a) sequelae induced by SARS-CoV-2 (fibrosis, thrombosis); b) manifestations related to persistent inflammatory activity (systemic inflammation, autoimmune reactions, or SARS-CoV-2 persistence); and c) sequelae of hospitalization, mainly in those who required intensive care unit (ICU) care3,4.

Considering this variability, it is possible to distinguish the following clinical phenotypes:

• a.

  Predominantly respiratory pattern (those treated in the ICU, pulmonary fibrosis, organizing pneumonia).

• b.

  Cardiorespiratory pattern with cardiovascular symptoms and a lesser degree of lung damage (non-hospitalized patients, chest pain, tachycardia, postural orthostatic tachycardia syndrome, imaging tests, and lung function without significant damage).

• c.

  Psychoneurocognitive pattern (altered memory, “brain fog,” insomnia, anxiety, depression, headache).

• d.

  Pattern with persistent inflammatory activity, which can be concomitant with the above patterns3,4.

It is possible that post-COVID-19 syndrome, long COVID, persistent COVID, and other terms used in the literature represent multiple syndromes that are the result of past or persistent pathological processes, of which is its essential to learn the etiopathogenesis.

At present, it is possible to use an umbrella term that encompasses post-COVID-19 manifestations and understand it, at least for the time being, as a concept or various concepts under construction, with certainties, unknowns, and overlapping, until it can be redefined in light of conclusive scientific evidence.

The answers will come from research, which must draw from clinical practice with the emergence of multidisciplinary post-COVID-19 groups, units, and clinics that allow for determining all clinical profiles in depth and examining the model to identify phenotypes that allow for better establishing prognosis and using treatments tailored to each clinical profile.