Acute respiratory diseases caused by viruses or bacteria usual get resolved quickly and patients recover fast. Namely, even people who survived MERS or the first SARS, caused by another coronavirus, recovered after intensive treatment, and no subacute or chronic sequalae of the disease were noted. COVID-19, induced by the SARS-CoV-2 virus, behaved very differently, since about 3–30% of acute COVID-19 patients complain about shortness of breath, fatigue, headache, ‘brain fog’, muscle weakness and general fatigue more than 4 weeks after the initial infection. Or, even worse, some patients who have completely recovered show up with these nonspecific, multiorgan signs and symptoms. More alarming is the recent recognition that vaccination against SARS-CoV-2 does not offer protection, i.e., it may reduce the risk of long COVID, but it does not eliminate it. Needless to say, the pathogenesis of long COVID is poorly understood and no specific treatment is available; only symptomatic relief that makes both patients and clinicians very frustrated.

Because of the wide-spread, worldwide occurrence of the long COVID syndrome (LCS), we organized in 2022 a symposium on long COVID, with international participation, at the Hungarian Academy of Sciences. We then asked participants to prepare short original or review articles on their presentations that appear in this special issue of Inflammopharmacology, thanks to its forward looking editor Prof. Kim Rainsford. Namely, despite of our insufficient understanding of the molecular and cellular mechanisms of LCS, we know that it is a multiorgan inflammatory process, perpetuated by cytokine storm and complicated by multiorgan thrombi. due to the damage of vascular endothelial cells. By disseminating information about the manifestation, clinical and public health aspects, as well as the ‘little we know’ about the pathogenesis of LCS, thanks to the generosity of Inflammopharmacology, we hope this publication will not only generate more data collection about the clinical manifestations and epidemiology of long COVID, but also stimulate more clinical and basic research to better understand and treat more successfully this new syndrome of the twenty-first century.