ABSTRACT
Abbreviations: CMI - cell-mediated immunity, CMV - cytomegalovirus, CFS - chronic fatigue syndrome, DTH - delayed type hypersensitivity, EBV - Epstein-Barr virus, HIV - human immunodeficiency virus, HSV - herpes simplex virus, MW - molecular weight, NPC - nasopharyngeal carcinoma, SAIDS - simian AIDS, SARS - severe acute respiratory syndrome, SIV - simian immunodeficiency virus, TF - transfer factor, VZV - varicella zoster virus, WHO - World Health Organisation. According to the CDC (Centers for Disease Control and Prevention in the USA) estimates, asymptomatic infections represent 40 % of the total number. Cardiomyopathies and lung lesions are also observed in asymptomatic patients, whereas cases of Kawasaki's disease have been described in children (Gattinoni et al., 2020;Harahsheh et al., 2020;Lauer et al., 2020;Meng et al., 2020;Zheng et al., 2020). [...]certain patients, months after having recovered from the infection, present symptoms reminiscent of those of the chronic fatigue syndrome (CFS), whose aetiopathology is not totally understood, although certain herpes viruses, viz. Be that as it may, as long as an effective vaccine is not available, the world will be exposed to successive outbreaks of Covid-19;its fading out by protective 'herd immunity' requires acquisition of immunity by 70 % of the population, far from the 25 % observed today in the worst infected areas. [...]even if the rate of new infections may periodically seem declining in various areas, as long as the virus continues to circulate and a vaccine is not available to be used worldwide, the present pandemic may persist, with possible successive waves or ripples of new infections occurring episodically, as in the case of the seasonal flu and as it has been observed in the USA.