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Various categories of coronavirus disease 19 (COVID-19) patients have exhibited major mortality rate differences and symptoms. Some papers have recently explained these differences in mortality rates and symptoms as a consequence of this virus infection acting in synergy with one or more latent pathogen infections in some patients. A latent pathogen infection likely to be involved in millions of these patients is the protozoan parasite Toxoplasma gondii , which infects approximately one third of the global human population. However, other papers have concluded that latent protozoan parasite infections can reduce the severity of viral infections. The aims and purposes of this paper include providing explanations for the contradictions between these studies and introducing a significant new category of T-cell exhaustion. Latent pathogens can have different genetic strains with great differences in their effects on a second pathogen infection. Furthermore, depending on the timing and effectiveness of drug treatments, pathogen infections that become latent may or may not later induce immune cell dysfunctions, including T-cell exhaustion. Concurrent multiple pathogen T-cell exhaustion is herein called "polyspecific T-cell exhaustion." • COVID-19 patients exhibit mortality rate differences probably from latent pathogen infections. • Toxoplasma gondii infects about one third of the global human population and it is likely involved. • Latent pathogens have different genetic strains & different effects on later pathogen infections. • Drug treatments affect pathogen infections causing immune dysfunctions, e.g. T-cell exhaustion. • "Polyspecific T-cell exhaustion" enables concurrent multiple pathogen T-cell exhaustion. [ABSTRACT FROM AUTHOR]