The increasing ratio of ageing population poses new challenges to healthcare systems. The elderly frequently suffer from severe infections. Vaccination could protect them against several infectious diseases, but it can be effective only if cells that are capable of responding are still present in the repertoire. Recent vaccination strategies in the elderly might achieve low effectiveness due to age-related immune impairment. Immunosenescence affects both the innate and adaptive immunity.

The roseoloviruses, human herpesvirus (HHV)-6A, HHV-6B, and HHV-7, can cause severe encephalitis or encephalopathy. In immunocompetent children, primary HHV-6B infection is occasionally accompanied by diverse clinical forms of encephalitis. Roseolovirus coinfections with heterologous viruses and delayed primary HHV-7 infection in immunocompetent adults result in very severe neurological and generalized symptoms. Recovery from neurological sequelae is slow and sometimes incomplete. In immunocompromised patients with underlying hematological malignancies and transplantation, frequent single or simultaneous reactivation of roseoloviruses elicit severe, lethal organ dysfunctions, including damages in the limbic system, brain stem, and hippocampus. Most cases have been due to HHV-6B with HHV-6A accounting for 2–3%. The most severe manifestation of HHV-6B reactivation is post-transplantation limbic encephalitis. Seizures, cognitive problems, and abnormal EEG are common. Major risk factors for HHV-6B-associated encephalitis include unrelated cord blood cell transplantation and repeated hematopoietic stem cell transplantation. Rare genetic disorders, male gender, certain HLA constellation, and immune tolerance to replicating HHV-6 in persons carrying chromosomally integrated HHV-6 might also predispose an individual to roseolovirus-associated brain damage. At this time, little is known about the risk factors for HHV-7-associated encephalitis. Intrathecal glial cell destruction due to virus replication, overexpression of proinflammatory cytokines, and viral mimicry of chemokines all contribute to brain dysfunction. High virus load in the cerebrospinal fluid, hippocampal astrogliosis, and viral protein expression in HHV-6B-associated cases and multiple microscopic neuronal degeneration in HHV-7-associated cases are typical laboratory findings. Early empirical therapy with ganciclovir or foscarnet might save the life of a patient with roseolovirus-associated encephalitis.

The sharp increase of life expectancy and the increasing ratio of ageing population pose new challenges for the public health system. The elderly suffer from more frequent and severe infections than young people. Theoretically, vaccination could protect the elderly against several infectious diseases, but due to their age-related immune impairment, vaccination might fail in many cases. Instead of ineffective vaccination campaigns, exploration and restoration of age-dependent dysregulation of their immune functions have to be placed into the focus of recent research. Frequent comorbidities in these people augment immune defects. Immunosenescence affects both the innate and adaptive immunity. Disturbances in macrophage-derived cytokine release and reduction of the natural killer cell mediated cytotoxicity lead to increased frequency of respiratory, gastrointestinal and skin infections. Although the humoral immunity retains most of its original activity through life span, ageing dampens the ability of B cells to produce antibodies against novel antigens. Age-related declination of the cellular immunity is the consequence of thymic atrophy, reduced output of new T lymphocytes, accumulation of anergic memory cells, deficiencies in the cytokine production and uncertain antigen presentation. Persistent infection by different herpesviruses and other parasites contribute to the loss of immunosurveillance and premature exhaustion of T cells.

A new variant of SARS-CoV-2 named Omicron (B.1.1.529) was isolated from an HIV-infected patient in Botswana, South Africa, in November 2021. Whole genome sequencing revealed a multitude of mutations and its relationship to the mutation-rich Alpha variant that had been isolated from a cancer patient. It is conceivable that very high prevalence of HIV-infected individuals as susceptible hosts in South Africa and their immunocompromised state may predispose for accumulation of coronavirus mutations. Coronaviruses uniquely code for an N-terminal 3′ to 5′exonuclease (ExoN, nsp14) that removes mismatched nucleotides paired by the RNA dependent RNA polymerase. Its activity depends preferably on Mg²⁺ and other divalent cations (manganese, cobalt and zinc). On the contrary, methyl transferase activity of non-structural protein (nsp) 14 and nsp16 both complexed with nsp10 requires Mn²⁺. Enzymes in successive stages of HIV infections require the same cations. In HIV-infected organisms, a subsequent coronavirus infection encounters with altered homeostasis of the body including relative starvation of divalent cations induced by interleukin production of HIV-infected cells. It is hypothesized that selective diminished efficacy of ExoN in the absence of sufficient amount of magnesium may result in the accumulation of mutations. Unusual mutations and recombinations of heterologous viruses detected in AIDS patients also suggest that long-lasting persistence of superinfecting viruses may also contribute to the selection of genetic variants. Non-nucleoside reverse transcriptase inhibitors partially restore divalent cations’ equilibrium. As a practical approach, implementation of highly active antiretroviral therapy against HIV replication and vaccination against coronaviruses may be a successful strategy to reduce the risk of selection of similar mutants.

The incidence and number of species involved in the spectrum of sexually transmitted infections continue to increase. Laboratories have to be prepared for identification of unusual microbes. In our practice, a male patient had recurring urethritis and balanitis after having repeated unprotected insertive sexual intercourse with female piglets. He also had allergy to scents and some metals, otherwise he showed no general symptoms. Specimens were swabbed from the urethra, inflamed glans, rectum, mouth onto several culture media, subsequently isolates were tested for their morphology, biochemical activity. Kurthia gibsonii was isolated from urethra and glans. No concomitant infection with other microbes was detected, haemoculture was negative. Relying upon antibiotic sensitivity test, he was cured with 2 × 500 mg oral cefuroxime for 15 days, and topical gentamycin cream for 2 months. This is the first reported sexually transmitted, zoonotic infection without generalization by Kurthia spp. We report first the antibiogram of K. gibsonii. Slight differences in the antibiotic sensitivity suggest independent infection and sensitivity of urethral and mucous membrane tissues to distinct K. gibsonii strains. Allergy of the patient might predispose to opportunistic infection. Such aspects ought to be tested in details in further cases.