Cognitive and neuropsychiatric disorders are common, with an estimated 55 million people suering from dementia globally (World Health Organization, 2021) and an estimated 15.56 percent of community- dwelling adults over age 50 years having mild cognitive impairment (Bai et al., 2022), estimates that indicate a substantial global burden of cognitive dysfunction. As the ndings presented throughout this book suggest, a range of infectious diseases including viral, bacterial, and parasitic infec­tions have been associated with cognitive impairment and neuropsychiatric impair­ment and neuropsychiatric disorders and could be considered critical risk factors for cognitive and neuropsychiatric disease. Moreover, viral infections including herpes simplex virus 1 appear to generate some of the pathological changes associ­ated with Alzheimer’s disease, and increasingly infectious diseases including viruses have been associated with dementia and cognitive decits (Damiano et al., 2022). Severe acute respiratory syndrome coronavirus 2 (SARS- CoV- 2, Covid- 19), which has infected over a quarter of a billion people, might result in neurodegenerative changes (Damiano et al., 2022), although the current novelty of Covid- 19 precludes knowing whether it will become a risk factor for the development of Alzheimer’s disease or other dementias. Given the numbers of current and projected cases of Alzheimer’s disease and in that as of this writing little if any progress has been made in disease- modifying treatments, prevention of Alzheimer’s disease and other types of dementia becomes all the more crucial. As such, any insight into potentially pre­ventable causes of Alzheimer’s disease and other neurodegenerative diseases such as infectious diseases is important for research agendas. In this regard, treatment with antiviral medication in patients with herpes simplex virus appears to lower the risk for Alzheimer’s disease (De Vlieger et al., 2022).

notion of PANDAS to a similar conceptualization known as pediatric acute neuro­psychiatric syndrome (PANS), which has been associated with viruses such as Borna virus disease, bacteria such as Borrelia burgdorferi (Lyme disease), and the parasite Toxoplasma gondii (Endres et al., 2022).

diagnosis of infectious diseases that can aect the brain; the pathogenesis of be­havior, neurological, and cognitive problems associated with infectious diseases; methods of prevention including basic public health measures such as sanitation and vaccination; treatment; and neurological and cognitive rehabilitation for those suering from cognitive and behavioral problems resulting from infectious diseases (John et al., 2015). For many if not most infectious diseases, basic questions such as understanding the reasons why some people with exposure to an infectious disease can remain asymptomatic, whereas others may suer from chronic problems with cognitive function, remain.

In addition to the current neurocognitive and neuropsychiatric burden associated with infectious diseases, it is possible that the numbers of people exposed to some infectious diseases might increase in conjunction with climate change. A warming climate aggravated in some cases by poverty is expanding the range of some infec­tious diseases and increasing the risk of exposure to infectious diseases, potentially putting people at risk to infectious diseases from regions to which they had not pre­viously been exposed. Autochthonous acquisition of mosquito- borne infectious diseases such as dengue, Zika, and chikungunya has occurred in the southeastern United States (Hotez & LaBeaud, 2023), putting more people at risk for contracting these viral diseases, which is important as chikungunya virus has been associated with decits in cognitive function (Peixoto et al., 2022).

diseases may interact with each other to aect cognitive and psychiatric function, and general health and development. It is possible that interactions may occur be­tween pathogens, as indicated in Chapter 20 in this volume concerning interactions between viruses that result in multiple sclerosis. Associations between infectious diseases and neurocognitive and neuropsychiatric disease increasingly implicate immunological involvement and inammation with cognitive and neuropsychiatric function (Damiano et al., 2022). In this regard, Endres et al. (2022) have proposed that there might be an immunological subtype of obsessive– compulsive disorder, a subtype not only involving immune function but exposure to infectious diseases as well. In fact, it is possible that immune- related sequelae of Covid- 19 infection could be associated with obsessive– compulsive disorder (Endres et al., 2022). Infectious diseases may aect cognitive and neuropsychiatric functions through a variety of mechanisms in addition to altering immunologic function, including direct eects of an infectious pathogen on the brain and epigenetic eects (Damiano et al., 2022). However, more research into mechanisms about how infectious disease is required not only to better understand the pathophysiology underlying the associations be­tween infectious disease and decits in cognitive and neuropsychiatric function but also to provide insights and guidance into prevention and treatment.