Chapter 38: Viral & Prion Diseases in Humans

Viral & Prion Diseases in Humans microbiology chapter explores major human diseases caused by viruses and prions, organizing them by transmission route. Airborne pathogens include the highly contagious Measles and Influenza, detailing the latter’s mechanisms of rapid genetic change through antigenic drift and shift. The chapter also covers the latent herpesvirus infections, such as Varicella-Zoster Virus (VZV) causing chickenpox and reactivating as shingles, and the eradication success story of Smallpox. Arthropod-borne viruses (arboviruses) like West Nile, Zika (notable for causing microcephaly in fetuses), and Dengue are discussed, highlighting the dangerous phenomenon of Antibody-Dependent Enhancement (ADE) that can lead to Dengue Hemorrhagic Fever. Diseases spread via direct contact feature prominently, particularly HIV, a retrovirus that establishes chronic infection and compromises the immune system by targeting CD4+ T cells, leading to AIDS. This section also examines various herpes simplex viruses (HSV-1 and HSV-2) responsible for cold sores and genital lesions that periodically reactivate from neural latency. Critical viral hepatitides, including vaccine-preventable Hepatitis B (a reverse-transcribing DNA virus) and Hepatitis C (an RNA virus that is often curable with modern drugs), are examined, along with Human Papillomavirus (HPV), which causes warts and is linked to several cancers. Furthermore, food and waterborne diseases, such as viral gastroenteritis caused primarily by Norovirus and Rotavirus (which is vaccine-preventable in children), and the history and ongoing global eradication efforts against Poliovirus are detailed. The discussion concludes with zoonotic pathogens transmitted from animals, including the lethal hemorrhagic fever viruses Ebola and Marburg, and Rabies, emphasizing the need for post-exposure immunization. Finally, the chapter addresses transmissible spongiform encephalopathies (TSEs), fatal neurodegenerative disorders caused by proteinaceous infectious particles known as prions, such as Creutzfeldt-Jakob disease.