Preface

The purpose of this audio-course is to provide you with a solid and thorough education on virology as it applies mainly to human diseases. While scientists have long suspected that there were infectious particles we now know to be viruses causing some human infections, the actual finding of viruses, their structures, and functions have been relatively recent because of medical research. In recent years, there has been an explosion of what medical researchers and doctors know about viral diseases and their effect on human health, leading to interventions that have greatly reduced the impact of these types of infections on our lives.

In this audio-course, the focus will be on how viruses cause disease, the human host response to viral infections, and the pathophysiology of the many different viral infections that affect all humans throughout the world. Many viruses are wellestablished and have caused the same known infections for millennia, while others are novel infections that continue to cause epidemics and pandemics, even in the modern medical era when we think we have the answers to all types of human diseases. Some viruses cause cancer because of their effect on the human cell genome, while others are used to treat human diseases in unique ways. We will also talk about the different approaches to managing viral infections, such as antiviral drug therapy and immunizations used to provide primary intervention against viral diseases.

Chapter one in the course introduces the study of viruses and virology by looking at what viruses are, how we have come to understand them, and how it is believed that viruses fit into the evolution of life on earth. Viruses have different structures and several choices in the types of genetic material in them that affect how they behave in an infection. In this chapter, we will also talk about the taxonomy of viruses as well as about the typical viral life cycle during a cellular infection.

Chapter two furthers the discussion of viruses by looking at viral infections in general. The basics of viral pathogenesis are discussed along with the typical immune response to viral infections, which leads to the majority of symptoms. Viruses with different

portals of entry lead to different host infectious diseases, which are also covered. The ways that viral infections are detected, called viral diagnostics, is also covered in this chapter.

The focus of chapter three in the course is the different types of DNA viruses as they apply mainly to human diseases. These include papovavirus infections, which include polyomaviruses and papillomaviruses, which share some common characteristics. Adenovirus infections also involve DNA viruses and herpesviruses are also major sources of DNA viral infections. We will also talk about poxviruses and parvoviruses, which aren’t as common in humans but still represent classifications of DNA viruses.

Chapter four is about the different positive-strand RNA viruses plus the various doublestranded RNA viruses causing human diseases. These include the different picornaviruses, such as poliovirus and other enteroviruses, coxsackie viruses, flaviviruses, and togaviruses. Coronaviruses are also positive-strand RNA viruses that can lead to both minor and severe respiratory infections. A variety of double-stranded RNA viruses cause human diseases, including rotaviruses and several tick-borne viruses. Each of these is covered in this chapter in terms of their clinical presentation and the pathophysiology of their disease processes in humans.

Chapter five in the course focuses on the different negative-strand RNA viruses, which are otherwise a diverse group of viruses. Filoviruses are discussed, including those that cause hemorrhagic diseases in humans. Influenza viruses, which are much more common causes of human disease, are also covered in this chapter. Rabies is a rhabdovirus that also causes severe disease in humans. There are several paramyxoviruses covered in this chapter, including those that cause mumps, measles, and respiratory syncytial virus infections.

The two main topics of chapter six are the reverse transcribing viruses called retroviruses and the different hepatitis viruses. Among reverse transcribing viruses are the retrovirus that causes HIV disease and human T cell leukemia viruses. Hepatitis viruses can be picornaviruses, such as hepatitis A or Hepadnaviruses, such as hepatis B and hepatitis C, which are discussed in this chapter. There are several minor types of hepatitis viruses, which are also covered in the chapter.

Chapter seven in the course talks about viral genome mutations and how these are most likely to occur. Certain viral genomes are more likely to be mutagenic than others, which has implications for viral epidemics and the evolution of viral pandemics. Viral mutations in both humans and animals are important factors in the development of novel viruses that become problematic in humans who do not have the immunity to the new form of the virus.

Chapter eight looks more carefully at issues related to virus epidemiology. A great deal about the epidemiology of viruses and their epidemics can be learned from past epidemics and pandemics. In this chapter, we talk about the different recent viral pandemics in the world and the ways in which each was unique as well as how each was handled. The ways in which viral epidemics are studied is discussed in this chapter, as well as commonly used terminology in epidemics, such as the basic reproductive number and the issues of antigenic drift versus antigenic shift.

Chapter nine in the course introduces satellite viruses or viroids and prion diseases, which are both representative of infectious particles that are considered to be subviral in their presentation. Subviral particles like viroids cannot reproduce by themselves and often need a helper virus in order to be infectious in humans. The chapter also talks about prion diseases, which can be infectious to humans. Prions contain no genetic material; their infectious component is made from an abnormal protein that causes disease in the cells they occupy.

Viruses have medical applications as one of several vectors used to treat diseases, which is the main focus of chapter ten. It involves making recombinant DNA technology that combines human genes with viral genomes for different purposes. These gene products can be used to make DNA libraries used for cloning and to used viral infections to add missing genes to a cell, such as would be used for the different gene therapies being studied throughout the world in the management of common single-gene disorders.

Chapter eleven in the course discusses issues seen in persistent viral infections and in infections secondary to tumor viruses, which have the potential to cause cancer or tumors in the cells they infect. As you will see, certain viruses are more prone to causing

persistent infections than others. The same is true for viruses that seem more likely to cause tumors or cancer compared to other viruses.

The focus of chapter twelve includes the different methods by which doctors and epidemiologists use viral detection strategies to detect an active or resolved viral infection. There are techniques used in acute situations and others that can say if an infection has largely resolved. The different antiviral therapies, including vaccines are covered in this chapter. Ideally, viruses that can be eradicated should be managed this way but it hasn’t been done in the vast majority of viral infections.