Selected Viral Diseases Updated March 2015 J. D. Hendrix

Selected Viral Diseases

Updated March 2015

J. D. Hendrix

Selected Viral Diseases

A. Influenza

B. Diseases Caused by the Herpes Family

C. Viral Hepatitis

D. Human Immunodeficiency Virus

E. Miscellaneous Viral Diseases

A. Influenza• Properties

–Member of the Orthomyxovirus family –Enveloped RNA virus –Two envelope proteins

• Hemagglutinin and Neuraminidase

–Segmented RNA • 8 segments; packaged into helical nucleocapsids

–Antigenic variation & genetic exchange lead to the appearance of new strains; requires use of different vaccine combinations each year

A. Influenza

• Symptoms & Complications of Influenza–Respiratory Tract Symptoms –Fever –Neurological Complications:

• Guillain-Barré Syndrome • Reye’s Syndrome


• Properties of the Herpes Virus Family–Large, enveloped DNA viruses – Icosahedral capsids –DNA replicates in the nucleus of host

cells –Cells may become permanently infected –Host chromosomes may be altered –Herpes infections associated with certain

cancers


• Herpes Simplex–Two major strains

• Type I: Oral Herpes • Type II: Genital Herpes

–Skin lesions form at site of the infection –Virus travels along sensory neurons to

ganglia, where it remains –During times of stress or weakened

immunity, virus may travel along same neurons to re-infect the initial skin sites


• Herpes Simplex (cont.)–Other complications

• Herpes encephalitis • Congenital herpes

–Treatment: Acyclovir


• Chicken pox & Shingles–Cause: Varicella-zoster virus –Chicken pox symptoms –Shingles symptoms –Treatment –Chicken pox vaccine –Connection to Reye’s syndrome


• Infectious mononucleosis–Cause: Epstein-Barr virus – Infectious mononucleosis –Lymph node swelling; fever; fatigue –Heterophile antibody production –Monospot Test –Other complications

• Burkitt's Lymphoma • Chronic Fatigue Syndrome??!?


• Cytomegalovirus–Mild symptoms in otherwise healthy

individuals –Major complications

• Miscarriages when contracted during pregnancy

• Severe infections in AIDS patients • Major cause of blindness in AIDS patients

C. Viral Hepatitis

• Hepatitis A–Also known as:

• Infectious hepatitis• Short-incubation hepatitis

–Viral Properties• Picornavirus Family• Small nonenveloped RNA viruses• Family includes common cold (rhinovirus)

& polio viruses

C. Viral Hepatitis

• Hepatitis A (cont.)–Transmission:

• Virus particles are present in the stool• Fecal-oral route via contaminated food or

water

C. Viral Hepatitis

• Hepatitis A (cont.)–Symptoms:

• Two to four week incubation period• Nausea, vomiting, fever• Abdominal pain• Jaundice in many but not all cases• Duration usually several weeks

C. Viral Hepatitis

• Hepatitis A (cont.)–Treatment & Prevention:

• Prolonged rest• Hepatitis A Immune Globulin• Hepatitis A vaccine

C. Viral Hepatitis

• Hepatitis B–Also known as:

• Serum hepatitis• Long-incubation hepatitis

C. Viral Hepatitis

• Hepatitis B (cont.)–Viral properties:

• Hepadnavirus family• Nucleocapsid consists of DNA surrounded by

hepatitis B core antigen (HBcAg)• The core is surrounded by a lipoprotein envelope

containing the hepatitis B surface antigen (HBsAg)• The virus has also been called the Dane particle• Large amounts of excess HBsAg are found in the

serum & may be detected serologically

C. Viral Hepatitis

• Hepatitis B (cont.)–Transmission:

• Contact with infected body fluids• Blood, blood products, semen, vaginal secretions

C. Viral Hepatitis

• Hepatitis B (cont.)–Symptoms:

• Incubation period: four weeks - six months• Nausea, fever• Dark urine & clay-colored stools• Abdominal tenderness• Jaundice• Duration of symptoms: 3 - 4 months• About 10% of patients remain carriers for several

months

C. Viral Hepatitis

• Hepatitis B (cont.)–Treatment & prevention

• Hepatitis B Immune Globulin• Hepatitis B vaccination

C. Viral Hepatitis

• Non-A non-B (NANB) Hepatitis–Hepatitis C

• NANB serum hepatitis• Enveloped virus of the Flavivirus family• Transmission & symptoms similar to B

–Delta hepatitis• A small defective RNA virus that requires

coinfection with Hepatitis B to replicate• Co-transmitted with Hepatitis B

C. Viral Hepatitis

• Non-A non-B (NANB) Hepatitis (cont.)–Hepatitis E

• NANB infectious hepatitis• A small nonenveloped RNA virus of the calcivirus

family• Transmission & symptoms similar to Hepatitis A


• Viral Properties– A retrovirus– An enveloped RNA virus that replicates through

a DNA intermediate– The DNA intermediate is synthesized by reverse

transcriptase: an enzyme that makes a DNA molecule using an RNA template

– The DNA intermediate is spliced into host chromosomes, making the infection permanent


• Viral Properties (cont.)– Host cells for HIV: CD4+ cells– Helper T (T-4) lymphocytes– Macrophages– Damage to the helper T cell population cripples

the immune system of the host


• Transmission– Contact with infected body fluids– Blood, blood products, semen, vaginal

secretions, breast milk


• What is the difference between HIV & AIDS?– HIV: the Human Immunodeficiency Virus

• The cause of AIDS

• Also known as: HTLV-III and LAV • Two known types: HIV-1 and HIV-2

– AIDS: Acquired Immune Deficiency Syndrome• Catastrophic immune system failure caused

by HIV infection • Symptoms & cases are usually defined by the

CDC case surveillance definition


• Symptoms & Secondary Infections Associated with AIDS

– Acute Infection• Fever, lymph node swelling, aches, fatigue,

“flu-like” or “mono-like” symptoms– Persistent Generalized Lymphadenopathy

• Lymph node swelling for greater than 6 months in two or more body areas (excluding the groin)

• Often an early manifestation that AIDS has developed


• Symptoms & Secondary Infections Associated with AIDS (cont.)

– Constitutive Illness• Weight loss, persistent fever, diarrhea

– Cancers• Kaposi’s sarcoma• Certain lymphomas



– Bacterial Secondary Infections• Mycobacterium• Listeria• Salmonella• Mycoplasma• many others



– Fungal Secondary Infections• Candida and others

– Protozoan Secondary Infections• Toxoplasma gondii• Cryptosporidium• Pneumocystis carinii



– Viral Secondary Infections• Herpes simplex• Cytomegalovirus• Many others

• Treatments– Inhibitors of DNA replication– Protease Inhibitors


• Miscellaneous Pneumotrophic Viruses– Rhinovirus– Adenovirus– Respiratory Syncytial Virus


• Miscellaneous Dermotrophic Viruses– Measles (Rubeola)– Rubella– Mumps– Fifth disease– Papilloma (HPV)


• Miscellaneous Viscerotrophic Viruses– Enterovirus (Coxsackie & Echo Viruses)– Rotavirus– Norwalk Virus


• Miscellaneous Neurotrophic Viruses– Poliomyelitis– Rabies– Arbovirus– Arenavirus (lymphocytic choriomeningitis)


• Prion Diseases– Bovine Spongiform Encephalopathy– Scrapie– Creutzfelt-Jakob Syndrome– Kuru

Documents

Selected Viral Diseases Updated March 2015 J. D. Hendrix