VI.Viral Diseases A.Influenza B.Diseases Caused by the Herpes Family C.Viral Hepatitis D.Human Immunodeficiency Virus E.Miscellaneous Viral Diseases

VI.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

VI.A.Influenza Symptoms & Complications of Influenza –Respiratory Tract Symptoms –Fever –Neurological Complications: Guillain-Barré Syndrome Reye’s Syndrome

VI.B.Diseases Caused by the Herpes Family 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

VI.B.Diseases Caused by the Herpes Family 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

VI.B.Diseases Caused by the Herpes Family Herpes Simplex (cont.) –Other complications Herpes encephalitis Congenital herpes Cervical cancer –Treatment: Acyclovir

VI.B.Diseases Caused by the Herpes Family Chicken pox & Shingles –Cause: Varicella-zoster virus –Chicken pox symptoms –Shingles symptoms –Treatment –Chicken pox vaccine –Connection to Reye’s syndrome

VI.B.Diseases Caused by the Herpes Family 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??!?

VI.B.Diseases Caused by the Herpes Family 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

VI.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

VI.C.Viral Hepatitis Hepatitis A (cont.) –Transmission: Virus particles are present in the stool Fecal-oral route via contaminated food or water Saliva contact, sexual contact, and arthropods also have been implicated

VI.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

VI.C.Viral Hepatitis Hepatitis A (cont.) –Treatment & Prevention: Prolonged rest Hepatitis A Immune Globulin Hepatitis A vaccine

VI.C.Viral Hepatitis Hepatitis B –Also known as: Serum hepatitis Long-incubation hepatitis

VI.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

VI.C.Viral Hepatitis Hepatitis B (cont.) –Transmission: Contact with infected body fluids Blood, blood products, semen, vaginal secretions (urine, saliva also implicated)

VI.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: months About 10% of patients remain carriers for several months

VI.C.Viral Hepatitis Hepatitis B (cont.) –Treatment & prevention Hepatitis B Immune Globulin Hepatitis B vaccination

VI.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

VI.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

VI.D.Human Immunodeficiency Virus 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

VI.D.Human Immunodeficiency Virus 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

VI.D.Human Immunodeficiency Virus Transmission –Contact with infected body fluids –Blood, blood products, semen, vaginal secretions, breast milk

VI.D.Human Immunodeficiency Virus 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

VI.D.Human Immunodeficiency Virus CDC Case Surveillance Definition for AIDS –Based on: Clinical Symptoms: Categories A, B, C Helper T-4 lymphocyte count: Categories 1, 2, 3 –Category A Asymptomatic HIV infection Persistent Generalized L ymphadenopathy Acute HIV infection

VI.D.Human Immunodeficiency Virus CDC Case Surveillance Definition for AIDS (cont.) –Category B Symptomatic HIV infection with constitutive illness & certain opportunistic infections Often an early indication that AIDS is developing –*Category C Symptomatic HIV infection with opportunistic infections listed in the CDC surveillance case definition

VI.D.Human Immunodeficiency Virus CDC Case Surveillance Definition for AIDS (cont.) –Category 1 T-4 count greater than 400 per microliter of blood –Category 2 T-4 count between 400 and 200 per microliter of blood –*Category 3 T-4 count less than 200 per microliter of blood

VI.D.Human Immunodeficiency Virus CDC Case Surveillance Definition for AIDS (cont.) –*These categories (C and 3) meet the CDC surveillance definition to be included among the AIDS cases –Many HIV-infected individuals show no symptoms, yet are capable of transmitting the virus

VI.D.Human Immunodeficiency Virus 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

VI.D.Human Immunodeficiency Virus Symptoms & Secondary Infections Associated with AIDS (cont.) –Constitutive Illness Weight loss, persistent fever, diarrhea –Cancers Kaposi’s sarcoma Certain lymphomas

VI.D.Human Immunodeficiency Virus Symptoms & Secondary Infections Associated with AIDS (cont.) –Bacterial Secondary Infections Mycobacterium Listeria Salmonella Mycoplasma many others

VI.D.Human Immunodeficiency Virus Symptoms & Secondary Infections Associated with AIDS (cont.) –Fungal Secondary Infections Candida and others –Protozoan Secondary Infections Toxoplasma gondii Cryptosporidium Pneumocystis carinii

VI.D.Human Immunodeficiency Virus Symptoms & Secondary Infections Associated with AIDS (cont.) –Viral Secondary Infections Herpes simplex Cytomegalovirus Many others Treatments –Inhibitors of DNA replication –Protease Inhibitors

VI.E.Miscellaneous Viral Diseases Miscellaneous Pneumotrophic Viruses –Rhinovirus –Adenovirus –Respiratory Syncytial Virus

VI.E.Miscellaneous Viral Diseases Miscellaneous Dermotrophic Viruses –Measles (Rubeola) –Rubella –Mumps –Fifth disease –Papilloma (HPV)

VI.E.Miscellaneous Viral Diseases Miscellaneous Viscerotrophic Viruses –Enterovirus (Coxsackie & Echo Viruses) –Rotavirus –Norwalk Virus

VI.E.Miscellaneous Viral Diseases Miscellaneous Neurotrophic Viruses –Poliomyelitis –Rabies –Arbovirus –Arenavirus (lymphocytic choriomeningitis)

VI.E.Miscellaneous Viral Diseases Prion Diseases –Bovine Spongiform Encephalopathy –Scrapie –Creutzfelt-Jakob Syndrome –Kuru