Download II. Classification of Microorganisms

VI.
A.
B.
C.
D.
E.
Viral Diseases
Influenza
Diseases Caused by the Herpes Family
Viral Hepatitis
Human Immunodeficiency Virus
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: 3 - 4 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