Clinical Virology: Part Two
The Viruses
MLAB 2434 – Microbiology
Keri Brophy-Martinez
Respiratory Viruses
• Influenza Viruses
– ssRNA virus
– Causes crucial health problems
• epidemics and pandemics
– Antigenic drifts and shifts
• Major or minor changes in viral surface
glycoproteins
– Attack ciliated epithelial cells of
respiratory tract
Respiratory Viruses(cont’d)
• Parainfluenzae Viruses
– Enveloped RNA
– Major cause of respiratory disease in young
children
• Respiratory Syncytial Virus (RSV)
– Enveloped RNA
– Most common virus isolated from infants with LRT
infections
– Spread by contact with respiratory secretions
Respiratory Viruses(cont’d)
• Adenoviruses
– Half of all infections are asymptomatic
– Causes 10% of all pneumonia cases
– Causes 5% - 15% of all gastroenteritis in
children
– dsDNA, nonenveloped
Respiratory Viruses (cont’d)
• Rhinoviruses
– Major cause of common cold
– Infect nasal epithelial cells and activate
inflammatory response
– ssRNA, small and naked
– No cure
• Coronaviruses
– ssRNA
– Cold-like infections
Exanthemas
• Definition = skin eruption
accompanying certain
infectious diseases
• Mumps
– ssRNA
– Swelling of parotid
glands, testes, ovaries
and pancreas
– Vaccine available
Exanthemas (cont’d)
•
Measles (Rubeola)
– ssRNA virus
– Abrupt onset with sneezing, runny
nose and cough, red eyes and high
fever, followed by maculopapular
(flat discolored area of skin with
raised bump) rash on head and
trunk
– Also see Koplik’s spots- bright
red spots with white centers
– Easily diagnosed clinically; lab
requests rare
Exanthemas (cont’d)
• Rubella
– Enveloped ssRNA
– Mild febrile illness with rash and lymphadenopathy;
many cases asymptomatic
– Rash starts on face and spreads to trunk and
limbs; no rash on palms and soles
– Causes birth defects in first trimester
– Vaccine strongly recommended
– Serologic titer for immune status
Exanthemas (cont’d)
• Parovirus B19
– ssRNA
– Causes Erythema
Infectiosum, also
known as “Fifth
Disease”
– “Slapped cheek”
appearance,
spreading to trunk
and limbs
Immunodeficiency Viruses
• Human Immunodeficiency Virus Type 1
– AIDS
– ssRNA
– Target cells are CD4+ T cells
– Destruction of these cells results in
opportunistic infections
Central Nervous System
Viruses
• Enteroviruses
– ssRNA virus
– Includes poliovirus, coxsackie A and B, and
echovirus
– Transmission: Fecal-oral/respiratory
– Causes a variety of infections and conditions,
including paralysis
– Resistant to disinfectants
Agents of Gastrointestinal
Infections
• Known to cause the “stomach flu”
• Includes adenovirus, norovirus, rotavirus
• Rotaviruses
– dsRNA with double-layer protein capsid
– Most common cause of gastroenteritis in
infants, children
– Oral-fecal route
– Hand washing and vaccines for prevention
Agents of Gastrointestinal
Infections (cont’d)
• Norovirus
– Originally called Norwalk and Norwalk-Like Agents
– Gastroenteritis in older children and adults
– Outbreaks in camps, schools, and on cruise ships
– Nausea, vomiting, diarrhea and low-grade fever
– Highly infectious
Family Arenaviridae
• Causes hemorrhagic fevers
– Lassa Fever
• Transmitted by rodents
• Acquired by aerosol or skin abrasion
Family Filoviridae
• Includes Ebola and Marburg viruses
• Human infections may result from
contact with infected monkeys
• High mortality rates
• Unknown reservoirs in nature
Rabies
• Transmitted by bite or scratch from infected
animal
• Pain at site of infection, followed by flu-like
symptoms
• CNS system changes, followed by death
• Vaccine and postexposure prophylaxis available
• Detected in brain of source animal
Human Papilloma Virus
• dsDNA virus
• Causes
– Leading cause of sexually transmitted
disease
– Common and plantar warts
– Genital warts
– Associated with cervical cancers
Hepatitis Viruses
• Hepatitis A (HAV)
– oral-fecal
– Person-person contact, contaminated
food/water
– RNA
– Anti-HAV antibodies emerge around 10
days
Hepatitis Viruses

Hepatitis B (HBV)
 Blood and body
fluids
 DNA
 Hardy organism
Hepatitis Viruses
• Hepatitis C (HCV)
– Blood and body fluids
– RNA
– For diagnosis- Anti-HCV serology
• Hepatitis D (HDV)
– Blood and body fluids
– RNA
– Requires HBV for replication
• Hepatitis E (HEV)
– Oral-fecal
– RNA
Herpesviruses
• HSV Type 1
–
–
–
–
Oral herpes
“Cold sores”
Can cause encephalitis
Recurrent
• HSV Type 2
–
–
–
–
Genital herpes
Neonatal herpes
Can cause encephalitis
Recurrent
Herpesviruses (cont’d)
• Varicella-zoster
– Varicella causes chicken pox
– Zoster is clinical manifestation of reactivated
varicella virus, which can be latent in nerve tissue
(“Shingles”)
• Epstein-Barr
– Mononucleosis
– Associated with Burkitt’s lymphoma,
nasopharyngeal carcinoma, Hodgkins lymphoma
Herpesviruses (cont’d)
• Cytomegalovirus (CMV)
– Most common congenital infection in U.S.
– Most adults have antibodies to CMV
• Herpesvirus 6
– Causes Roseola Infantum or “Sixth Disease”
Herpesviruses (cont’d)
• Herpsevirus 7
– Infects CD4 + cells
– Viruses present in 75% of adult saliva
• Herpsevirus 8
– Detected in Kaposi’s sarcoma
– Not culturable
Arboviruses
• Derive name from mode of transmission
(arthropod born)
• Humans are dead-end hosts
• Families
– Bunyaviridae family
• Vector- mosquito
• Hemorrhagic fever, including Hanta virus
• Encephalitis
Arboviruses (cont’d)
• Togaviridae family
– Encephalitis
• Reoviridae family
– Colorado tick fever
• Flaviviridae family
– Most common cause of arboviral encephalitis in the
world, including St. Louis encephalitis (SLE)
– West Nile
– Dengue fever (Classic and hemorrhagic)
– Yellow fever
Antiviral Therapy
• Like bacteria and antibiotics, the use of
antivirals can result in virus resistance
• Some viral infections are treatable,
especially if therapy is given early in
infection
• Antivirals must be designed to target a
viral replication mechanism without
destroying host cells
• Vaccinations
References
•
•
•
•
•
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Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory Microbiology:
A Practical Approach . Upper Saddle River, NJ: Pearson Education.
Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic
Microbiology (4th ed.). Maryland Heights, MO: Saunders.
http://www.fifthdisease.org/general.html
http://www.idph.state.il.us/about/immunepics/measles.htm
http://www.idph.state.il.us/about/immunepics/mumps.htm
http://www.mc3cb.com/viruses.html