Viral Diseases – Part I
Respiratory and Skin Diseases
Nestor T. Hilvano, M.D., M.P.H.
Images Copyright by Bauman, Robert. 2009. Microbiology, With
Diseases by Taxonomy, 3rd edition, Pearson Benjamin Cummings
Learning Objectives
You should be able to:
1. Discuss the structure and function of the virion.
2. Compare and contrast replication cycle of
viruses and with latency.
3. Describe the respiratory diseases caused by
Adenovirus , Rhinovirus, Coxsackie virus A
and B, Influenza virus A and B, and
Coronavirus.
4. Discuss the occurrence of Reye’s syndrome.
5. Describe the common viral skin diseases as to
its cause and clinical manifestations.
Viruses
• Acellular agent
• Viral structure and components
- Nucleic acids
Polyhedral capsid
- With protein coat (capsid); Some
have phospholipid membrane (envelope)
• Viral infection (direct penetration, membrane fusion,
endocytosis)
- affinity of protein or glycoprotein
on surface of host cell
- viral replication within host cell
- lysis of host → viremia → immune response
• Latency – remain dormant; no lysis of host
cells (lysogeny)
Lytic Viral Replication
Respiratory Viruses: Most Common Viral
Infection
DNA Viruses
•Adenovirus – common colds
RNA Viruses
•Rhinovirus – common colds
•Coxsackie virus A– upper respiratory infection
•Coxsackie virus B – pleuritis
•Influenza viruses A and B – common flu
•Coronavirus – SARS (Sever Acute Resp.
Syndrome)
•Reye syndrome
Adenovirus
• dsDNA virus
• Via respiratory droplets
• Survive on fomites and
improperly chlorinated
waters
• One of the agent of common colds; epidemics in
military bases
• Also cause mild diarrhea in children; and pink
eye
Rhinovirus
• RNA virus; limited to URTI (common cold)
• Via direct contact (aerosols, hand-hand contact),
fomites
• Adults can acquire herd immunity to specific
serotypes (community immunity w/o receiving vaccines
)
• Preventive measures – to limit spread by
antisepsis; disinfection of fomites
What is the most common cause of colds?
a. Adenovirus
c. Rhinovirus
b. Coxsackie virus
d. Influenza virus
Respiratory Syncitial Virus
• Cause infection of the lungs and resp. tract;
prevalent in US (65%-98% of children in day
care by age 2)
• MOT: direct hand contact; fomites
• Lead to respiratory disease in infants and
young children – bronchiolitis and pneumonia
(could be fatal)
• Older children and adults – asymptomatic or
mild cold
• Prevention – good hygiene
Coxsackie A virus
• RNA virus
• Transmitted by fecal-oral route
(enterovirus)
• Spread via blood (viremia)
• Lesions and fever – self-limiting
• Lesions of mouth and
pharynx – herpangina,
accompanied by sorethroat, fever
• Cause hand- foot- and- mouth
disease
• Complication – viral meningitis
(self-limiting above 1 yr. old)
Coxsackie B Virus
• RNA virus
• Fever associated with pericardial infection (onesided severe thoracic pain), and myocarditis
• Implicated in insulin- dependent DM, and
• Guillain- Barre syndrome = autoimmune;
demyelination of PNS resulting to temporary
paralysis
• Viral meningitis (self-limiting)
• Prevention – good hygiene and adequate
sewage treatment
Influenza viruses (A and B)
• Caused epidemics; flu pandemic in US 1918-19 (50
millions died); attack cells of lungs
• ssRNA virus; Species of orthomyxoviruses
• Infection primarily thru inhalation and also fomites
• Enter lung by glycoprotein spikes- hemagglutin
(triggers pulmonary cells endocytosis) and
neuraminidase (hydrolysis mucus in lungs)
• Mutation – antigenic drift (within a single strain
every 2 yrs.) and antigenic shift (from different
strains every 10 yrs.)
• Vaccine – 70% effective against selective strains;
flu vaccines (deactivated viruses)
Reye Syndrome
• Mechanism (exact cause) is unknown
• Affect children and teenagers after recovering
from viral infections (flu or chicken pox);
associated with aspirin intake to treat viral
infection
• Systemic (Serious) condition causing swelling of
liver & brain: Fatty change in liver; Edematous
encephalopathy in brain
• Fatal – 30% mortality in US (1981 – 1997)
Coronavirus
• single-stranded RNA virus
• Envelope with corona-like halos around helical
capsid
• Transmitted via droplets; spread by close
contact
• Second common cause of Colds
• SARS – fever (above 100.4 ˚F), headache, and
respiratory distress; remain a potential problem
in China
• No antiviral Rx or vaccine is available
Viral Skin Diseases
DNA viruses
1. Poxviridae
- variola (smallpox); vaccinia (cowpox);
molluscipoxvirus (molluscum contagiosum)
2. Herpesviridae
- herpes simplex I and II
3. Varicella zoster virus (chicken pox/ shingles)
4. Papillomavirus (wart)
RNA viruses
5. Rubeola (measles)
6. Rubella (German measles)
Smallpox (variola)
• Variola major (20% mortality) and
Variola minor (less than 1% mortality)
types
• Related to cowpox virus
• Last outbreak in lab causing disease
(1978)
• Virus inhaled (incubation of 12 days),
produce macules, vesicles, and
pustules
• Severe scars
• WHO – eradicated in 1980,factors:
effective vaccine; smallpox specific to
human, no animal reservoir; accurate
dx/quarantine; no asymptomatic case;
spread only via direct contact
Cowpox (vaccinia)
• Similar but milder than
smallpox
• Via direct contact with cows
• usually on hands and fingers; itchy
• Self-limiting to convalescence
• Imparts immunity for smallpox and
cowpox
Molluscum contagiosum
• Poxvirus
• Spread by contact with
infected children
• Smooth, waxy, tumor-like
nodules on face, trunk, and
limbs
• Papules in ano-genital area
(sexually active)
• Rx – removal by freezing or
chemicals
Herpes simplex I and II
• Herpes I – fever blisters or cold
sores on lips; gingivostomatitis;
herpetic pharyngitis; ocular or
opthalmic herpes (V CN)
caused by activation of latent
viruses
• Herpes II – usually genital
lesions
• Whitlow on finger –virus enters
the break on skin/finger
• Via physical contact – kissing,
sex, childbirth/ placental
• Complications – encephalitis,
meningitis, and pneumonia
• Prevention is important
Chicken Pox (varicella)
• Varicella- zoster virus
• Inhaled virus (incubation 2- 3 weeks)
• Vesicular rash from trunk to face and
limbs
• Convalescence – crust lesions
• Shingles (herpes zoster) – in adults
- from latent virus in nerves
- vesicular eruptions in dermatomes
- radiculoneuritis ( itching, burning,
pain)
- recurrence once/ twice after age 45
- Rx = symptomatic and bed rest;
acyclovair provide relief from
painful rash
• Prev. – attenuated vaccine for children
Common Wart
• Verruca virus
• Benign epithelial growth on
body surfaces
• Via direct contact, fomites
• autoinoculation
• Rx.- surgery, freezing,
cauterization, laser, or
caustic chemical
Venereal Wart
• Papilloma virus
• Genital warts ( over 500,000 new
cases reported each yr. in US)
• Range from tiny bumps, to
condyloma acuminata
• Associated with 70% risk of
cervical CA
• Circumcised men – reduced
incidence of cervical CA (43%)
• HPV (human papilloma virus)
vaccine is available –
controversial
• Prev. – abstinence
Measles (Rubeola)
• Contagious and serious childhood
diseases
• Via respiratory droplets
• Symptoms – fever, sore throat,
headache, dry cough, conjunctivitis,
photophobia
• koplik’s spot (red spot w/ whitish center in
mouth after 2 days of illness) – last 1-2 days
• Red raised (maculopapular) lesions then
appear on head (behind the ear, face) and
spread over the body
• Self –limiting; immunity
• Complication – pneumonia, encephalitis,
SSPE (subacute sclerosing panencephalitis)
• Vaccine (live, attenuated) available
German Measles (Rubella)
•
•
•
•
•
•
Rubella virus
Via respiratory droplets
Flat, pink to red (macule) rash
3 day measles
rarely fatal even in adults
Pregnant women – cause severe
birth defects
- cataract; deafness; mental
retardation; heart diseases
(tetralogy of Fallot);
microcephaly, growth retardation
• Vaccine (live, attenuated) –
decreased incidence
Homework
1.
2.
3.
4.
Discuss the structure of virus, its ability to cause
infections, and latency of virus.
Identify the viral agent of the following: common cold
with conjunctivitis; hand-foot-mouth disease in china;
common cause of rhinitis (colds); respiratory disease
in infants and young children
(bronchiolitis/pneumonia); pleuritis; flu virus; SARS;
oral sores and genital lesions; common wart; venereal
wart; Reye’s syndrome; varicella and shingles;
rubeola; 3 day measles.
Describe clinical manifestations of measles and ways
of preventing them.
Discuss antigenic drift and antigenic shift of influenza
virus.