Viral Diseases – Part I Respiratory and Skin Diseases Nestor T. Hilvano, M.D., M.P.H.

Viral Diseases – Part I Respiratory and Skin Diseases

Nestor T. Hilvano, M.D., M.P.H.

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- 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)

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 (one-

sided 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 viruses1. 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 viruses5. 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. Discuss the structure of virus, its ability to cause

infections, and latency of virus. 2. 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.

3. Describe clinical manifestations of measles and ways of preventing them.

4. Discuss antigenic drift and antigenic shift of influenza virus.