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 (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 ˚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.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.