respiratory viruses -2013 (fn) [compatibility mode].pdf

7/30/2019 Respiratory Viruses -2013 (FN) [Compatibility Mode].pdf

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Dr F Noordeen

Department of Microbiology

Faculty of Medicine

PeradeniyaMay 2013


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Modes of transmission and the pathogenesis of

respiratory viral infections in humans

Clinical features of respiratory viral infections

Principles of diagnosis, management and prevention

of respiratory viral infections

Learning outcomes


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Aim: Make students aware pathogenesis andclinical significance of respiratory viruses

Objectives:

1. to diagnose respiratory virus infections

(aetiological diagnosis in the lab)

2. to prevent/control them in Sri Lanka


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ORTHOMYXOVIRUSESInfluenza virus - A, B and C

Influenza - Specific clinical syndrome

Epidemics - Since ancient times

Outbreaks - Significant morbidity + mortality

Pandemic - 1918-1919 (20 million deaths) H1N1

- 1997 Asia (Hong Kong) H5N1

- 2009 Americas (Mexico) H1N1- 2010and Asia

- 2011 H1N1

- 2012 Sri Lanka H5N1

(Avian virus in a poultry farm in Bingiriya)


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INFLUENZA VIRUS 80-120 nm, Segmented RNA genome

Helical capsid symmetry and very pleomorphic

Classification

Groups - (matrix and NP)

Subtypes on N and H

Important surface antigens

Haemagglutinin (H) (surface polypeptide)

Neuraminidase (N) (enzyme glycoprotein)


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INFLUENZA VIRUS on EM


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PATHOGENESIS OF INFLUENZA

Antigenic drift and shift

Destruction of mucous glycoprotein

Attachment to respiratory cells

Damaged mucosa and altered clearing

mechanisms

Non immune populationNon immune population

Neuraminidase mediatedNeuraminidase mediated

HaemagglutininHaemagglutinin mediatedmediated

SecondarySecondary bacterial infectionsbacterial infections


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INFLUENZA CLINICAL SYNDROMES

Brief pro-drome of malaise and headache

Fever (abrupt onset), severe myalgia

Non productive cough Lasts 3 days and full recovery

COMPLICATIONS Respiratory - Pneumonia (viral /bacterial)

(S pneumoniae, S aureus

) CNS - Acute encephalopathy

- Post viral encephalitis

- Reyes syndrome


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LABORATORY DIAGNOSIS

Individual diagnosis - clinical

NPA Immunofluorescence (IF) stain

Cell culture

Sentinel surveillance

Laboratories established throughout the world

Detect influenza activity Look for changes in N and H

Predict outbreaks

Prepare stocks of appropriate vaccine


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PREVENTION

IMMUNIZATION

KILLED OR SUBUNIT VACCINE and GIVEN ANNUALLY

RISK GROUPSElderly

Institutionalised persons

Cardiac and respiratory compromised


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PARAMYXOVIRUS

RNA virus

156-300 nm

helical nucleocapsid

surface glycoproteins (H, N, F) and membrane protein

3 Genera

Morbillivirus - Measles virus

Paramyxovirus - Parainfluenza virus Pneumovirus - Respiratory Syncitial Virus (RSV)


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MEASLES VIRUS Common childhood exanthem

High fever and characteristic rash

Cough, coryza and conjunctivitis

Significant morbidity and mortality

Complications Pneumonia (60% mortality)

CNS - Encephalitis (15% mortality)- Subacute sclerosing panencephalitis (SSPE)

Appreciable drop in incidence since immunisation


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MEASLESMEASLES

DIAGNOSIS

1. Clinical - typical rash with fever

2. Laboratorya. Direct (NPA) - IF or EIA

b. Serology - Rise in antibody

- Measles specific IgM


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Kopliks spots


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PREVENTION Live attenuated vaccine

Introduced in 1963

Major impact on incidence of disease

Given at 9 months of age

Discussion - need for booster


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PARAINFLUENZA VIRUSES 4 serologic types

Older children & adults - mild to moderate URT

infection -cold

infants & children < 5 years

Lower respiratory tract infections

Laryngotracheobronchitis CROUP

Re-infections common - Only shortterm immunity

Laboratory diagnosis

Cell culture, IFA on NPA

IP 2- 6 days

Hoarseness

Seal bark cough

Tachypnoea

Tachycardia

Suprasternal

retraction


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RESPIRATORY SYNCYTIAL VIRUS (RSV)

First recovered in 1936

Most frequent cause of fatal acute respiratory infection in

infants and young children

Re-infections occur

Pathogenesis

Localised infection Bronchiolitis and Pneumonia

Vaccination increases severity of disease

Nosocomial transmission common


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IMMUNOFLUOROSCENCEOF NASOPHARYNGEAL

ASPIRATE FOR RSV


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MUMPS VIRUS

Cause of acute benign viral parotitis Epidemiology - world wide and endemic

Spread - direct -person to person

Virus present in respiratory secretions 7 days

before clinical illness

Clinical syndromes

Parotitis - usually bilateral

Orchitis - usaully unilateral

Oopheritis

Pancreatitis

CNS - Aseptic meningitis (50%)

- Encephalitis


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Papilla of parotid

gland in mumps


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CORONAVIRUS Strains from human and animals

Enveloped RNA virus

Optimum temperature 33-35C

Upper respiratory pathogen

5-15% of common cold

Also a GI pathogen


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The novel CORONAVIRUS

Aetiology - Quickly suspected to be a virus

March 2003 - 3 groups associated

CORONAVIRUS with SARS

Recovered this new virus from E 6 cells

Finding which surprised the scientists

There were no other respiratory pathogen includinghuman metapneumovirus

Association with the novel coronavirus + SARS agreed


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RNA viruses include1. Herpes Simplex 1

2. Epstein Barr virus

3. Hepatitis B virus4. Measles virus

5. Respiratory Syncytial Virus (RSV)


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Which of the diagnostic method is

appropriate for the stated infection

1. RSV - IF staining of NP secretions

2. Hepatitis A - isolation of virus from faeces

3. Hepatitis B - HBsAg detection in the serum

4. Chicken pox - EM examination of vesicle fluid

5. Measles - Rise in mumps antibody titre

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