Infection of Respiratory Tract. Introduction, morphology, pathogenesis, symptoms, diagnosis.

 The respiratory tract comprises of upper and lower tract. There are different organisms infecting the upper respiratory tract and lower respiratory tract. The organisms of URI ( upper respiratory tract infections) are Streptococci groups, cornea bacterium diphtheria, Borrelia, Adenovirus, Rhinovirus, mumps infection.

The organisms of lower organism Klebsiella pneumoniae, pseudomonas, mycoplasma, etc 

Introduction

Influenza is categorize in URI ( upper respiratory tract infection). It comes under family Orthomyxoviridae. This is a envelope RNA virus. 

Morphology

Influenza is an acute infectious disease. The influenza virus is usually spherical with diameter 80-120 nanometer. Some strains show pleomorphism (shapeless). 

The influenza virus has a lipid envelope. The envelope contain two types of glycoprotein spikes- Hemagglutination (HA) facilitate viral attachment to the host cells & entry, Neuraminidase (NA)- it assist in the release of newly form from infected cells. 

There are surface membrane protein known as M proteins. This M protein contains M1 & M2. So M1 provide structural integrity & M1 is the ion channel.

 The influenza viruses are classified into 3 seri types i.e A, B, C based on different antigen.

Pathogenesis

The pathogenesis of influenza virus in human involves various following steps:-

1. Viral Entry :- The virus is transmitted via respiratory droplets or contact with contaminated surface. 

2. Attachment :- The viruses attaches to & penetrate respiratory epithelial cells in the upper & lower respiratory tract. This attachment is mediated by the interaction between the viral Hemagglutination (HA) protein & sialic acids on the host cell surface. 

3. Replication of virus :- The virus replicate in the respiratory tract destroying the host cells. 

4. Immune response :- there is a immune respons with release of pro-inflammatory cytokinase.

eg. IL-6 (Interleukin-6), interferons. 

Clinical symptoms

• Fever - it starts with on set of fever, headache, sore throat and cough. 

• Abdominal pain and vomiting may occurs. 

• In severe cases the individual might  suffer of breathless or shortness of breath. 

• In young children compilation such as otitis media or bronchiolites, dehydration, etc. 

Laboratory diagnosis

1. Specimen collection, sputum. 

2. Sore throat. 

3. Rapid diagnosis of influenza by demonstrating virus antigen on the surface of nezofaringles cells by immunofluorescence. 

4. RT-PCR ( reverse transcription polymerase chain reaction) this test is consider as gold standard for diagnosing influenza it involves extracting viral RNA from clinical specimen then amplify the PCR product. 

5. NAAT ( Nucleic acid amplification test) :- This test is used for influenza diagnosis with amplification RNA. NAAT is a highly sensitive and specific diagnostic method used to detect and amplify genetic material (DNA or RNA) of pathogens, cells, or other biological entities.

6. Direction fluorescent antibody test :- is it also known as immunofluorescent antibody test, is an antigen based test routinely employed for diagnosis of influenza viral infection. 

Isolation of virus/ viral cultural

Virus isolation is achieved during first two- three days during illness and cultured in primary monkey kidney cell. 

Hemagglutination :-

This test provide convince fir the detection of influenza virus in egg and other culture fluid. 

Prevention

° Vaccine – IIV inactivated influenza vaccines, killed vaccine, recombinant vaccine, sub-unit vaccine. 

° Person hygiene. 

Treatment

Antiviral drugs – Baloxavirus, Relenza - designed to block viral neuraminidase ( is a glycoprotein enzyme present on the surface of influenza virus & plays a crucial role in a virus lifecycle.